chapter 4 section 4.2 : physical & chemical properties ...nov 04, 2018 · plastic, diamond, road...

Chapter 4 Section 4.2 : Physical & Chemical Properties.notebook1
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https://www.youtube.com/watch?v=C4pQQQNwy30
Plastic, diamond, road salt, and table salt are different types of matter with their own special properties. Understanding the properties of matter helps us to work safely with different substances and to change them to make useful things.
All matter has specific physical and chemical properties.
A physical property is a characteristic of a substance that can be observed with your senses or measured.
Physical properties can be: qualitative (nonnumerical) or quantitative (involving numbers).
Examples of Physical Properties: • state (solid, liquid, gas) • color • lustre • conductivity • density (mass per unit volume) • ductility • malleabililty • hardness • viscosity • melting/boiling point • mass
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Chemical properties describe how substances behave when combined with other substances.
Examples: • Reacts with water • Reacts with acid • Combustible solids or liquids which are able
to catch fire and burn easily. • Toxicity the level of harm a toxin can cause
an organism. • Flammable liquids will ignite & burn at
normal working temperatures. • Emits heat or light during reaction
Section 4.2: Physical & Chemical Properties p. 148‐155
Summary:
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Questions to think about before watching the video.
1. How does the metal • react with oxygen? • react with water?
2. Is there any difference in the reactions? If so, what caused the difference?
3. Which variables were controlled in this experiment? Why?
https://www.youtube.com/watch?v=eaChisV5uR0
4.2 Physical & Chemical Change Practice.docx
1.7 Physical and Chemical Changes and Examples.pdf
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Atoms, Elements, and Compounds Atoms, Elements, and Compounds
Each of these octopus- like structures has a tiny metal head and “nanowire” arms made of silica. Silica is a common substance with useful characteristics. It is, for example, a major part of sand and glass. Silica nanowires, shown here magnified about 20 000 times, can be used in communications devices.
U N I T
Unit Task
Every substance has special properties that may make it useful or hazardous or both. In this unit, you will learn about the components that make up different substances and give them their unique properties. In your Unit Task, you will design and test a toothpaste and investigate the properties of the ingredients that you use.
Essential Question What properties make one substance different from another?
Matter has physical and chemical properties.
4.1 Investigating Matter
4.2 Physical and Chemical Properties
The periodic table organizes elements by patterns in properties and atomic structure.
5.1 Developing the Atomic Theory
5.2 The Elements
6.1 How Compounds Form
6.2 Names and Formulas of Common Compounds
6.3 Balancing the Hazards and Benefits of Elements and Compounds DI
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DI
Contents
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We use plastic bags to carry groceries, package food, and contain garbage. When plastic bags are not recycled, they often become litter.
Plastic World Count the number of plastic items that you can see around you. People use plastic pens, cutlery, and bags. We use plastic in shoes, computers, cellphones, furniture, and cars. We use plastic to make food containers and the refrigerators they are stored in. There are many reasons that plastics are so widely used.
A plastic is a material that can be shaped when soft and then hardened. This characteristic is very useful. There are many different kinds of plastics. Some plastics are made into sturdy structures and can be used to replace or strengthen human body parts, such as a faulty heart valve. Other types are made into thin, flexible sheets, perfect for making bags. Many plastics do not break down easily. This characteristic is useful for making long- lasting structures, such as outdoor furniture, or items we use every day, such as household appliances. Plastic containers and gloves are very useful for safely handling corrosive chemicals. Chemistry helps us explore these and other characteristics of substances.
132 UNIT B Atoms, Elements, and Compounds
Exploring
We would need to make many changes in our everyday lives if we did not have plastics.
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133Exploring
The Lifetime of the Plastic Bag Plastic bags often end up as litter instead of being recycled. In some countries, so many plastic bags litter streets that the plastic shopping bag is known as “the national flower” or “the national flag.” Plastic bags have clogged storm drains, causing floods. The bags can also kill marine animals that eat them. For these reasons, and to save resources, many communities around the world have restricted the use of plastic bags.
A typical plastic shopping bag is made of polyethylene. Polyethylene is relatively inert, which means that it does not react easily with other chemicals. This makes polyethylene useful, but since it does not easily break down in the environment, care must be taken to reduce its use and to recycle or dispose of it responsibly.
The Town of Leaf Rapids, Manitoba, once spent thousands of dollars each year to clean plastic bags out of the forest. Bags scattered by the wind would cling to trees and fences near the town garbage dump. The town wanted a solution, and so Leaf Rapids became the first community in Canada to ban disposable plastic shopping bags.
B1
Do We Need Plastic Shopping Bags?
When we are finished using a plastic bag, we are faced with its disposal. Recycling is one option, but this uses energy and resources, possibly more than making the plastic bag in the first place.
Plastic bags and other polyethylene products often end up in landfill — or as litter — and may not break down for decades.
1. Should disposable plastic shopping bags be made illegal? Make a table with the headings “Advantages” and “Disadvantages.” Give your table a title. Identify at least two advantages and disadvantages of this idea. Decide your position, and defend your stance in a class discussion.
2. At 16 years old, Daniel Burd won the Canada-Wide Science Fair for discovering that a certain type of bacteria can degrade over 40 percent of the weight of plastic bags in less than 3 months. How could this discovery be applied to improve the environment?
3. Plastic bags are not only used for shopping. List three other common uses for plastic bags. Can plastic shopping bags be safely reused for these other purposes? Explain.
Science, Technology, Society, and the EnvironmentSTSE
Sea turtle eating a discarded plastic bag
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Matter has physical and chemical properties. 135
The same properties of water that cause it to form beads on the surface of a leaf allow water to form a column inside a plant's stem. The column of water stretches from the roots to the top of even the tallest trees.
Skills You Will Use In this chapter, you will:
• investigate and identify the physical and chemical properties of substances
• plan and conduct an inquiry into the properties of common substances
• conduct tests to identify gases
Concepts You Will Learn In this chapter, you will:
• assess the usefulness and hazards of polyethylene
• use appropriate terms to describe elements and compounds
• describe the physical and chemical properties of common elements and compounds
Why It Is Important Plastic, diamond, road salt, and table salt are different types of matter with their own special properties. Understanding the properties of matter helps us to work safely with different substances and to change them to make useful things.
The Language of Chemistry
Make a “Language of Chemistry” chart for the terms below. Your chart should have three columns: Key Term, Before Reading, and During Reading. Under Key Term, write each word on its own row in the chart. Record what you think each term means in the Before Reading column of the chart by either writing a statement or drawing a diagram. As you read the chapter, make notes for yourself in the During Reading column to clarify your ideas about each term.
Key Terms
Before Reading
The Chemistry of Fireworks On Canada Day, when darkness falls, the skies of towns and cities across the country come alive with colours and sounds. Flares of red, blue, green, and white are joined by cracks and bangs as fireworks displays mark Canada’s national day of celebration (Figure 4.1). Fireworks are an ancient technology, first invented in China over 2000 years ago. Today, fireworks can be seen around the world and creating them is an art form called pyrotechnics. Pyrotechnics is a branch of chemistry, the science concerned with understanding and changing matter.
The spectacular sights, sounds, and smells of fireworks come from the fusion of science and art. The designers of fireworks know that some substances burn with brilliant colours when heated (Figure 4.2). Aluminum metal is used in the kitchen as cooking foil. However, when aluminum is heated by an explosion, the metal burns with a bright white flame. To use aluminum in fireworks, it is first made into a powder so that it will burn quickly and spread out easily. The types of fireworks that light up the night sky or leave a thick glowing trail of light often contain aluminum.
Here is a summary of what you will learn in this section:
• Matter has mass and occupies volume.
• Matter is composed of particles. The arrangement and movement of the particles determines whether a substance is solid, liquid, or gas.
• Matter can be classified as a pure substance or a mixture.
• Mixtures can be further classified as mechanical mixtures, suspensions, and solutions.
Investigating Matter
4.1
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B2 Quick Lab
Observing Changes in Matter
When substances are mixed, they may change in state or they may change into different substances with different characteristics. Watch for changes in colour, volume, and state (solid, liquid, or gas) as you complete this activity.
Purpose To observe changes in matter
Procedure
1. Measure about 30 mL of bromothymol blue indicator solution into a small beaker.
2. Hold open a resealable plastic bag. Place one scoop of sodium hydrogen carbonate powder in one corner of the bag. Place one scoop of calcium chloride powder in the other corner of the bag.
3. Pour about 30 mL of bromothymol blue indicator solution into the bag. Squeeze out the air, and quickly seal the bag.
4. Mix the contents by squeezing the bag for about 20 seconds. Use your hands to detect any temperature changes.
5. Observe as many kinds of changes to the matter in the bag as you can.
6. Clean up your work area. Follow your teacher’s instructions to safely dispose of all materials used. Wash your hands thoroughly.
Questions
(a) added indicator solution to sodium hydrogen carbonate
(b) added indicator solution to calcium chloride
(c) mixed the indicator solution and both powders
8. Were there any changes to the substances in this activity? How do you know? What evidence did you observe?
• medium graduated cylinder
• calcium chloride powder
Materials & Equipment
Many substances change colour when heated. The green colours in fireworks usually come from heated copper substances, while the bright oranges are based on another substance called sodium, which is present in ordinary table salt. The crack and bang of fireworks are produced when certain substances heat up and rapidly expand. The rapid expansion makes the sound. The explosions are often so powerful that they can be felt as well as heard.
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Matter Has Many Forms Matter is anything that has mass and volume. Mass is a measure of the quantity of matter in an object. For example, a brick has more mass than an equal-sized volume of Styrofoam®. Mass is often measured in kilograms (kg) or in grams (g). Volume is a measure of how big an object is or how much space a fluid takes up. For example, a volleyball is larger than a baseball. Volume is often measured in litres (L) or in millilitres (mL). All matter has some volume, even if that volume is very small.
Matter can be solid, liquid, or gas or a combination of these states. For example, foam is a mixture of a liquid and a gas, or a solid and a gas. Bubbles in a foamy bubble bath are liquid films of soap with air trapped inside them. Styrofoam® is a solid plastic containing trapped air. Lightweight aluminum foam can be made by trapping gas inside melted aluminum and then letting the metal harden (Figure 4.3).
Changes of State Solids, liquids, and gases are called states of matter. Specific terms are used to describe changes of state of a substance (Figure 4.4). A change from a solid to a liquid is melting. A change from a liquid to a gas is evaporation (also known as vaporization). A change from a gas to a liquid is condensation and from a liquid to a solid is freezing. A solid can also change directly into a gas through sublimation. The opposite change is deposition, in which a gas changes directly into a solid.
Figure 4.3 A piece of aluminum foam
solid
sublimation
liquid
deposition
melting
freezing
evaporation
condensation
gas
Suggested Activity • B4 Quick Lab on page 146
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The temperature at which a solid turns into a liquid is called the melting point. For example, the melting point of water is 0°C. The reverse process, freezing, occurs at the freezing point. The melting point and the freezing point are always the same temperature. Similarly, the temperature at which a liquid turns to a gas is called the boiling point. The boiling point is the same temperature as the condensing point, the temperature at which a gas changes into a liquid.
The Particle Theory of Matter The particle theory of matter is a way to describe the structure of matter and its behaviour (Figure 4.5). Matter can be broken into smaller and smaller pieces. Is there a limit to how many times a piece of graphite from a pencil can be divided and still be graphite? The answer is yes. The smallest possible pieces of graphite are particles. The particle theory of matter explains how this works.
• All matter is composed of very tiny objects called particles. These particles are too small to be seen, even with a powerful light microscope.
• All particles have spaces between them. The distances between the particles change for different states of matter. For example, particles in a liquid have more space between them than the particles in a solid of the same substance, but particles in a liquid have less space between them than particles in a gas.
• Particles present in matter are always in motion. They may be vibrating back and forth, as in a solid, or moving in all directions, as in a gas. In a liquid, particles stay close together but can slide past one another.
• The particles in a substance attract each other. The amount of attraction is different for different kinds of particles. In iron, which is a very hard solid at room temperature, the particles strongly attract each other. In water, which is a liquid at room temperature, the particles of water can slide past each other because the attractions between them are not very strong.
For a given substance such as water, the state it is in is related to its temperature.
139Matter has physical and chemical properties.
solid
liquid
gas
weaker force farther apart
Figure 4.5 Particles are arranged differently in a solid, a liquid, or a gas.
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Learning Checkpoint
1. What are two features that all forms of matter have?
2. Use the particle theory of matter to explain what makes a liquid different from a solid of the same substance.
3. Compare the amount of space between particles of a gas with that of a liquid of the same substance.
4. What is the effect of adding heat to the particles in a sample of matter?
5. What is the difference between the melting of water and the melting point of water?
Figure 4.6 (a) When enough heat is added to ice, (b) the particles of water begin to slide past each other. (c) Eventually, the particles spread apart, forming a gas.
(a)
(c)
(b)
Examples Help Give a Word Meaning
Authors use examples to help readers really see the meaning of a word in their minds. If you can picture the example, you can usually understand the concept or idea. Watch for examples as you read to help you understand new terms.
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Different types and combinations of particles give every type of matter particular characteristics, or properties. A property is a characteristic that describes a substance. Substances may be classified as pure substances or mixtures, depending on how their particles are arranged.
Pure Substances A pure substance is made up of only one kind of matter and has a unique set of properties, such as colour, hardness, boiling point, and melting point. A pure substance is either an element or a compound. For example, gold is an element and sugar is a compound (Figures 4.7 and 4.8).
• An element is a substance that cannot be broken down into any simpler substance by chemical means. Later in this unit, you will learn how elements are organized into a periodic table according to their properties. Each element has its own name and symbol. For example, hydrogen’s symbol is H.
• A compound is a pure substance that is made from two or more elements that are combined together chemically. For example, water (H2O) is a compound containing the elements hydrogen and oxygen.
Figure 4.7 An ancient gold mask from Peru in South America. Gold is an element and a pure substance.
Figure 4.8 Sugar is a compound and a pure substance. All sugar particles are like all other sugar particles. It is a compound because sugar particles are made of more than one element.
Suggested Activity • B3 Inquiry Activity on page 144
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Figure 4.10 A salad vinaigrette is a mixture of oil, vinegar, and spices. When shaken, they form a suspension. After a while, the components will separate. This is why salad dressings are usually shaken before using.
Mixtures A mixture is a combination of pure substances. However, the substances in a mixture do not combine chemically as happens when a compound forms. Each substance remains in its original, pure form, although each is not always easy to see distinctly once the mixture is made. There are three main types of mixtures.
• In a mechanical mixture, the different substances that make up the mixture are visible (Figure 4.9). Soil is an example of a mechanical mixture. So is a mixture of salt and pepper. A mixture in which the different parts are visible is called heterogeneous. The prefix “hetero-” means different.
• A suspension is a cloudy mixture in which tiny particles of one substance are held within another (Figure 4.10). Tomato juice is an example of a suspension. These particles can be separated out when the mixture is poured through filter paper. A suspension is also a heterogeneous mixture.
• In a solution, the different substances that make it up are not individually visible (Figure 4.11). One substance is dissolved in another, creating a homogeneous mixture. The prefix “homo-” means same, and all parts of a homogeneous mixture look the same. Examples of solutions are sugar dissolved in hot coffee, and acetic acid dissolved in water to make vinegar.
Figure 4.9 A chocolate chip cookie is a mechanical mixture. Different parts of the mixture are visible.
Figure 4.11 Tea is a solution of water and the extract of tea leaves that are dissolved in the water. A solution is homogeneous. Every part of the tea looks like every other part.
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matter
Learning Checkpoint
1. How is a compound different from an element? Give an example of each.
2. What is the difference between a mixture and a pure substance?
3. How is a suspension different from a solution?
4. Classify each of the following as either a pure substance or a mixture.
(a) Pop is composed of water, sugar, and carbon dioxide.
(b) Carbon dioxide is composed of carbon and oxygen chemically combined.
(c) Sand is composed of white grains and black grains.
(d) The graphite at the centre of a pencil is composed of carbon.
Just like salt and other solid crystals, liquid crystals are pure substances with an ordered arrangement of matter. However, the fluidity of liquid crystals gives them some unusual properties. For example, some liquid crystals change colour with temperature changes. Find out about other properties of liquid crystals by visiting ScienceSource.
Take It Further
B3 Inquiry Activity
Changes to matter can result in the formation of gases. There are many different kinds of gas, and we can use their properties to help identify them. Three common gases are hydrogen, oxygen, and carbon dioxide.
• Oxygen gas will cause a glowing splint to reignite (catch fire).
• Carbon dioxide gas will put out a flame.
• Hydrogen gas will make a “pop” sound in the presence of a flaming splint.
Purpose To use gas tests to identify oxygen gas, carbon dioxide gas, and hydrogen gas
Procedure Part 1 — Preparation of Oxygen
1. Using a medicine dropper, add 1 mL (about 20 drops) of hydrogen peroxide solution to a clean test tube.
2. Add two drops of dish soap.
3. Using a scoopula, add a small amount (less than the size of a pea) of potassium iodide powder to the test tube.
4. Use matches to light a wooden splint.
5. Blow out the flame to make a glowing splint. Insert the glowing splint into the mouth of the test tube. Observe and record what happens to the splint.
6. Clean up as directed by your teacher.
Part 2 — Preparation of Carbon Dioxide
7. Using a medicine dropper, add 1 mL (about 20 drops) of acetic acid to the second clean test tube.
Identifying Gases
SKILLS YOU WILL USE � Conducting inquiries safely � Processing and synthesizing
data
CAUTION: Hydrogen peroxide may sting your skin. Potassium iodide will stain skin and clothing. Keep your hair tied back when working near open flames.
• 3 medicine droppers
• sodium hydrogen carbonate powder
• forceps
Skills Reference 1
Figure 4.13 A glowing splint will reignite in the presence of oxygen.
Key Activity DI
B3 Inquiry Activity (continued)
8. Using a clean scoopula, add a small amount (less than the size of a pea) of sodium hydrogen carbonate powder to the test tube.
9. Use matches to light a wooden splint.
10. Insert the flaming splint into the test tube. Observe and record what happens to the splint.
11. Clean up as directed by your teacher.
Part 3 — Preparation of Hydrogen
12. Using a medicine dropper, add about 2 mL of hydrochloric acid to the third clean test tube.
13. Use forceps to add a small piece of mossy zinc to the third test tube. Use a test tube holder to place a large test tube upside down and over the smaller test tube in order to trap any gas.
14. Keep holding the large test tube upside down as you lift it off of the small test tube. Use matches to light a wooden splint.
15. Insert the flaming splint into the large test tube. Observe and record what happens to the splint.
Analyzing and Interpreting
17. Describe what happens in a positive test for oxygen gas.
18. Describe what happens in a positive test for carbon dioxide gas.
19. Describe what happens in a positive test for hydrogen gas.
Skill Practice
20. Write a procedure for distinguishing between oxygen gas and carbon dioxide gas.
Forming Conclusions
21. Explain why the three parts of this activity can be used to distinguish among oxygen, hydrogen, and carbon dioxide gas but not to determine whether an unknown gas is one of these three.
Figure 4.14 A flaming splint will be extinguished in the presence of carbon dioxide.
Figure 4.15 Trapping hydrogen gas
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B4 Quick Lab
You can manipulate matter to change its properties. In this activity, you will mix together different liquids and a solid to produce a completely different substance: a foam.
Purpose To produce a foam and observe its characteristics
Procedure
1. Pour about 30 mL of corn syrup into a beaker. Stir in three drops of one food colouring. Use a teaspoon to sprinkle a heaping spoonful (about 20 g) of sodium hydrogen carbonate powder on the corn syrup.
2. Pour 30 mL of water into the graduated cylinder. Tip the beaker slightly, and carefully pour the water in down one side. Add 30 mL of vegetable oil to the beaker in the same way.
3. Into a separate beaker, pour 20 mL of vinegar. Add three drops of the other food colouring.
4. Fill the medicine dropper with coloured vinegar from the second beaker.
5. Position the tip of the medicine dropper at the very bottom of the first beaker, then squeeze the bulb in order to release all the vinegar. Record your observations.
Questions
7. Write a statement to describe your observations in step 4.
8. Write a statement to describe your observations in step 5.
9. What types of changes did you observe?
10. Describe a characteristic of foam that you observed.
11. Describe the state or states of matter of the foam produced in step 5.
Foam in a Cup
• corn syrup
• stirring rod
Key Concept Review 1. Water can exist as ice, liquid water, or gas.
In each of the following processes, is heat added or removed in order to change the state of water?
(a) evaporation
(b) condensation
(c) freezing
(d) melting
2. According to the particle theory of matter, gases contain particles that are far apart. Do the particles in a solid have spaces between them? Are the particles moving? Explain.
3. How could you speed up the particles that make up the silver in a table fork? How could you slow down the particles?
4. How is a mechanical mixture different from a solution?
5. The melting point of aluminum metal is 660°C. Is its freezing point slightly less than, equal to, or slightly more than 660°C?
Connect Your Understanding 6. Tin is a metal with a melting point of
232°C and a boiling point of 2602°C. What is its state of matter at each of the following temperatures?
(a) 0°C
(b) 1000°C
(c) 2000°C
(d) 4000°C
7. For each of the four statements in the particle theory of matter, choose one word that best sums up that statement’s meaning. Explain your four word choices.
8. Is a compound, such as water, a pure substance or a mixture? Explain.
9. Identify each of the following as a heterogeneous mixture, a homogeneous mixture, or a pure substance.
(a)
(b)
10. If you put olive oil in the fridge, the oil becomes solid. Explain what has happened using the particle theory of matter.
11. Can a sample of matter exist in two states at one time? Use an example to explain your answer.
12. Do all substances have the same melting point and boiling point as water? How do you know?
Reflection 13. The particles in matter are too small to see
either with the unaided eye or with a strong light microscope. Does this fact have any influence on whether you accept the statements in particle theory or not? Explain why or why not.
14. What are three things about forms of matter that you learned about in this section?
For more questions, go to ScienceSource.
4.1 CHECK and REFLECT
The Chemistry of a Campfire A fire can be fascinating to watch (Figure 4.17). Although all the flames look similar, each particular spark and flicker is unique — never to be repeated in exactly the same way. With investigation, however, some patterns become clear. Chemistry reveals that all forms of burning are variations on a theme. Every fire needs the same three components: fuel, oxygen gas, and heat.
In a campfire, the fuel is wood, a complex natural material that is rich in carbon. Carbon reacts with oxygen in the air but only if the air can reach the carbon in the wood. This is why the first step in building a campfire is usually to split a log into tiny splinters, called kindling. By chopping a thick log into kindling, much more carbon in the wood is exposed to the air. Oxygen gas has easy access to the carbon at the surface of the wood and so can react with it.
The components of a fire must be in just the right balance. When lighting a fire, extra oxygen is sometimes needed. This is why gentle blowing on the first embers of the fire can help. There is enough oxygen in the breath to provide the extra boost. It is important not to blow the heat of the first sparks away from the fuel, however, as this will blow out the fire. Because combustion releases heat, there is no need to keep relighting the flame.
Here is a summary of what you will learn in this section:
• Physical properties describe the characteristics of a substance that can be observed or measured.
• Chemical properties describe the reactivity of a substance and ways in which it forms new substances.
• Physical properties include hardness, conductivity, colour, density, melting point, solubility, and viscosity.
• Chemical properties include combustibility and reaction with water or acid.
Physical and Chemical Properties
4.2
During Reading
Understanding Vocabulary
Authors often provide additional information — called an “elaboration” — to help you understand a new term or word. As you find new terms or expressions, look not just for a definition but also for added information that clarifies the term.
Changes in Properties Fires produce new substances. One of these is invisible carbon dioxide gas. It is formed when oxygen from the air and carbon in the wood chemically combine. Where does all the wood go while it is burning? Most of the solid matter in a wood log changes into a gas and simply blows away. What is left is ash. Ash is a mixture of carbon compounds that did not have a chance to burn before the fire went out and other substances that simply do not burn. If left to burn for long enough, a fire can become smothered in its own ashes.
B5 Quick Lab
Observing a Physical Change
Soda pop contains carbon dioxide. In the air, carbon dioxide exists as a gas. However, when carbon dioxide is dissolved in water, this is not the case. The particles of water and carbon dioxide are attracted to each other, so they intermix, forming a solution. Disrupting these attractions produces a change that you will observe.
When a substance undergoes a physical change, such as melting, its appearance or state may change but its composition stays the same. For example, melted chocolate ice cream has the same composition as frozen chocolate ice cream. In contrast, a chemical change results in the formation of a new substance or substances.
Purpose To investigate a change in matter
Procedure
1. Fill the two glasses about full with soda pop.
2. Into one glass, drop a piece of the mint candy. Observe what happens in both glasses, and record your observations.
Questions
3. Adding candy to the soda pop caused a mainly physical change that disrupted the attraction between particles of liquid. How did you recognize this physical change?
4. Can you tell whether the composition of the candy changed after it was added to the soda pop? Why or why not?
5. Consider the change that took place. Suggest one reason that you would describe it as a physical change. Suggest one reason that you might also describe it as a chemical change.
6. In the procedure, you were instructed to fill two glasses with soda pop in step 1 but to add candy to only one glass. What is the reason for this?
7. Suggest ways to modify the procedure to produce an interesting effect or display involving the change in properties. Check with your teacher before trying it out.
• 2 glasses
• soda pop
Materials & Equipment
CAUTION: Do not eat or drink anything in the lab, including the soda pop and candy.
2 3
Figure 4.18 Water sticks to itself, forming droplets (cohesion), and to the spider web (adhesion).
Physical Properties of Water All life on Earth depends on water. Our bodies are about 70 percent water. Some plants are 95 percent water. A characteristic of water is that it sticks to itself, a property that is known as cohesion. Due to cohesion, water forms beads on non-absorbent surfaces, such as glass. Water also sticks to other substances, a property known as adhesion (Figure 4.18). Adhesion allows you to mop up water with a towel.
A physical property describes a characteristic of a substance that can be observed or measured. One example of a physical
property is the melting point of a substance. Water has many interesting physical properties that make it very useful to organisms. For example, adhesion and cohesion help move water up through the stems of plants, including tall trees. Its ability to be a liquid at room temperature is another.
Most materials shrink when they freeze. Water does not. Due to special interactions between water particles during freezing, water actually expands. This makes ice less dense than liquid water. As a result, ice
floats on water. Why is this important? In winter, the ice on a body of water shelters the fish below. Floating ice can also make a useful temporary roadway or platform for ice fishing (Figure 4.19). However, the same properties that make water useful can also cause problems. As ice forms, it widens cracks in roads. In addition, snow and ice on the roofs of houses can cause damage when it melts and refreezes. Not only is the ice heavy, it can block gutters and downspouts that are meant to keep water flowing off the roof and away from the sides of the building.
Observing Physical Properties Figure 4.20 shows a dull, red, clouded piece of beach glass. Three physical properties of the glass include its lustre (shiny or dull), its colour, and its transparency (how see-through it is). Other physical properties can be observed using special equipment. For example, you could measure the mass and the volume of the glass to determine its density. Table 4.1 lists a number of other physical properties.
Figure 4.19 In winter, fish are protected from freezing temperatures by the ice at the surface of the water. People can use this same ice as a platform when fishing.
Figure 4.20 The pieces of beach glass show a variety of physical properties.
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Property Description Examples What It Looks Like
Colour and lustre The light a substance reflects gives it colour and lustre (shine).
The names for some substances, such as gold, are also the names of colours. Gold has lustre; concrete is dull.
Conductivity Conductivity is the ability of a substance to conduct electricity or heat. A substance that conducts electricity or heat is called a conductor. A substance with little or no conductivity is an insulator.
Most metals are good conductors. Copper is a very good conductor of electricity and so is used to make electric wires. Styrofoam® and glass are insulators.
Density Density is the amount of mass in a given volume of a substance.
The density of pure water is 1 g/mL. The density of gold is 19 g/mL. Water is denser than oil, but gold is denser than water.
Ductility Any solid that can be stretched into a long wire is said to be ductile.
Copper is a common example of a ductile material.
Hardness Hardness is a substance’s ability to resist being scratched. Hardness is usually measured on the Mohs hardness scale from 1 to 10.
The mineral talc is the softest substance on the Mohs hardness scale (1). Emerald is quite hard (7.5). Diamond is the hardest (10).
Malleability A substance that can be pounded or rolled into sheets is said to be malleable.
Aluminum foil is an example of a malleable substance. Metals such as gold and tin are also malleable.
Viscosity Viscosity is the resistance of a fluid to flow.
Syrup has a high viscosity compared to water.
Gold and silver coins
Fluids and solids with different densities
Copper wire
Observing Chemical Properties A chemical property describes the ability of a substance to change into a new substance or substances. Chemical properties include how a substance interacts with other substances, such as acids, or how it reacts to heat or light. A chemical change always results in the formation of a new substance or substances. For example, when zinc metal and hydrochloric acid are mixed, they undergo a chemical change that produces two new substances: hydrogen gas and a compound called zinc chloride. A chemical reaction is a process in which a chemical change occurs.
Chemical properties can be observed only when a chemical change occurs. If you mix baking soda and vinegar, you will produce a chemical change that involves the formation of gas bubbles. In general, evidence of chemical change can include a great variety of changes, including colour, odour, temperature, the production of light, the formation of a new solid inside a liquid, or the production of a new gas (Figures 4.21 and 4.22). Table 4.2 lists various chemical properties.
Figure 4.22 Chemical changes made this banana ripe — and then rotten.
Figure 4.21 Fireflies contain a chemical called luciferin. When luciferin reacts with oxygen, light is emitted.
Suggested Activities • B7 Inquiry Activity on page 156 B8 Inquiry Activity on page 158 B9 Design a Lab on page 160
Chemical Properties
Table 4.2 Examples of Chemical Properties
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chemicals that will react with water
Heat and Chemical Change Applying heat to a substance can result in chemical changes. For example, when baking powder is heated, it undergoes a chemical change that results in the production of carbon dioxide gas. This is very useful in cooking. It is this chemical reaction of baking powder in some baked foods that produces the gas needed to lift the cake and make it light and fluffy (Figure 4.23). If you forget to add baking powder to a cake batter, the cake will be flat and dense.
Heating causes many different kinds of substances to react. Burning is another example of this kind of chemical change. Paper is combustible and so will simply burst into flame when raised above a certain temperature. Combustibility is the ability of a substance to react quickly with oxygen to produce heat and light.
When some substances are mixed, their reaction absorbs heat. A chemical cold pack, for example, depends on a reaction that absorbs heat (Figure 4.24). Typically, a chemical cold pack is filled with water but also has an inner bag or tube full of chemicals. The inner compartment keeps its contents separated from the water until it is time to use the cold pack. When the inner bag is popped open, the chemicals within mix with the water in the cold pack. The reaction removes heat from the surroundings, and so the pack feels cold to the touch.
Figure 4.23 When baking powder in a cake batter is heated, it produces a new substance: a gas.
Learning Checkpoint
2. List three physical properties of water.
3. What is a chemical property?
4. List three examples of chemical properties.
5. How does a physical change differ from a chemical change?
Figure 4.24 A chemical cold pack has an inner compartment containing reactive chemicals and an outer compartment containing water.
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Controlling Changes in Matter to Meet Human Needs In our everyday lives, there are many examples of how understanding and controlling changes in matter help us meet our basic needs. Consider the freeze-dried foods business. Freeze- drying is a way to preserve foods so that they can be eaten months and sometimes years later. As well, freeze-drying makes foods easy to prepare: all you have to do is add hot water (Figure 4.25).
In the freeze-drying process, the food is first frozen to convert the water content in the food to ice. The frozen food is then put in a pressure chamber, and the pressure is reduced until the ice sublimes (changes from a solid to a gas). The result is that about 98 percent of the water in the original food item is removed. This leaves a food that is about 10 percent its original mass and that, once packaged, does not need to be refrigerated. Freeze-drying is also used by biologists to study tissue samples and by restoration experts to rescue important documents that are water damaged.
During hot, dry weather, hikers are often restricted from making campfires. However, a fire-free heating pouch has been developed. The freeze-dried food is placed in the heating pouch. The pouch contains the elements magnesium and iron, as well as salt, which is a compound. When water is added to these chemicals, the resulting chemical change releases enough heat to warm the freeze-dried contents.
Figure 4.25 Freeze-drying removes the water from food, which preserves the food until it is time to eat.
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Adding cornstarch to plastic is one way to make the plastic biodegradable. Find out about other “green” products by visiting ScienceSource.
Take It FurtherFrom Corn to Biodegradable Plastic Wrap Being able to change materials from one form to another allows us to make products that are not only useful but which also support a sustainable environment. For example, chemicals made from corn can be used to make juice bottles, remove paint or nail polish, and fuel some cars. Corn is put through a chemical change called fermentation. Once this chemical process is complete, the new substances are recovered, purified, and made into solvents, biodegradable plastics, and automobile fuel.
Solvents are substances that dissolve other substances. Solvents are useful for making inks and nail polish and for removing paint. Corn-based solvents are not as harmful to the environment as some other types of solvents (Figure 4.26). An advantage of corn-based biodegradable plastics is that they can be broken down by bacteria. However, making and using corn-based products also has its drawbacks. People sometimes cut down rainforests to make way for cornfields. Corn that would otherwise be used for food is sometimes diverted to make disposable products.
B6
Polyethylene Plastic
Polyethylene plastic is flexible, heat resistant, and strong. Children play with polyethylene toys, athletes drink from polyethylene bottles, and police officers wear polyethylene vests. Unlike some other types of plastic, polyethylene is considered safe to use in food containers.
What happens to polyethylene products when we no longer need them? If they cannot be reused, another option is to recycle them. Some types of polyethylene break down more easily when exposed to sunlight. These types of plastics are considered photodegradable. This process releases tiny pieces of polyethylene.
1. Make a list of items you used today that are made from polyethylene. Identify which items you could live without and which are necessities.
2. Describe two ways you could help decrease the amount of polyethylene that goes into landfills.
3. What are some possible benefits of using photodegradable polyethylene to make disposable food containers or shopping bags? What are some possible problems with this type of plastic?
Science, Technology, Society, and the EnvironmentSTSE
Figure 4.26 The inks used here contain solvents made from corn.
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B7 Inquiry Activity
Question How can you identify a substance from its properties?
Procedure
1. In your notebook, make an observation table like the one below.
2. Read the labels of the six known white substances, and note any hazard symbols or cautions.
Part 1 — Appearance
3. Place the spot plate on a piece of paper. Label the top of the spot plate with the tests you will conduct.
4. Label the left of the spot plate with the identity of two or more of the six known white substances. Using a clean scoopula each time, deposit a sample of each substance in a separate well in the first column of the spot plate.
Using Properties to Identify Pure Substances
SKILLS YOU WILL USE � Observing and recording
observations � Using appropriate formats to
communicate results
Substance Appearance Crystal Shape Water Acid Iodine
Cornstarch
CAUTION: Iodine will stain your skin and clothing.
Figure 4.27 Placing substances in the spot plate
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5. Closely observe each white substance. In your table, record as many observations as you can about the appearance of each substance.
Part 2 — Shape
6. Use the magnifying lens to observe the crystal shape of each white substance. Record the crystal shape of each substance as “regular” or “irregular.”
Part 3 — Water
7. Use a clean scoopula to place a bit of the first substance into three more wells in the same row. Do the same for the second substance.
8. Using a medicine dropper, add a few drops of water to the second well of the second and third rows. Record your observations.
Part 4 — Acid
9. Using a clean medicine dropper, add a few drops of hydrochloric acid to the third well of the second and third rows. Record your observations.
Part 5 — Iodine
10. Using a clean medicine dropper, add a few drops of iodine to the fourth well of the first and second rows. Record your observations.
11. Clean out the spot plate as directed by your teacher.
12. Repeat steps 3–11 for the remaining white substances.
Part 6 — Unknown Substance
13. Repeat steps 3–11 for an unknown substance provided by your teacher. Be sure to record the unknown substance number in the table.
15. For each white substance, there is one unique property that distinguishes it from the others. Identify this property for each white substance.
16. Which results from this inquiry were not what you expected? Explain.
17. How can the properties of the six white substances be used to identify the unknown substance?
18. What is the identity of the unknown substance? Explain how your observations support your conclusion.
Skill Practice
19. Identify the chemical and physical properties you observed in this activity.
Forming Conclusions
20. Write concluding statements to describe the chemical and physical properties of each substance that you examined.
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B8 Inquiry Activity
You can use a chemical reaction to change one substance into another substance that has different physical and chemical properties. You can also use heat to change the properties of substances.
Question What are some characteristics of physical changes and chemical changes?
Procedure 1. Copy the following observation table into your
notebook. Be sure to leave a row for each test.
Test 1 — Sodium carbonate and hydrochloric acid
2. Using a scoopula, add a small amount (the size of a pea) of sodium carbonate powder to the beaker. In your observation table, describe the appearance of the sodium carbonate powder.
3. Using a clean medicine dropper, obtain a few drops of hydrochloric acid. Observe the hydrochloric acid, and record what you see in your observation table.
4. Write a statement about the kinds of evidence for physical or chemical change that you will look for when you add the hydrochloric acid to the sodium carbonate.
5. Add five to eight drops of hydrochloric acid to the sodium carbonate. Record your observations.
Test 2 — Sugar and heat
6. Obtain an aluminum muffin tin. Use a clean scoopula to put a small amount of sugar (the size of a pea) in the centre of the aluminum muffin tin. Record your observations of the sugar.
7. Suggest possible ways that the sugar might change with heating.
8. Place the candle securely in a candle holder, then light the candle.
9. Using tongs or a wooden clothespin, hold the aluminum muffin tin over the candle’s flame. Slowly move the muffin tin back and forth over the flame to heat the sugar. Record your observations.
10. Place the aluminum muffin tin in a safe place to cool.
Investigating Physical and Chemical Changes
SKILLS YOU WILL USE ■ Observing and recording
observations ■ Justifying conclusions
CAUTION: Copper(II) sulphate is poisonous and can stain your clothes and skin. Keep your hair tied back when working near open flames.
Skills References 1, 2
• two 5-mL measuring spoons
Sodium carbonate and hydrochloric acid
Table 4.4 Observations of Physical and Chemical Changes
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Test 3 — Copper(II) sulphate and sodium carbonate
11. Using a measuring spoon, add 5 mL of copper(II) sulphate solution to a clean test tube. Using a different measuring spoon, add 5 mL of sodium carbonate solution to another test tube. In your observation table, describe the appearance of each solution.
12. Write a suggestion about what you think will happen when the solutions are combined.
13. Combine the solutions, and record your observations.
14. Dispose of the solutions as directed by your teacher.
Test 4 — Copper(II) sulphate and water
15. Using a scoopula, add a small amount (the size of a pea) of solid copper(II) sulphate to a clean test tube. In your observation table, describe the appearance of the substance.
16. Write a suggestion about what you think will happen when you add water to the copper(II) sulphate.
17. Fill the test tube full of water and record your observations. Use a stirring rod to mix the water and copper(II) sulphate, and record any additional observations.
19. Which of the changes that you observed were physical? How do you know?
20. Which of the changes that you observed were chemical? How do you know?
Skill Practice
(a) sodium carbonate
Forming Conclusions
22. Create a flowchart that a classmate could follow in order to identify physical and chemical changes.
2 3
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B9 Design a Lab
Elements, compounds, and mixtures are part of everyday life. From the kitchen to the chemistry lab, we make use of different substances for their different properties.
Question How can you use chemical and physical properties to distinguish among common substances?
Design and Conduct Your Investigation
1. Choose at least three substances to investigate. They may be substances from your chemistry lab or from home.
2. Decide which properties you will investigate. Select some from the list below, or add others.
• colour and lustre
• reaction with acid
• reaction with water
3. Have your teacher approve your list of test substances and the properties you wish to investigate.
4. Plan your procedure. Think about these questions:
(a) How will you observe different properties, and what materials and equipment will you need to make these observations?
(b) How will you record your results?
(c) How will you organize and present your results?
5. Write up your procedure. Show it to your teacher for approval before carrying it out.
6. Carry out your procedure, and collect your observations.
7. Present your findings in a poster or in another form suggested by your teacher.
Properties of Common Substances
materials � Observing and recording
Figure 4.30 Possible materials and equipment
CAUTION: Keep your hair tied back when working near open flames. Take note of safety precautions for the substances you will be working with.
Skills References 1, 2
about a substance?
2. For each of the following substances, list four physical properties.
(a) water
3. What does a chemical property describe about a substance?
4. Identify each of the following observations as evidence of either a physical change or a chemical change.
(a) A piece of copper is heated until it melts.
(b) A piece of aluminum corrodes in a solution of acid.
(c) A piece of paper burns in a candle flame.
(d) A piece of plastic is stretched until it breaks.
(e) Table salt boils at 1465°C.
5. From the following list, indicate which items would make good conductors.
(a) copper
(b) Styrofoam®
(c) iron
(d) woollen mitten
6. What is the difference between the properties of ductility and malleability?
Connect Your Understanding 7. Would you rather mop up spilled milk with
a paper towel or a plastic bag? Use the terms “adhesion” and “cohesion” to explain your choice.
8. Identify each of the following as a statement that describes either a physical property or a physical change.
(a) Ice melts.
(c) You chop a carrot.
(d) A diamond jewel is hard.
(e) Copper wire bends easily.
(f) The ruby slippers are red.
9. Examine this photograph of the graduated cylinder. What properties of water allow it to form a meniscus (the curve in the water)?
10. Use diagrams and captions to explain what happens to the particles of matter in each of the following situations.
(a) Butter melts.
(c) Water vapour in the air cools and forms raindrops.
11. Do water and vegetable oil have the same freezing point? How do you know for sure?
Reflection 12. Name an object that you use every day,
such as earphones, a plastic mug, or your toothbrush. What would you like to find out about this object’s properties now that you have completed this section?
For more questions, go to ScienceSource.
Question 9
For Dr. Lee Wilson, chemistry is not just a research subject — it is a source of solutions to problems that touch our lives. Dr. Wilson is an award- winning professor of chemistry at the University of Saskatchewan, where he teaches and conducts research (Figure 4.31). He hopes his work will made a big difference in medical and environmental science.
Dr. Wilson’s special interest is in nanostructured materials. Nanostructured materials are made from components too small to be seen even with a light microscope. These components, which are less than 0.0001 mm in size, are very useful for making membranes with tiny pores. Such membranes can be used as filters to purify water of toxic chemicals.
The opaque white material looks very ordinary, despite its special properties. Dr. Wilson says that the material acts like a sponge. Instead of trapping water, however, the material traps small particles, such as contaminants.
Personal experience has been a major motivating factor in Dr. Wilson’s work. While working in rural Alberta, his father became dangerously ill due to contaminated water and had to have surgery. Dr. Wilson would like to see his research used so that even remote communities can protect their water supplies.
Figure 4.31 Dr. Lee Wilson wants his research to make a difference in the world.
Dr. Wilson feels it is important to be a scientist with a conscience. Scientists should do work that benefits society as a whole, he says.
He also says it is important to follow your passion. “When I have a passion for something, whether it be a problem to solve or an idea of interest, it is the passion that carries me through the hardship, despite how difficult the challenges in solving the problem or learning a new skill may be.” Dr. Wilson was the first in a small Metis community in Manitoba to go to university, the first in his family to complete a university degree, and the first Metis student to get a PhD from the University of Saskatchewan.
Today he mentors young Aboriginal students participating in science fairs and camps and his own graduate students (Figure 4.32). His advice to young scientists is to get a good education, take lots of science courses, but also to take courses in the arts. Scientists need to be able to communicate, he says, not just do research in a lab.
Questions
1. How is Dr. Lee Wilson’s work being applied to improve the environment?
2. ScienceSource Use the Internet to research nanostructured materials. What are nanostructured materials, and how are they different from other substances?
CAREERS in ScienceInvestigating
Figure 4.32 Dr. Lee Wilson working with his students
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Lost Wax — Found Metals
Imagine sculpting a beautiful object or statue in clay and then transforming it into a single solid piece of metal. This is the job of a foundry artisan. A foundry artisan is a master of both the art and science of manipulating matter. A foundry is a place where metals such as gold and iron are fashioned into specialized parts. The metal is first melted until it becomes a liquid and then poured into a mould where it can harden and take on a new shape. An artisan adds creativity to the process, often making one-of-a-kind pieces of art.
It may take an artist a week or a month to make a clay sculpture. When it is ready, the sculpture is brought to a foundry, where the work is completed. The clay sculpture is covered with silicone rubber to form a mould. The mould is a “negative” version of the clay sculpture. Hot wax is poured into the mould to coat the inside. This step is repeated until a “positive” version of the clay sculpture has been created. This looks just like the original clay sculpture. A second negative of the sculpture is made by coating the wax with a ceramic material, which is a solid that can withstand the heat of molten metal without
breaking. Melting away the wax creates an empty vessel into which molten metal can be poured.
One major step remains before the cast metal piece of art is complete. A hot furnace is used to heat aluminum, silver, iron, or gold until it melts. The metal is then poured into the empty mould, where it takes on the shape of the original clay sculpture (Figure 4.33). After allowing the mould to cool slowly, it is removed and the metal piece is sanded and polished to add the finishing touches. The cast metal art is now ready for sale or shipping to the museum or person who commissioned it (Figure 4.34).
The work of a foundry artisan takes a combination of skills and talents. Being able to visualize the finished product from the start is important. A foundry artisan is creative, pays attention to detail, and has the self-discipline to meet deadlines. Also, an artisan must know how to work safely in the foundry.
Most artisans apprentice with an expert in order to learn the specific skills they need for foundry work. Many have been to art college or studied the arts in university. It is common for artisans to be self-employed, and so basic business training can be helpful.
Questions
1. The process of casting a piece of artwork in metal involves making several positive and negative versions of the final cast object. Sketch a flow chart that identifies these steps.
2. ScienceSource Research where you can take courses in jewellery casting or foundry art.
Figure 4.33 Foundry artisans working with hot liquid metal
Science in My FUTURE The Art of Chemistry
Figure 4.34 The final product
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Key Concept Review 1. What is the main difference between a pure
substance and a mixture? Name an example of each.
2. What is a chemical change?
3. In the following diagram, what change of state does each letter indicate?
4. Low-density polyethylene is a plastic that can be stretched somewhat without breaking it. Why is this property useful for disposable shopping bags?
5. Explain the difference between cohesion and adhesion, using an example.
6. Explain why particles of water in the air can form frost on a cold window.
7. Name a physical property that is:
(a) shared by gold, copper, and iron
(b) shared by gold and copper but not iron
(c) shared by diamond and glass
(d) not shared by diamond and glass
8. What are two physical changes that cooling a hot substance may result in?
9. For each example, identify whether the property described is chemical or physical. Justify your answer in each case.
(a) Bronze metal has a shiny lustre.
(b) When silver nitrate is added to calcium chloride, a cloudy solid (precipitate) appears.
(c) Mercury is liquid at room temperature.
Connect Your Understanding 10. Identify the processes shown in the
following photographs as chemical changes or physical changes. Justify your answers.
(a)
(b)
(c)
t
c
k
k
k
c
k
k
k
k
Communication Applicationac
12. Classify and compare the following mixtures.
(a) a drink made by dissolving drink crystals in water
(b) a cup of tea with tea leaves in it
(c) tomato juice
13. How can the application of heat result in a chemical change? Explain, using an example.
14. Metal foams are 75 to 95 percent air. What effect does this have on the density of metal foam compared to solid metal?
15. If water freezes inside of a building’s water pipes, the pipes may burst. Explain why this happens.
16. Some types of clear plastic can be used to make lenses. List three important properties of plastic that make it suitable for use in eyeglass lenses.
17. Winter car tires are made from a soft type of rubber that remains flexible, even in icy temperatures. Winter tires also have deeper grooves than all-season tires. Do you think people should be required by law to have winter tires for their vehicles? Why or why not? Support your response with a discussion of the properties of rubber tires.
18. List five items you have used today. Try to identify one substance that each item is made from and the property or properties that make that substance useful. For example:
cellphone — plastic — lightweight and hard
19. Maple syrup comes from the sap that flows in maple trees. The sap is collected and then boiled so that much of the water it contains
will evaporate. Boiling off the water increases the sugar concentration of the syrup and makes the syrup more viscous. Describe what is happening to the particles in the syrup at each stage in the process.
20. Consider a homogeneous mixture, such as a salt solution, and a heterogeneous mixture, such as rice and pebbles. Suggest and compare how you could separate the substances within each type of mixture.
Reflection 21. Describe something that you did not know
before reading this chapter about how people change the properties of matter.
22. How has your opinion of the use of chemicals in our society changed since completing this chapter? c
c
a
c
a
c
a
a
t
a
a
a
Reflect and Evaluate
Review the “Language of Chemistry” chart you made at the beginning of the chapter. How did the strategies for finding word meanings help you to add definitions and explanations of new terms in the “During Reading” section of the chart? Compare your chart and use of strategies with a partner, and discuss how each strategy helped you to get a clear picture of new vocabulary.
After Reading
Unit Task Link
What steps should you take before investigating the properties of different substances? List some of the physical and chemical properties that you could investigate in the Unit Task, for which you will design a toothpaste. Make a list of safety precautions that you and your lab partners will need to follow.
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Name ___________________________ Date: __________________ Class:_____
( PHYSICAL PROPERTY CHEMICAL PROPERTY 1. observed with senses 1. indicates how a substance 2. determined without chang ing reacts with something else the composition of the matter 2. matter will be changed into a new substance after the reaction )Section 4.2 p. 148-155
PHYSICAL AND CHEMICAL PROPERTIES AND CHANGES PRACTICE
Identify the following as a chemical (C) or physical property (P):
______1. blue color ______8. melting point
______2. density ______9. reacts with water
______3. flammability (burns) ______10. hardness
______4. solubility (dissolves) ______11. boiling point
______5. reacts with acid ______12. luster
______6. supports combustion ______13. odor
______7. sour taste ______14. reacts with air
( PHYSICAL CHANGE CHEMICAL CHANGE 1. a change in size, shape, or state 1. a change in the physical and 2. no new substance is formed chemical properties 2. a new substance is formed )Identify the following as physical (P) or chemical (C) changes.
_____1. NaCl (Table Salt) dissolves in water. ______9. Milk sours.
_____2. Ag (Silver) tarnishes. ______10. Sugar dissolves in water.
_____3. An apple is cut. ______11. Wood rots.
_____4. Heat changes H2O to steam. ______12. Pancakes cook.
_____5. Baking soda reacts to vinger. ______13. Grass grows.
_____6. Fe (Iron) rusts. ______14. A tire is inflated.
_____7. Alcohol evaporates . ______15. Food is digested.
_____8. Ice melts. ______16. Paper towel absorbs water.
Physical and Chemical Changes
Can you recognize the chemical and physical changes that happen all around us? If you change the way something looks, but haven’t made a new substance, a physical change (P) has occurred. If the substance has been changes into another substance, a chemical change (C) has occurred.
1.
An ice cube is placed in the sun. Later there is a puddle of water. Later still the puddle is gone.
2.
Two chemical are mixed together and a gas is produce.
3.
4.
5.
6.
7.
9.
10.
Section 4.2 p. 148-155
[1] Describe the difference between chemical and physical changes.
______________________________________________________________________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________________________________________________________________
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
Read each scenario. Decide whether a physical or chemical change has occurred and give evidence for your decision. The first one has been done for you to use as an example.
Scenario
Evidence…
1.
A student removes a loaf of bread hot from the oven. The student cuts a slice off the loaf and spreads butter on it.
Physical
No unexpected color change, temperature change, or gas given off.
2.
Your friend decides to toast a piece of bread, but leaves it in the toaster too long. The bread is black and the kitchen is full of smoke.
3.
You forgot to dry the bread knife when you washed it and reddish brown spots appeared on it.
4.
5.
In baking biscuits, the baking powder reacts to release carbon dioxide bubbles. The carbon dioxide bubbles cause the dough to rise.
6.
Chewing food to break it down into smaller particles represents a _________ change, but the changing of starch into sugars by enzymes in the digestive system represents a ___________change.
7.
A piece of wire is coiled to form a spring.
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chapter 4 section 4.2 : physical & chemical properties ...nov 04, 2018 · plastic, diamond, road...

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