matter and energy. density 1. density: the amount of matter packed into a volume. 2. equation: 3....

Matter And Energy

Density

1. Density: the amount of matter packed into a volume.

2. Equation:

3. Units for density include:A. g/mL

B. g/cm3

V

md

volume

mass

md v

liquid mercury

brass nutwater

cork

4. Sample problemsA. Find the density of an object in g/cm3 if the

mass is 4.370 g and the volume is 2.12 cm3.

m =

v =

D =

B. A cube of metal has a density of 4.51 g/cm3. If 95.7 grams of the metal is added to 145 mL of water in a graduated cylinder, to what volume would the water rise?

m =

v =

D =

Hmm tricky

C. A cube of metal has a density of 0.997 g/mL and volume of 3019 mL. What is the mass of the cube?

m =

v =

D =

D. An aluminum block has the mass of 57 grams. The volume of the block .0211 L. What is the density of the aluminum block?

What’s the plan?

Convert the .0211 L to mL and then solve the problem by dividing 57/21.1

3

base K H D da c m

1 2

You move 3 spaces to the right

i. 0.0211 L = 21.1 mL

m =

v =

D =

E. You enter a pawn shop looking to purchase a gold coin. The shop keeper shows you an amazing looking coin, but you are not sure if it’s 100% gold or not. You purchase the coin for a high price anyway, and test the coin to see if it’s pure gold. Wikipedia says that the density of gold is 19.32 g/cm3.

You bring your coin to chemistry class to conduct an experiment. You fill a large graduated cylinder up to 30.0 mL and carefully drop the coin in. The water rises to 35.6 mL. You place the coin on a balance and find it to be 35.4 grams. What is the density of the gold coin? Should you be happy with your purchase or go back to complain?

m =

v =

D =

Matter

1. Matter: anything that takes up space, has mass, and shows inertia.

A. Inertia: resistance for any object to change its state of motion.

Also referred to as Newton’s First Law of Gravity.

2. The basic piece of matter is the atom.

3. The atom can be broken down into smaller parts called subatomic particles.

A. Subatomic particles include: protons, neutrons, and electrons.

B. Proton: positively (+) charged subatomic particle.

C. Electron: negatively (-) charged subatomic particle.

D. Neutron: Neutral charged subatomic particle.

E. Nucleus: center of atom made of protons and neutrons.

4. When two or more atoms form a bond, then a molecule is formed.

2. Nucleus

1. Atom

Electron

Proton

Neutron

Water

Methane

Phosphatidylinositol

Phases and Phase Changes

1. Three widely known phases: solid, liquid, gas.

Important to know what the molecules are like in each phase

A. Solid: molecules are packed tightly together, but can still vibrate.

B. Liquid: molecules can move around, but are still close to each other.

C. Gas: molecules can move around freely, and are not close to each other.

(a) Solid (b) Liquid (c) Gas

2. Plasma: state of matter where electrons are stripped from atoms. Occurs at high temperatures.

A. Ex: florescent light, flame, lightning, sun.

Plasma TV’s?

Made of millions of tiny “cells” or “florescent lamps.”

Pure Substances

1. Made up of only one material.

2. The material can be an element or a compound.

A. If it is an element, then it’s found on the periodic table.

B. An element is a pure substance made of only one kind of atom.

3. Diatomic Gases: gases that are always found in pairs.

A. Include: H2, N2, O2, F2, Cl2, Br2, I2

4. Allotropes: different forms of the same element.

A. Example: diamonds and graphite.

Diamond Inclusions

5. Compounds: form when two different elements join chemically.

A. When a chemical reaction occurs, both physical and chemical properties are highly likely to change.

Mixtures: homogeneous and heterogeneous mixtures

1. A mixture is a physical combination of two substances.

2. The different parts can be separated physically using various methods.

3. No new substances should be occurring.

4. Heterogeneous mixture: a mixture that is not equally mixed.

A. Different regions have different physical properties.

B. Ex: Italian dressing, pepperoni pizza, chocolate chip cookies.

5. Homogeneous mixture: mixture that has particles evenly mixed.

A. All phases of matter (solid, liquid, and gas) can be in a homogeneous mixture.

B. Ex: air, gasoline, 14-karat gold

C. Homogeneous metals are called alloys.

D. Homogeneous liquids are called solutions.

E. Solutions cannot be separated through a filter.

Carat measures two things: mass and purity.

Carats for rings are based on 24-carat scale.

24 carat is pure gold.

14 carat-gold rings would have slightly more than half gold. 10 carat rings would be slightly less than half gold.

Brass is not a pure metal. It’s a homogeneous mixture of copper and zinc.

Compound or Element

Compound or Element and Pure Substance or Mixture

Mixtures Vs. Compounds

1. Mixtures are physical combinations. Compounds are chemical combinations.

2. Compounds change properties, while mixtures have a combined property.

Ex: Alloys are normally stronger (Steel made of iron and carbon). Methanethiol (mercaptan) gas added to natural gas. Methanethiol still smells.

3. Atoms in compounds always combine in whole numbers. No fractions or decimals.

A. Ex: H2O. CO2 . You never see H3.5O or CO9.2

4. To separate a compound back into its pure substances, then you must use other chemical reactions.

5. Mixtures can be separated using physical methods.

Physical Vs. Chemical Property

1. Chemists - and you - will study physical and chemical properties.

In order to study both you must be able to determine the difference.

2. Physical property: observations made without changing the composition or identity of a substance.

A. Ex: ice is made of what molecule? _______

B. Ice will melt at what temp? ___________

C. What is the molecule after when ice melts to water? _____________

Think of your own example of a physical property.

H2O

0ºC or 32ºF

H2O

3. Physical properties can be categorized as either extensive or intensive.

A. Extensive physical properties: a property where the amount of matter is important.

i. Example: mass, volume, length, and size.

B. Intensive physical properties: a property where the amount of matter is not important.

i. Example: color, density, melting point, boiling point.

C. When remembering extensive and intensive properties think of cutting a substance in half. If you are asked if color is an extensive or intensive property how could you tell? You must remember that extensive properties depend on the amount of matter present. Then ask yourself, if you have a red ball, and you cut the ball in half, will the color of the two halves be the same? Yes. Intensive property. How about mass? If you have a red ball and you cut it in half, will the halves have the same mass? No – so mass is an extensive property.

4. Chemical properties: how a substance reacts with another substance.

A. When atoms and molecules react with each other to form new molecules, physical properties often change.

5. Chemical reactions can be used to change one substance into another.

This does not mean that you can take lead and turn it into gold. That takes a nuclear reaction.

6. Chemical reactions have two sides

A. The left side of the arrow (with the N2 + H2) is called the reactant side.

B. The right side of the arrow (with the NH3) is called the product side.

C. The entire reaction is called a chemical equation.

N2 + H2 NH3

7. What does the chemical equation tell us?A. What you start with what you end with

Classify the following as either a chemical or physical property:

1. Color

2. Flammability

3. Hardness

4. Odor

5. Taste

Physical Change vs. Chemical Change

1. A physical change happens when you do a reaction, but no new substance occurs.

2. A chemical change happens when you do a reaction, and a new substance does occur.

A. When a new substance is formed it is hard, unless you use a lot of energy, to go back to the original substance.

B. Example: You have a log burning outside, it releases gas and you are left with a pile of ash. It would be impossible to remake that log because you would need to trap all the gas being released.

C. Signs of a chemical reaction include: i. Bubbling

ii. temperature and/or color changes

iii. formation of a solid when mixing two liquids.

iv. Odor released

Classify the following as either a chemical or physical change:

1. Boiling water becomes steam

2. Butter turns rancid

3. Burning of wood

4. Mountain snow melting in spring

5. Decay of leaves in winter

Energy

1. Energy: a quantity used to show the amount of work done.

2. Different forms of energyA. Kinetic energy: the energy of motion.

i. Equation for kinetic energy = ½ mv2 .

ii. m = mass

iii. v = velocity

Also defined as a work needed to move an object of some mass to a specific speed.

B. Potential energy: stored energy

i. Examples: stretched rubber band, rollercoaster at the top of a hill, and a battery.

2. Energy can also be transformed.A. Different types of energy include: mechanical,

thermal, and chemical.

Ex: mechanical E is associated with motion or position of an object

Ex: Thermal E is the movement of heat from warmer to cooler objects.

Ex: chemical E is the breaking and reforming of chemical bonds.

3. Conservation of Energy: states that energy is never created nor destroyed. Energy is always transformed.

4. In a chemical reaction, if energy in the form of heat is given off, the reaction is exothermic.

A. Example equation

Fe2O3(s) + 2Al(s) Al2O3(s) + 2Fe(l) + energy

B. Example of exothermic reactions: wood burning or fireworks exploding.

Must have a chemical change occurring!

5. In a chemical reaction, if energy is absorbed, then it is considered endothermic.

A. After a reaction if the substance feels cold, then it’s most likely endothermic.

B. Example equation:

Ba(NO3)3∙8H2O + 2NH4SCN + heat Ba(SCN)2 +

NH3 +10H2O

C. A substance can also get warmer, too (quite confusing).

D. Ex: Ice + heat water. This is an endothermic reaction. Water + heat steam.