the science of chemistry
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The Science of Chemistry. Chapter 1 Chemistry I 5.0. Alchemy. How do you picture a chemist?. What is chemistry?. Chemistry is the study of all things and the changes they can undergo. Chemistry is called a central science because it overlaps so many sciences. - PowerPoint PPT PresentationTRANSCRIPT
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The Science of Chemistry
Chapter 1
Chemistry I 5.0
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Alchemy
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How do you picture a chemist?
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What is chemistry?
l Chemistry is the study of all things and the changes they can undergo.
l Chemistry is called a central science because it overlaps so many sciences.
l Chemical – is any substance with a definite composition.
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What is chemistry?
l Changes in chemicals (A.K.A.) chemical changes
l The process in which one or more substances change to produce one or more different substances.
l Matter – The stuff in which everything is made up of. Matter can be defined as anything with mass and volume.
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States of Matter
State Shape Volume Movement Structure
Solid
Liquid
Gas
Definite Definite
DefiniteIndefinite
Indefinite Indefinite
Vibrate Slightly
Move More
Move the fastest
Most Rigid
Less Rigid
Least Rigid
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States of Matter
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States of Matter
melting
freez
ing
condensing
evaporating
depositionsublimation
Solid
Liquid Gas
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Physical Changes
l Do NOT change the identity
l Often change what the substance looks like
l Examples: mixing ice tea in water, crushing a rock, freezing water
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Chemical Changes
l Alter the identity of the substance.
l The new substance has a different composition than the beginning substances.
l Examples: rusting and burning
l A shorthand way to express a chemical reaction is with a chemical equation.
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Chemical Equations
l The substances on the left side of the arrow are called the reactants. They are the starting materials in the reaction.
l The substances on the right side of the arrow are called the products. They are the ending materials in a reaction.
A + B C + D
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Examples of Chemical Equations
2 2 2
2 2 2 2
2 2 3
2 2
3 2
H O H O
H O H O
N H NH
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Signs of a Chemical Change
l Gas production – bubbles, odor, fizz, smoke
l Color change
l Release or absorption of energy – light or temperature change
l Formation of a precipitate – a solid substance that falls out of solution
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Law of Conservation of Matter
l Matter is neither created nor destroyed, it just changes forms.
l Ex.: Where does matter go when you burn a piece of paper?
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Describing Matter
l Volume – The amount of space an object takes up
l Measurement Device: ruler or graduated cylinder
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Describing Matter
l Mass-The amount of matter in an objectl Measurement Device: Balance
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Describing Matter
l Weight – a measure of the gravitational force exerted on an object
l Changes with your location in the universe
l Compare mass and weight of a person on earth and on the moon
Weight vs. Mass Demo
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Types of Measurements
l Qualitative: Describes something using the 5 senses
l Quantitative: Uses numbers in the description
¡ Quantity – something that has magnitude, size, or amount.
¡ Unit – a quantity adopted as a standard of measurement
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International System of Measurements
l Based upon multiples of 10l 7 metric units are base units.
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Origin of the Metric System
l During the18th century scientists measured the distance from the earth’s equator to the North Pole and divided it into ten million parts.
l This number is equal to exactly 1 meter.
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Metric Units
l Mass kilogram kg balance
l Length meter m ruler
l Timesecond s clock
l Temp. Kelvin K thermometer
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The Meter
l The original standard for the meter was kept in a safe in France.
l The meter stick is a replica of that standard.
l A meter is made up of 100 centimeters and 1000 millimeters.
l Lasers are now used to determine the standard for a meter.
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The Gram
l Mass is the amount of matter in an object.
l 1 cm3 of water = 1 gram.
l The standard kilogram is kept under lock and key in Washington, DC and other cities around the world.
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Derived Units: Units that come from other unitsl Area meters squared m2
ruler l x w
l Volume meters cubed m3
ruler or graduated cylinder l x w x h
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The Liter
l The liter is 1000 mLl 10cm x 10cm x 10cml 1 liter = 1000 cm3 = 1 dm3
l 1 milliliter = 1 cm3 = 1 cc = 20 drops
=
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Metric (SI) Prefixesl Mega M 1,000,000l Kilo k 1,000l Hecto h 100l Deka da 10l BASE UNITl Deci d .1l Centi c .01l Milli m .001l Micro µ .000001l Nano n .000000001l Pico p .0000000000001
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Properties of Matter
l Physical = A characteristic of a substance that does not involve a chemical change
l Examples: texture, state of matter, density, hardness, boiling point
l Density = The ratio of the mass of a substance to the volume of the substance.
l D = mass / volume
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Density Column
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Density
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Which is more dense: Diet or Regular Soda?
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Density of an Irregular solid:
1- Find the mass of the object2- Find the volume if the object by water
displacement!
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Properties of Matter
l Chemical = A property of matter that describes a substance’s ability to participate in chemical reactions.
l Examples: reacting with oxygen, light sensitivity
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Classification of Matter
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Classification of Matter
l Pure substances: A sample of matter with a definite composition; means definite chemical and physical properties.
l Includes: Elements and Compounds
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Elements
l Made up of one type of atom.
l An atom is defined as the smallest unit of an element that maintains the properties of that element.
l Cannot be separated into similar substances by chemical means.
l Represented by symbols.
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Elements (cont.)
l Can exist as atoms or molecules. A molecule usually consists of two or more atoms.
l Ex. N2, O2, F2, Cl2, Br2, I2, H2
l Elements that have more than one form are called allotropes.
l Ex. Carbon (graphite and diamond)
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Compounds
l Made up of 2 or more different elements combined in a fixed position.
l Can be separated through chemical means.
l Represented by formulas.
l Electrolysis allows chemists to distinguish between elements in compounds.
l Examples: CO2 and H2O
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Elements Vs. Compounds
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Mixtures: A combination of 2 or more substances that are not chem. combined.
l Heterogeneous Mixture: Composed of dissimilar components; Can see the parts
l Ex. Cookie, salad, asphalt
l Homogenous Mixture: Uniform structure or composition throughout
l Ex. Lemonade, steel, air
l Alloy: A solid homogeneous mixture (14 caret gold, steel, pewter)
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Examples of Alloys
Brass is an alloy of copper and zinc.
Steel is an alloy of carbon and iron.
Bronze is an alloy of copper and tin.
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Microscopic look at mixtures
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Separating Heterogeneous Mixtures
l Filtration: Pour liquid through paper and collect residue (solid)
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Separation of Homogeneous Mixtures
l Distillation: Separation based on a difference in boiling points
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Another Look at Distillation
l Distillation Demol A Closer Look at Distillation
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Separation of Homogeneous Mixtures
l Crystallization: Evaporate liquid and solid will recrystallize
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Separation of Homogeneous Mixtures
l Chromatography: Separation of pigments of dye