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Chapter 1
Chemistry: The Study of Matter
What is Chemistry?
The study of matter, its composition, properties, and the changes it undergoes
Applied Chemistry is the using of chemistry to attain certain goals, in fields like medicine, agriculture, and manufacturing
Pure Chemistry gathers knowledge for knowledge sake
Branches of ChemistryAnalytical Chemistry -studies composition of substances.Organic Chemistry -compounds containing carbonInorganic Chemistry -substances without carbonBiochemistry- Chemistry of living thingsPhysical Chemistry studies behavior of substances rates and mechanisms of reactions energy transfers
Chemistry is
A natural science
A language with its own vocabulary
A way of thinking
Scientific Method
A way of solving problems or answering questions
Starts with observation- noting and recording facts
Hypothesis- an educated guess as to the cause of the problem or answer to the question
Scientific Method
Experiment- designed to test the hypothesisOnly two possible answers 1) hypothesis is right2) hypothesis is wrongGenerates data observations from experimentsModify hypothesis- repeat the cycle
Variables
Controlled experiment- Only want one thing to change at a time in a laboratory.
Manipulated variable- What you change or control directly
Also called independent variable
Responding variable – What changes as a result. No direct control
Also called dependent variable
Prediction
Experiment
Modify
Observations
Hypothesis
Experiment
Law
Theory(Model)
Observations
Hypothesis
Experiment
Cycle repeats many times.
The hypothesis gets more and more certain.
Becomes a theory
A thoroughly tested model that explains why things behave a certain way.
Theory can never be proven.
Useful because they predict behavior
Help us form mental pictures of processes (models)
Observations
Hypothesis
Experiment
Another outcome is that certain behavior is repeated many times
Scientific Law is developed
Description of how things behave
Law - how
Theory- why
Observations
Hypothesis
Experiment
Law
Theory(Model)
Prediction
Experiment
Modify
Observations
Hypothesis
Experiment
Law vs. Theory
Theory can’t be proved; always the possibility that a new experiment will disprove a theory
Law described a natural phenomenon, but does not attempt to explain it
Frame of Reference
What is it?
Physics Definition- system of objects that are not moving with respect to one another
Dictionary Definition- set of ideas, facts, or circumstances within which something exists.
What does Frame of Reference mean to the world of Chemistry?
What is Matter?
Matter is anything that takes up space and has mass
Mass is the amount of matter in an object
Mass is resistance to change in motion along a smooth and level surface
Types of Matter
Substance- a particular kind of matter – pure
Mixture- more than one kind of matter
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MatterWe define matter as anything that has mass and takes up space.
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Matter
Atoms are the building blocks of matter.
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Matter
Atoms are the building blocks of matter. Each element is made of the same kind of atom.
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Matter
Atoms are the building blocks of matter. Each element is made of the same kind of atom. A compound is made of two or more different kinds of elements.
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Classification of Matter
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Properties and Changes of Matter
Properties
Words that describe matter (adjectives)Physical Properties- a quality or condition of a substance that can be observed or measured without changing the substance’s compositionChemical Properties- a property that can be observed by changing the type of substance
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Types of PropertiesIntensive Properties…Are independent of the amount of the
substance that is present.Density, boiling point, color, etc.
Extensive Properties…Depend upon the amount of the substance
present.Mass, volume, energy, etc.
Examples of Physical Properties
1) Color2) Solubility3) Odor4) Hardness5) Density6) Melting Point7) Boiling Point8) Size9) Shape
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Types of ChangesPhysical ChangesThese are changes in matter that do not
change the composition of a substance.Changes of state, temperature, volume, etc.
Chemical ChangesChemical changes result in new substances.
Combustion, oxidation, decomposition, etc.
Physical Changes
Physical Change- alters a substance without changing its composition
Key Terms:1. Boil2. Freeze3. Dissolve4. Melt5. Condense6. Break7. Split8. Crack9. Crush10. Cutting
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Chemical Reactions
In the course of a chemical reaction, the reacting substances are converted to new substances.
Chemical Reactions
One or more substances changing into a new substance
Starting Substance- Reactant
New Substance- Product
Iron + Sulfur Iron Sulfide
How do you know?
6 Ways to TellI. Color ChangeII. Energy absorbed or released (temp
change)III. Gas or Solid ProducedIV. OdorV. Precipitate (ppt)- solid that separates from
solutionVI. Not easily reversed
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States of Matter
States of Matter
Solid- matter that has a definite shape and volumeLiquid- matter that flows and has a fixed volumeGas- matter that takes up both the shape and volume of a containerVapor- a substance that is currently a gas but normally is a liquid or solid at room temperature.Plasma- matter consisting of a gaseous mixture of electrons and positive ions. Not found on Earth
States of MatterStates of Matter
Solid
Liquid
Gas
Definite Volume?
YES
YES
NO
Definite Shape?
YES
NO
NO
Temp. increase
Small Expans.
Small Expans.
Large Expans.
Com-pressible?
NO
NO
YES
Matter Chart
Properties: Solid Liquid Gas or Vapor
Mass Definite Definite Definite
Shape Rigid Indefinite Indefinite
Volume Definite Definite Indefinite
Temp. Increase
Small Expansion
Moderate Expansion
Large Expansion
Com-
Pressible?
No No Yes
Solid Liquid Gas
Melt Evaporate
CondenseFreeze
Mixtures
Mixture- Physical blend of two or more substancesMixture has variable compositionTwo Types of Mixtures
Heterogeneous- not uniform in composition
Homogeneous- completely uniform in compostion
Example
Heterogeneous
I. Blood
II. Chocolate Chip Cookie
III. Soil
IV. Blood
V. Mixed Salad
Homogeneous
I. Air
II. Brass
III. Black Coffee
IV. Motor Oil
V. Water
Solutions
Homogeneous Mixture
Mixed molecule by molecule
Example: Sugar in Water (same composition as any other portion)
Can occur between any state of matter
Common Solutions
Gas in Gas- O2 in N (air)
Liquid in Gas- Water Vapor Gas in Liquid- CO2 in Water (soda water)
Liquid in Liquid- Acetic Acid in Water (vinegar)
Solid in Liquid- Kool Aid Solid in Solid- Copper in Silver (sterling
silver)
Solutions
Like all mixtures, they keep the properties of the components
Can by separated by physical means
Not easily separated- can be separated
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Separation of Mixtures
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Distillation
Distillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components.
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Filtration
In filtration solid substances are separated from liquids and solutions.
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Chromatography
This technique separates substances on the basis of differences in solubility in a solvent.
Separating mixturesOnly a physical change- no new matterFiltration- separate solids from liquids with a barrierDistillation- separate because of different boiling pointsHeat mixtureCatch vapor in cooled area
Chromatography- different substances are attracted to paper or gel, so move at different speeds
The Metric System
Measuring
The numbers are only half of a measurement.
It is 10 long.
10 what?
Numbers without units are meaningless.
How many feet in a yard?
A mile?
A rod?
The Metric System
Easier to use because it is a decimal system.
Every conversion is by some power of 10.
A metric unit has two parts.
A prefix and a base unit.
prefix tells you how many times to divide or multiply by 10.
Base Units
Length - meter - more than a yard - m
Mass - grams - about a raisin - g
Time - second - s
Temperature - Kelvin or ºCelsius K or ºC
Energy - Joules- J
Volume - Liter - half of a two liter bottle- L
Amount of substance - mole - mol
Prefixesgiga- G 1,000,000,000 109
mega - M 1,000,000 106
kilo - k 1,000 103
deci-d 0.1 10-1
centi- c 0.01 10-2
milli- m 0.001 10-3
micro- 0.000001 10-6
nano- n 0.000000001 10-9
Volume
calculated by multiplying L x W x H Liter the volume of a cube 1 dm (10 cm) on a side1L = 1 dm3
so 1 L = 10 cm x 10 cm x 10 cm
1 L = 1000 cm3
1/1000 L = 1 cm3
1 mL = 1 cm3
Conservation of Mass
Law of Conservation of Mass- in a physical or chemical reaction, mass is neither created nor destroyed; it is conserved.
All mass can be accounted for.
Mass of the Reactants = Mass of Products
Mass and Weight
Mass is measure of resistance to change in motion
Weight is force of gravity.
Sometimes used interchangeably
Mass can’t change, weight can
Mass
Weight is a force. Mass is the amount of matter.
1 gram is defined as the mass of 1 cm3 of water at 4 ºC.
1000 g = 1000 cm3 of water
1 kg = 1 L of water
1 kg = 2.5 lbs
Converting
k h D d c mhow far you have to move on this chart, tells you how far, and which direction to move the decimal place.
The box is the base unit, meters, Liters, grams, etc.
Conversions
convert 25 mg to grams
convert 0.45 km to mm
convert 35 mL to liters
It works because the math works, we are dividing or multiplying by 10 the correct number of times.
k h D d c m
UncertaintyBasis for significant figures
All measurements are uncertain to some degree
Precision- how repeatable
Accuracy- how correct - closeness to true value.
Random error - equal chance of being high or low- addressed by averaging measurements - expected
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Accuracy versus Precision
Accuracy refers to the proximity of a measurement to the true value of a quantity.
Precision refers to the proximity of several measurements to each other.
UncertaintySystematic error- same direction each timeWant to avoid thisBad equipment or bad technique.Better precision implies better accuracyYou can have precision without accuracyYou can’t have accuracy without precision (unless you’re really lucky).
Dimensional Analysis
Using the units to solve problems
Dimensional AnalysisUse conversion factors to change the units
Conversion factors = 1
1 foot = 12 inches (equivalence statement)
12 in = 1 = 1 ft.
1 ft. 12 in
2 conversion factors
multiply by the one that will give you the correct units in your answer.
Examples11 yards = 2 rod
40 rods = 1 furlong
8 furlongs = 1 mile
The Kentucky Derby race is 1.25 miles. How long is the race in rods, furlongs, meters, and kilometers?
A marathon race is 26 miles, 385 yards. What is this distance in rods and kilometers?
Because you never learned dimensional analysis, you have been working at a fast food restaurant for the past 35 years wrapping hamburgers. Each hour you wrap 184 hamburgers. You work 8 hours per day. You work 5 days a week. you get paid every 2 weeks with a salary of $840.34. How many hamburgers will you have to wrap to make your first one million dollars?
Examples
A senior was applying to college and wondered how many applications she needed to send. Her counselor explained that with the excellent grade she received in chemistry she would probably be accepted to one school out of every three to which she applied. She immediately realized that for each application she would have to write 3 essays, and each essay would require 2 hours work. Of course writing essays is no simple matter. For each hour of serious essay writing, she would need to expend 500 calories which she could derive from her mother's apple pies. Every three times she cleaned her bedroom, her mother would made her an apple pie. How many times would she have to clean her room in order to gain acceptance to 10 colleges?
Units to a Power
How many m3 is 1500 cm3?
1500 cm33 1 m100 cm
1 m100 cm
1 m100 cm
1500 cm33 1 m
100 cm
33
Units to a Power
How many cm2 is 15 m2?
36 cm3 is how many mm3?
Multiple unitsThe speed limit is 65 mi/hr. What is this in m/s?1 mile = 1760 yds 1 meter = 1.094 yds
65 mihr
1760 yd1 mi 1.094 yd
1 m 1 hr60 min
1 min60 s
Multiple units
Lead has a density of 11.4 g/cm3. What is this in pounds per quart?454 g = 1 lb1 L = 1.094 qt
Temperature and Density
Density
How heavy something is for its size.
The ratio of mass to volume for a substance.
D = M / V
Independent of how much of it you have
gold - high density
air low density.
Density
Ratio of mass to volume
D = m/V
Useful for identifying a compound
Useful for predicting weight
An intrinsic property- does depend on what the material is
Calculating
The formula tells you how.
Units will be g/mL or g/cm3
A piece of wood has a mass of 11.2 g and a volume of 23 mL what is the density?
A piece of wood has a density of 0.93 g/mL and a volume of 23 mL what is the mass?
Density Problem
An empty container weighs 121.3 g. Filled with carbon tetrachloride (density 1.53
g/cm3 ) the container weighs 283.2 g. What is the volume of the container?
Density Problem
A 55.0 gal drum weighs 75.0 lbs. when empty. What will the total mass be when filled with ethanol?
density 0.789 g/cm3 1 gal = 3.78 L 1 lb = 454 g
Floating
Lower density floats on higher density.
Ice is less dense than water.
Most wood is less dense than water.
Helium is less dense than air.
A ship is less dense than water.
Density of water
1 g of water is 1 mL of water.
density of water is 1 g/mL
at 4ºC
otherwise it is less
Temperature
A measure of the average kinetic energy
Different temperature scales, all are talking about the same height of mercury.
Derive a equation for converting ºF toºC
Measuring Temperature
Celsius scale.
water freezes at 0ºC
water boils at 100ºC
body temperature 37ºC
room temperature 20 - 25ºC
0ºC
0ºC 32ºF
0ºC = 32ºF
100ºC 212ºF
100ºC = 212ºF
0ºC = 32ºF
0ºC 32ºF
100ºC 212ºF0ºC 32ºF
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF
How much it changes
100ºC 212ºF0ºC 32ºF
100ºC = 212ºF
0ºC = 32ºF
100ºC = 180ºF1ºC = (180/100)ºF
1ºC = 9/5ºF
How much it changes
ºC
ºF 9
5
0ºC is not 0ºF
ºC
ºF
(0,32)= (C1,F1)
ºC
ºF
(0,32) = (C1,F1)
(100,212) = (C2,F2)
Measuring Temperature
Kelvin starts at absolute zero (-273 º C)
degrees are the same size
C = K -273
K = C + 273
Kelvin is always bigger.
Kelvin can never be negative.
273 K
Temperature is different
from heat.
Temperature is which way heat will flow. (from hot to cold)
Heat is energy, ability to do work.
A drop of boiling water hurts,
kilogram of boiling water kills.
Units of heat are
calories or Joules
1 calorie is the amount of heat needed to raise the temperature of 1 gram of water by 1ºC.
A food Calorie is really a kilocalorie.
How much energy is absorbed to heat 15 grams of water by 25ºC.
1 calorie = 4.18 J
Elements & Compounds
Element- simplest form of matter
I. Elements can’t be separated
II. Elements are the building block
III. Smallest part is an atom
Compounds
Compound- formed by 2 or more elementsI. Substances that can be separated into
simpler substances only by chemical reactions
II. When broken down, the pieces have completely different properties than the compound
III. Pure substancesIV. Represented by a formulaV. Smallest part is a molecule
Compound or MixtureCompound Mixture
One kind of piece-Molecules
More than one kind - Molecule or atoms
Making is a chemical change
Making is a physical change
Only one kind Variable composition
What is it?
Element, Compound or Mixture
1. Silver
2. Orange Juice
3. Ice Tea
4. Potassium Chloride
5. Oxygen
6. Air
7. Pine Tree
Which is it?
ElementCompoundMixture