chapter 1 chemistry: the study of matter. what is chemistry? the study of matter, its composition,...

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