tro3 lecture 03[1]

Tro's "Introductory Chemistry", Chapter 3

1

What Is Matter?• Matter is defined as

anything that occupies space and has mass.

• Even though it appears to be smooth and continuous, matter is actually composed of a lot of tiny little pieces we call atoms and molecules.


2

Atoms and Molecules

• Atoms are the tiny particles that make up all matter.

• In most substances, the atoms are joined together in units called molecules.The atoms are joined in

specific geometric arrangements.


3

Classifying Matterby Physical State

• Matter can be classified as solid, liquid, or gas based on what properties it exhibits.

State Shape Volume Compress Flow

Solid Fixed Fixed No No

Liquid Indefinite Fixed No Yes

Gas Indefinite Indefinite Yes Yes

• Fixed = Property doesn’t change when placed in a container. • Indefinite = Takes the property of the container.


4

Solids• The particles in a solid are packed

close together and are fixed in position.Although they may vibrate.

• The close packing of the particles results in solids being incompressible.

• The inability of the particles to move around results in solids retaining their shape and volume when placed in a new container and prevents the particles from flowing.


5

Liquids• The particles in a liquid are closely packed,

but they have some ability to move around. • The close packing results in liquids being

incompressible.• The ability of the particles to move allows

liquids to take the shape of their container and to flow. However, they don’t have enough freedom to escape and expand to fill the container.


6

Gases

• In the gas state, the particles have complete freedom from each other.

• The particles are constantly flying around, bumping into each other and the container.

• In the gas state, there is a lot of empty space between the particles.On average.


7

Classification of Matter by Appearance

• Homogeneous = Matter that is uniform throughout. Appears to be one thing. Every piece of a sample has identical properties, though another sample

with the same components may have different properties. Solutions (homogeneous mixtures) and pure substances.

• Heterogeneous = Matter that is non-uniform throughout . Contains regions with different properties than other regions.


8

Practice—Classify the Following as Homogeneous or Heterogeneous

• Table sugar.

• A mixture of table sugar and black pepper.

• A mixture of sugar dissolved in water.

• Oil and vinegar salad dressing.


9

Practice—Classify the Following as Homogeneous or Heterogeneous,

Continued• Table sugar = homogeneous

• A mixture of table sugar and black pepper = heterogeneous

• A mixture of sugar dissolved in water = homogeneous

• Oil and vinegar salad dressing = heterogeneous


10

Classifying Matterby Composition

• Matter that is composed of only one kind of atom or molecule is called a pure substance.

• Matter that is composed of different kinds of atoms or molecules is called a mixture.

• Because pure substances always have only one kind of piece, all samples show the same properties.

• However, because mixtures have variable composition, different samples will show different properties.


11

Classification of Matter

• Pure Substance = All samples are made of the same pieces in the same percentages. Salt

• Mixtures = Different samples may have the same pieces in different percentages. Salt water

Pure SubstanceConstant Composition

Homogeneous

MixtureVariable Composition

Matter


12

Pure Substances vs. MixturesPure Substances

1. All samples have the same physical and chemical properties.

2. Constant composition = All samples have the same pieces in the same percentages.

3. Homogeneous.4. Separate into components

based on chemical properties.

5. Temperature stays constant while melting or boiling.

Mixtures1. Different samples may show

different properties.2. Variable composition =

Samples made with the same pure substances may have different percentages.

3. Homogeneous or heterogeneous.

4. Separate into components based on physical properties.

5. Temperature usually changes while melting or boiling because composition changes.


13

Classification of Pure Substances• Substances that cannot be broken down into simpler

substances by chemical reactions are called elements.Basic building blocks of matter.Composed of single type of atom.

Although those atoms may or may not be combined into molecules.

• Substances that can be decomposed are called compounds.Chemical combinations of elements.

Although properties of the compound are unrelated to the properties of the elements in it!

Composed of molecules that contain two or more different kinds of atoms.

All molecules of a compound are identical, so all samples of a compound behave the same way.

• Most natural pure substances are compounds.


14

Atoms and Molecules• Atoms

Are submicroscopic particles that are the unit pieces of elements.

Are the fundamental building blocks of all matter.

• MoleculesAre submicroscopic particles that are the

unit pieces of compounds. Two or more atoms attached together.

Attachments are called bonds.Attachments come in different strengths.

Molecules come in different shapes and patterns.


15

Classification of Pure Substances

1. Made of one type of atom. (Some elements are found as multi-atom molecules in nature.)

2. Combine together to make compounds.

1. Made of one type of molecule, or array of ions.

2. Molecules contain 2 or more different kinds of atoms.

Elements Compounds


16

Practice—Classify the Following as Elements or Compounds

• Chlorine, Cl2

• Table sugar, C12H22O11

• A red solid that turns blue when heated and releases water that is always 30% of the solid’s mass.

• A brown-red liquid that, when energy is applied to it in any form, causes only physical changes in the material, not chemical.


17

Practice—Classify the Following as Elements or Compounds, Continued

• Chlorine, Cl2 = element.

• Table sugar, C12H22O11 = compound.

• A red solid that turns blue when heated and releases water that is always 30% of the solid’s mass = compound.

• A brown-red liquid that, when energy is applied to it in any form, causes only physical changes in the material, not chemical = element.


18

Classification of Mixtures

• Mixtures are generally classified based on their uniformity.

• Mixtures that are uniform throughout are called homogeneous.Also known as solutions.Mixing is on the molecular level.

• Mixtures that have regions with different characteristics are called heterogeneous.


19

Classification of Mixtures, Continued

1. Made of multiple substances, but appears to be one substance.

2. All portions of a sample have the same composition and properties.

1. Made of multiple substances, whose presence can be seen.

2. Portions of a sample have different composition and properties.

Heterogeneous Homogeneous

20

Classifying Matter


21

Properties Distinguish Matter

• Each sample of matter is distinguished by its characteristics.

• The characteristics of a substance are called its properties.

• Some properties of matter can be observed directly.

• Other properties of matter are observed when it changes its composition.


22

Properties of Matter• Physical Properties are the characteristics of matter

that can be changed without changing its composition.Characteristics that are directly observable.

• Chemical Properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy. Characteristics that describe the behavior of matter.


23

Changes in Matter• Changes that alter the state or appearance of the

matter without altering the composition are called physical changes.

• Changes that alter the composition of the matter are called chemical changes.

During the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present.


24

Changes in Matter, Continued• Physical Changes—Changes in

the properties of matter that do not effect its composition.Heating water.

Raises its temperature, but it is still water.

Evaporating butane from a lighter.Dissolving sugar in water.

Even though the sugar seems to disappear, it can easily be separated back into sugar and water by evaporation.


25

Changes in Matter, Continued• Chemical Changes involve a change

in the properties of matter that change its composition.A chemical reaction.Rusting is iron combining with oxygen to

make iron(III) oxide.Burning results in butane from a lighter to

be changed into carbon dioxide and water.Silver combines with sulfur in the air to

make tarnish.


26

Is it a Physical or Chemical Change?• A physical change results in a different form of the

same substance.The kinds of molecules don’t change.

• A chemical change results in one or more completely new substances.Also called chemical reactions.

The new substances have different molecules than the original substances.

You will observe different physical properties because the new substances have their own physical properties.


27

Phase Changes ArePhysical Changes

• Boiling = liquid to gas.• Melting = solid to liquid.• Subliming = solid to gas.• Freezing = liquid to solid.• Condensing = gas to liquid.• Deposition = gas to solid.• State changes require heating or cooling the substance.

Evaporation is not a simple phase change, it is a solution process.


28

Practice—Classify Each Change as Physical or Chemical

• Evaporation of rubbing alcohol.• Sugar turning black when heated.• An egg splitting open and spilling out.• Sugar fermenting.• Bubbles escaping from soda.• Bubbles that form when hydrogen peroxide is

mixed with blood.


29

Practice—Classify Each Change as Physical or Chemical, Continued

• Evaporation of rubbing alcohol = physical.• Sugar turning black when heated = chemical.• An egg splitting open and spilling out =

physical.• Sugar fermenting = chemical.• Bubbles escaping from soda = physical. • Bubbles that form when hydrogen peroxide is

mixed with blood = chemical.


30

Separation of Mixtures• Separate mixtures based on different

physical properties of the components.Physical change.

Centrifugation and

decanting

Density

EvaporationVolatility

ChromatographyAdherence to a surface

FiltrationState of matter (solid/liquid/gas)

DistillationBoiling point

TechniqueDifferent Physical Property


31

Distillation


32

Filtration


33

Law of Conservation of Mass• Antoine Lavoisier• “Matter is neither created nor destroyed in a

chemical reaction.”• The total amount of matter present before a

chemical reaction is always the same as the total amount after.

• The total mass of all the reactants is equal to the total mass of all the products.


34

Conservation of Mass• Total amount of matter remains constant in a

chemical reaction.• 58 grams of butane burns in 208 grams of oxygen to

form 176 grams of carbon dioxide and 90 grams of water.

butane + oxygen carbon dioxide + water 58 grams + 208 grams 176 grams + 90 grams

266 grams = 266 grams


35

Energy• There are things that do not have mass and

volume.• These things fall into a category we call energy.• Energy is anything that has the capacity to do

work.• Although chemistry is the study of matter, matter

is effected by energy.It can cause physical and/or chemical changes in

matter.


36

Law of Conservation of Energy

• “Energy can neither be created nor destroyed.” • The total amount of energy in the universe is

constant. There is no process that can increase or decrease that amount.

• However, we can transfer energy from one place in the universe to another, and we can change its form.


37

Matter Possesses Energy• When a piece of matter

possesses energy, it can give some or all of it to another object.It can do work on the other

object.

• All chemical and physical changes result in the matter changing energy.


38

Kinds of EnergyKinetic and Potential

• Potential energy is energy that is stored. Water flows because gravity pulls it

downstream. However, the dam won’t allow it to

move, so it has to store that energy.• Kinetic energy is energy of motion,

or energy that is being transferred from one object to another. When the water flows over the dam,

some of its potential energy is converted to kinetic energy of motion.


39

Some Forms of Energy• Electrical

Kinetic energy associated with the flow of electrical charge.

• Heat or Thermal EnergyKinetic energy associated with molecular motion.

• Light or Radiant EnergyKinetic energy associated with energy transitions in an

atom.• Nuclear

Potential energy in the nucleus of atoms. • Chemical

Potential energy in the attachment of atoms or because of their position.


40

Converting Forms of Energy• When water flows over the dam, some of its

potential energy is converted to kinetic energy.Some of the energy is stored in the water because it is

at a higher elevation than the surroundings. • The movement of the water is kinetic energy.• Along the way, some of that energy can be used to

push a turbine to generate electricity.Electricity is one form of kinetic energy.

• The electricity can then be used in your home. For example, you can use it to heat cake batter you mixed, causing it to change chemically and storing some of the energy in the new molecules that are made.


41

Units of Energy• Calorie (cal) is the amount of energy needed to

raise one gram of water by 1 °C.kcal = energy needed to raise 1000 g of water 1 °C.food calories = kcals.

Energy Conversion Factors

1 calorie (cal) = 4.184 joules (J)

1 Calorie (Cal) = 1000 calories (cal)

1 kilowatt-hour (kWh) = 3.60 x 106 joules (J)


44

Exothermic Processes

• When a change results in the release of energy it is called an exothermic process.

• An exothermic chemical reaction occurs when the reactants have more chemical potential energy than the products.

• The excess energy is released into the surrounding materials, adding energy to them.Often the surrounding materials get hotter from the

energy released by the reaction.


45

Endothermic Processes

• When a change requires the absorption of energy it is called an endothermic process.

• An endothermic chemical reaction occurs when the products have more chemical potential energy than the reactants.

• The required energy is absorbed from the surrounding materials, taking energy from them.Often the surrounding materials get colder due to the

energy being removed by the reaction.


46

Temperature Scales• Fahrenheit scale, °F.

Used in the U.S.

• Celsius scale, °C.Used in all other countries.A Celsius degree is 1.8

times larger than a Fahrenheit degree.

• Kelvin scale, K.Absolute scale.


47

Fahrenheit vs. Celsius• A Celsius degree is 1.8 times larger than a

Fahrenheit degree.• The standard used for 0° on the Fahrenheit

scale is a lower temperature than the standard used for 0° on the Celsius scale.

1.8

32-F C


48

The Kelvin Temperature Scale• Both the Celsius and Fahrenheit scales have

negative numbers.Yet, real physical things are always positive amounts!

• The Kelvin scale is an absolute scale, meaning it measures the actual temperature of an object.

• 0 K is called absolute zero. It is too cold for matter to exist because all molecular motion would stop.0 K = -273 °C = -459 °F.Absolute zero is a theoretical value obtained by

following patterns mathematically.


49

Kelvin vs. Celsius• The size of a “degree” on the Kelvin scale is the

same as on the Celsius scale.Although technically, we don’t call the divisions on the

Kelvin scale degrees; we call them kelvins!That makes 1 K 1.8 times larger than 1 °F.

• The 0 standard on the Kelvin scale is a much lower temperature than on the Celsius scale.

• When converting between kelvins and °C, remember that the kelvin temperature is always the larger number and always positive!

273C K


52

Specific Heat Capacity• Specific heat is the amount of energy required to raise

the temperature of one gram of a substance by 1 °C. • The larger a material’s specific heat is, the more

energy it takes to raise its temperature a given amount.• Like density, specific heat is a property of the type of

matter. It doesn’t matter how much material you have. It can be used to identify the type of matter.

• Water’s high specific heat is the reason it is such a good cooling agent. It absorbs a lot of heat for a relatively small mass.


53

Heat Gain or Loss by an Object

• The amount of heat energy gained or lost by an object depends on 3 factors: how much material there is, what the material is, and how much the temperature changed.

Amount of Heat = Mass x Heat Capacity x Temperature Change

q = m x C x DT


56

Practice—Calculate the Amount of Heat Released When 7.40 g of Water Cools from 49° to 29 °C

Practice—Calculate the Amount of Heat Released When 7.40 g of Water Cools from 49° to 29 °C,

Continued

q = m ∙ Cs ∙ DT

Cs = 4.18 J/gC (Table 3.4)

The unit and sign are correct.

T1 = 49 °C, T2 = 29 °C, m = 7.40 g

q, J

Check:• Check.

Solution:• Follow the concept plan to solve the problem.

Solution Map:

Relationships:

• Strategize

Given:

Find:

• Sort Information

TC mq s Δ

J 106.2J 64.816

C 02- 4.18g 7.40

Δ

2

CgJ

TCmq s

C 02-

C94 - C 29

12

T

TTT

Cs m, DT q