Changes in Matter

Introduction to Chemistry

Classifying Matter

Matter: is anything that has mass and volume.

Volume: the amount of spacethat something takes up

Property: a characteristic of a material that can be used in its identification

e.g. colour ,texture, state, density, boiling point, melting point etc.

Examples

Give all properties you can think of for

water

Liquid

Clear

Boils at 100’C

Freezes at 0’C

Density is 1g/ml

All matter is composed

of atoms. Atoms are the

smallest complete

building block of

matter

Atoms are composed of

smaller particles called

protons, neutrons, and

electrons.

Inside the Atom.

Inside the Atom.

positive

negative

neutral

Pure Substances

A pure substance is something which is composed of only one type of particle

Particle: an atom or molecule

eg. copper wire,

plastic

Elements:

– A pure substance that cannot be changed

into anything simpler

– eg. gold, silver, oxygen

The Classification of Matter

Elements When atoms of only one kind are grouped together

you have an element. Elements are listed on the periodic table. There are just over 100 different elements in the universe.

Compounds

– . A pure substance that consists of two or

more different types of atoms chemically bonded

together to make one type of molecule

– The elements are in definite proportions

and cannot be separated by physical

means

– eg. Pure water or H2O

– Made of 2 hydrogen atoms and 1 oxygen atoms

but the only molecule is H2O

Hydrogen

oxygen

Matter

Pure SubstanceMixture

Element Compound

•two or more types of

atoms but only one type

of molecule

e.g. H2O

•Only one type of

atom

e.g. Mg

Mixtures vs. Pure Substances Water is a compound and a pure substance. Kool

Aid is a solution and a mixture.

You can’t change the properties of water like its taste or colour because it’s only made up of one type of substance (H2O molecules).

You can change the properties of Kool Aid. You can make it sweeter or lighter in colour because you can alter the amounts of each different type substance in it. E.g. more sugar, or more water etc.

Not on your notes

Mixtures:– Contain two or more pure substances

– Eg. salt dissolved in water

Kool Aid is a mixture because it’s made

up of water molecules, sugar molecules,

and food colouring molecules

Mixtures

Variable combination of two or more

pure substances.

Heterogeneous Homogeneous

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Homogenous mixtures:

– Made up of substances that are evenly and

microscopically mixed together

These are called solutions (look like one thing).

eg. Pop, chocolate milk

Mixtures

Solution

– homogeneous

– very small particles

– no Tyndall effect Tyndall Effect

– particles don’t settle

– EX: rubbing alcohol

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Mixtures - Solutions Solutions look like they’re only made of one thing

but…

Salt water (liquid Solution)

made of salt molecules and

water molecules

Steel (Solid Solution)

Made of iron atoms, nickel atoms,

chromium atoms, carbon atoms

Air (gas solution) made up of many different types of atoms and molecules such Oxygen, Carbon Dioxide and Nitrogen.

Component Symbol Volume

Nitrogen N2 78.0%

99.9%

Oxygen O2 20.9%

Argon Ar 0.9%

Carbon Dioxide

CO2 0.03%

Composition

of Air

Component Symbol Volume

Nitrogen N2 78.084%

99.998%

Oxygen O2 20.947%

Argon Ar 0.934%

Carbon Dioxide CO2 0.033%

Neon Ne 18.2 parts per million

Helium He 5.2 parts per million

Krypton Kr 1.1 parts per million

Sulfur dioxide SO2 1.0 parts per million

Methane CH4 2.0 parts per million

Hydrogen H2 0.5 parts per million

Nitrous Oxide N2O 0.5 parts per million

Xenon Xe 0.09 parts per million

Ozone O3 0.07 parts per million

Nitrogen dioxide NO2 0.02 parts per million

Iodine I2 0.01 parts per million

Carbon monoxide CO trace

Ammonia NH3 trace

Composition

of Air

The Classification of Matter

Heterogeneous Mixtures:

– A mixture that is not uniform in its composition

– A suspension is a liquid and solid that doesn’t mix like flour and water

– A colloid are medium sized particles that don’t settle like fog or milk.

– A mechanical mixture is a mixture of solids that can be seen.

– eg.salad

Mixtures

Suspension

– heterogeneous

– large particles

– Tyndall effect

– particles settle

– EX: fresh-squeezed

lemonade

Mixtures

Colloid

– heterogeneous

– medium-sized particles

– Tyndall effect

– particles don’t settle

– EX: milk

Matter

Pure SubstanceMixture

Element Compound

Mechanical Suspensions Solutions

nuts n’ bolts

saladflour and water

Large particles

air

salt water

1 kind of atomAtom A Atom B

ColloidsMedium size

particles

Physical and Chemical Changes

In a physical change no new substances are

formed

Physical changes include changes of state.

liquid to solid: Solidifying or Freezing

solid to liquid: Melting

liquid to gas: Evaporation or Boiling

gas to liquid: Condensation

gas to solid : deposition

or solid to gas: Sublimation

Changes of State

gas

liquid

solid

sublimation deposition

condensing evaporating

Changes of State

gas

liquid

solid

sublimation deposition

condensing evaporating

solidifying / freezing

melting

When a change of state occurs,

molecules or atoms may move faster or

slower, may spread out or clump

together, but they do not change.

i.e. An H2O molecule is still an H2O

molecule!

Physical Change

Kinetic Molecular Theory

1) All matter is made up of tiny particles

2) Different substances have different particles

3) The particles are in constant motion

4) The more energy the particles have, the faster they move

5) The attraction between particles decreases with distance

Solids– Particles are very close

– Particles are constantly vibrating in place

– Attraction between particles is high but decreases

as vibration increases

Liquids– Increase in energy from solids, increased amount

of vibration

– Particles are still close together

– Particles can move freely within the container

– Attraction still quite high, but less than solids and

decreasing with distance apart

Gases

– Increase in energy from liquids,

increase in vibration & movement

of particles

– Particle are very far apart

– Particles vibrate, rotate, bump

into each other in a very rapid

straight line motion

– Increase in energy causes an increase in

pressure

• Increase in speed and number of particles

hitting the sides of containers

– No attractive force between the particles,

they are too far apart and moving too

fast

Chemical change results in a new

substance being produced with different

chemical and physical properties.

In short, a chemical reaction takes place

e.g. frying an egg

Chemical Change

Physical changes can usually be

reversed, whereas chemical changes

cannot

Chemical Change

Clues that a Chemical Reaction

Might Have Occurred:

Colour change

Heat or light given off

Odour given off

Gas released

Solid forming in a liquid

Difficult to reverse

Identifying Chemical and

Physical Change

Physical Chemical

Reversible Often Not usually

New substance No Yes

Properties Stay the same New

Energy change May occur, but

not noticeable

May occur, often

noticeable

Chemical vs Physical Properties

Physical Properties describe a substances

physical state - solid, liquid or gas

appearance – colour, texture, smell

density, melting and boiling points

Chemical Properties describe a substances’ behavior

in a reaction.

Example = flammable, poisonous, highly reactive

corrosive,

Observations of matter

Qualitative vs Quantitative

Colour

Smell

Shape

Texture

Mass

volume

Chemical Reactions

A chemical change means that a chemical reaction has occurred.

In a chemical reaction one or more substances (reactants) change to one or more new substances (products)

Energy is either released OR absorbed in every chemical reaction

In a word equation, reactants are listed on the leftand products on the right. They are separated by an arrow pointing to the right.

H2 + O2 H2O

reactants products

The means reacts to form

The + means and

Practice – write the word equation

Aluminum reacts with oxygen to form

aluminum oxide.

aluminum + oxygen aluminum oxide

Practice – write the word equation

In our bodies we use glucose and oxygen to produce

carbon dioxide, water and ATP.

glucose + oxygen carbon dioxide + water + ATP

Two Types of Chemical Reactions

You Know About

Corrosion: metal reacting with oxygen

and water to form rust

Combustion: is the burning of a

substance (fuel) in the presence of

oxygen. Products are carbon dioxide

and water

In a chemical reaction atoms rearrange to

form new substances.

HCl + NaHCO3 → H2O + CO2 + NaCl

the total mass of the reactants is equal to the

total mass of the products because no atoms

are created or destroyed…only rearranged!

This is the Law of Conservation of Mass.

When the reaction involves gases it is difficult to prove that mass is conserved if you are using an open system because the gas can escape!

A closed system (a sealed container) is needed to prove the Law of Conservation of Mass!

Endothermic vs Exothermic Reactions

All reactions either give off energy or absorb

energy.

Endothermic reactions absorb energy and the

surroundings can get cooler.

Exothermic reactions release energy the

surroundings get warmer like in combustion and

burning.