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.