St. Patrick Fine Arts Elementary
SCIENCE 5
Classroom Chemistry
Name: ____________________________
STUDY NOTES
CHEMISTRY - the study of matter - its properties (what it's like),
its composition (what it's made of),
how it changes
how it interacts.
Matter is anything that takes up space and has mass.
3 main states of matter
SOLID – a state of matter that has a set shape and volume. It doesn’t change if it is
left alone and the temperature doesn’t change.
Examples: wood, solid plastic, solid steel, ice...
LIQUID - a state of matter that has set volume (takes up same space) but no set
shape - it takes the shape of whatever container it is in.
Examples: liquid water, paint, oil, milk...
GAS - (not gasoline) a state of matter that has no set shape - it takes the shape of
whatever container it is in, and no set volume - it can expand or compress
to fill a space.
Examples: water vapour, oxygen, carbon dioxide, helium,...)
The little particles that make up matter in different states
Solid
Liquid
Gas
Shape
Volume
No shape
Volume
No shape
No volume
Very close in structure.
They move very little.
Some matter can change
state depending on the
temperature.
Further apart. They slip and
slide past each other.
Far apart. Free to move.
ATOM - the smallest possible particle of complete matter.
ELEMENT – Matter where all the atoms
inside it are the same.
The Periodic table of Elements
lists the ones we know of.
Examples: gold, silver, oxygen, helium,…
MOLECULE - two or more different atoms connect they form a MOLECULE. Example:
water is made of molecules.
H2O is two hydrogen atoms and
one oxygen atom bound together.
Carbon Dioxide is made of molecules.
CO2 is one carbon atom and two oxygen
atoms bound together.
COMPOUND - matter made of all the same molecules.
Examples of compounds: a glass of pure water, carbon dioxide, table
salt.
MIXTURE - a close combination of different matter (the parts haven’t changed)
HOMOGENEOUS MIXTURE - the same throughout. Every part is the same.
HETEROGENEOUS MIXTURE - not the same throughout. Different areas are different.
DISSOLVE - a process where something breaks down and becomes spread through
the parts of another substance and remain that way until changed.
Examples: salt dissolves in water, sugar dissolves in water.
SOLUTION - a homogeneous mixture formed when a substance dissolves in another.
Example: salt water, sugar water
SOLUTE - the substance being dissolved. Usually the smaller amount.
Example: in salt water it would be the salt
SOLVENT - the substance holding the dissolved substance. It makes the solute
dissolve. Usually the larger amount.
Example: in salt water it would be the water
SATURATED - A solution that is not able to hold any more solute (dissolved solid).
SUSPENSION - a heterogeneous mixture in which very small particles of a solid don't
dissolve but float and eventually float on top or settle on the bottom.
Example: flour in water
Mixtures are often reversible because there are ways to separate them based on the
properties of the substances.
Know these and be able to draw them:
Separating a mixture of solids
Sieving (size difference)
Wind (weight difference)
Floatation (float or sink?)
Magnetism (if one substance is attracted
to magnetic field)
Separating a mixture of solids and liquids
Evaporation
For solutions and suspensions
(takes a while and you lose the liquid)
Distillation
For solutions and suspensions
Difficult but you can recover the liquid.
Filtering
Only for suspensions. Not for solutions.
Pour through filter paper - liquid go
through, solids trapped
Decanting
Only for suspensions. Not for solutions.
Pour off top layer and leave bottom
layers.
PROPERTIES OF WATER
- Needed by all living things.
- Can exist in any state
- expands (spreads out) when it freezes.
- tiny spaces between molecules to hold other molecules. This makes it a great
solvent for solutions.
- ADHESION - molecules stick to other materials. Why tiny water droplets can sit on the
side of a glass.
- Strong COHESION - molecules like to stay together (hard to cut a drop in half.)
-strong SURFACE TENSION (caused by internal cohesion) - why water bugs can "walk
on surface". Why an over-full glass of water can bulge above edge of the
glass.
(Soap destroys surface tension)
REVERSIBLE CHANGE - a change of matter that can be put back.
Example: liquid water can be frozen to make solid ice which can be
melted to be liquid water again (still water).
IRREVERSIBLE CHANGE - A change that cannot be put back.
Example: burnt wood cannot be put back again.
PHYSICAL CHANGES OR CHEMICAL REACTIONS
PHYSICAL CHANGES
The molecules stay the same.
Examples: A piece of paper crumpled and torn up is still paper.
A glass window that is smashed is still glass molecules.
A tree that is cut down and carved into a mask is still molecules of wood.
CHEMICAL REACTIONS
Change on a molecular level. Something new created. This kind of change is
IRREVERSIBLE.
Examples: Burning a piece of paper
Baking dough into cookies.
Fireworks exploding.
FOUR signs that a chemical reaction MAY have happened:
1. Colour change
example: an iron nail rusting
2. Bubbles, fizz or foam (a gas is created)
example: mixing vinegar and baking soda
3. Energy created as heat (temperature change) or light
example: lighting a match, a glowing light stick, fireworks, explosions.
4. A precipitate - a new insoluble (doesn't dissolve) substance is formed.
(NOT same as precipitation: rain, snow, sleet or hail)
PROPERTIES OF CARBON DIOXIDE
- a gas
- part of air
- no colour
- no taste
- no smell
- does not burn (will put out a flame)
- plants need it
- animals breath it out (poisonous)
- heavier than oxygen(sinks)
- gives soda pop its fizz
- made by mixing vinegar and baking soda
Mentos in Coke is a PHYSICAL REACTION.
The carbon dioxide is already in the pop.
It’s not created.
Baking soda and vinegar is a CHEMICAL
REACTION. The carbon dioxide was not
there before. It was made when
molecules rearranged.
CRYSTALS
Some molecules like to connect in a very organized grid. In special materials, they
creates crystals as they get bigger.
Salt and sugar crystals are tiny cubes.
This happens naturally in caves with minerals.
Crystals will grow when a certain solution
(like salt water or sugar water) evaporates
and the solute (solid) reconnects.
Some things affect how big a crystal you will get:
- the more solute in the solution, the bigger the crystal.
- the slower the water evaporates, the bigger the crystal.
- a crystal grows better on a "seed" crystal (a tiny crystal to start on).
Identifying unknown powders
We can use the reactions to certain powders to identify what they are.
If we make observations in an organized way,
For instance, you perform three tests on six different powders and get the following
results:
Iodine test
Vinegar test
Water test
(No change or
(No gas or
(No change or
Type of powder
Yes it turns purple)
Yes it makes fizz)
Yes it dissolves)
Baking soda
No
Yes
Yes
Calcium carbonate
No
Yes
No
Citric acid
No
No
Yes
Baking powder
Yes
Yes
No
Talc
No
No
No
Corn starch
Yes
No
No
Each powder’s results are unique.
If you have an unknown sample of one of these powders, and you perform the tests
and get the results:
The sample doesn’t dissolve in water, it causes iodine to turn purple, but
there are no bubbles when mixed with vinegar.
Powder 1 must be corn starch.
Sometimes this information is shown in an identification key:
ACIDS AND BASES
Solutions can be an acid, they can be neutral or they can be a base a base (also
called alkaline) depending on the chemical compounds that are dissolved in it.
Acids and bases have different strengths that are measured on a pH scale which is
numbered from 0 to 14.
Pure water is at 7 and is neutral (neither acid nor base).
Acids are measured below 7 (0, 1, 2, 3, 4, 5, 6) with 0 being the strongest acid.
Bases are measured above 7 (8, 9, 10, 11, 12, 13, 14) with 14 being the strongest base.
pH indicators show a colour change to indicate if a substance is acidic or basic.
Litmus paper is a pH indicator.
There is red litmus paper and blue litmus paper.
In an ACID, red litmus paper remains red.
In a BASE , red litmus paper turns blue.
In an ACID, blue litmus paper turns red.
In a BASE , blue litmus paper remains blue.
(Remember "B" in Blue for Base)
Turns red
Turns blue
Red litmus paper
Blue litmus paper
ACID
BASE
ACID
BASE
pH paper shows colours to indicate where on pH scale a solution is (more specific).
The juice from a purple cabbage is also a pH indicator.
The juice is usually purple.
 In an ACID it turns red
 In a BASE it turns blue, and green in stronger bases, and yellow in very strong
bases.