A quick review of chapters 1-3 of unit A.

1. Unit 1 Review
Science 24

2. Chapter 1- Useful Chemistry
Chemistry Then and Now
- Farmers used to do their jobs which involved
a lot of labour. Thanks to modern chemistry,
farmers have a more efficient way to get jobs
done.
Farmers use synthetic (non-natural) chemicals
to control pests. Pesticides come in 2 types:
Herbicides kill unwanted plants, like weeds.
Insecticides kill bugs like grasshoppers, which
can devastate a crop.

3. People of the past also used to make their own soap
using ashes from fires and animal fat.
Modern chemists substitute plant oils for animal fat.
Soaps can either contain perfumes to make you smell
better, exfoliants to scrub off dead skin, or other
additives.
Soaps contain strong bases. The bases produce soap
when they react with the fatty acids in grease. One
molecule in soap dissolves in grease and another
molecule dissolves in water. This reaction enables us
to wash away grease.

4. Chemistry and Synthetics
Fabric for clothes was often taken from nature.
Examples are cotton from the cotton plant, linen from
the flax plant, wools from the coats of sheep, and
fibres from the cocoons of silk worms were made into
silk.
Chemists have produced man-made fibres to make
clothing. The first was nylon, which is made from coal,
water and air.
Examples are polyester, Gore-Tex
TM
and Kevlar.

5. Plastics, Polymers, and Alloys
Polymers are compounds that occur in nature. A
spider web and sap from rubber trees are
examples. Synthetic polymers have been created
to suit particular needs such as plastics.
Alloys are mixtures of metals that have properties
of the original metal but also have other
properties. For example, gold is a very soft metal
that would never keep its shape as jewelry. 14k
gold is an alloy made of gold, silver, and copper.

6. Chemistry at Home
We have chemicals in our houses that each has
a purpose for. We have cleaners for ovens,
floors, and etc. We have chemicals that help
clean and protect cuts like hydrogen peroxide.
We also have chemicals that, when mixed
together, can be a food source. For example,
we can add together yeast, flour, and other
things to make bread.

7. Chemistry at Work
Think of all the types of jobs out there and the
chemicals they use. Some examples are:
Automotive repair shops
Hair salons
Office work
Construction sites
WHMIS or Workplace Hazardous Material
Information System is useful information on the
store, handle and dispose of dangerous
materials that may be used at work.

8. Chapter 2- Useful Reactions
In chemical reactions, substances react to
produce new substances.
The active component in bleach reacts with
stains to make the stain colourless.
The yeast in bread reacts to create carbon
dioxide, a gas that gives the bread its airy
texture. The chlorine in swimming pools mixes
with water to create an acid to kill micro-
organisms in the pool.

9. The Changes that Occur
In a chemical reaction, the
substances that you start with are
not the same as the substances
that you end with.
This type of change cannot be
reversed.

10. Combustion is the burning of a
substance that occurs in the presence
of oxygen.
Energy is given off.
Neutralization is another chemical
reaction where an acid and a base are
combined to create a compound and
water.

11. Evidence that a Reaction has
Occurred
-a different colour is produced
-an odour, or smell, can be detected
-Bubbles appear as gas forms
-a solid, or precipitate, forms
-energy is given off in forms of light,
heat, or sound--- or absorbed

12. Energy and Chemical Reactions
Chemical changes always involve energy changes.
Some, like fireworks, are obvious
Others, like rust forming, are slow. Heat is actually
released as rust forms!!!
Exothermic- energy is released in the environment.
Endothermic- energy is absorbed and can feel cool to
the touch.

13. Chapter 3- Types of Chemical Reactions
Word equations uses words (no!) to indicate
what changed during the reaction and what is
produced.
Writing word equations has a format that never
changes.
-The left side lists all the reactants
-The right side lists all the products
-An arrow is used to show that a reaction takes
place

14. Types of Reactions
1.Simple composition- two or more elements
form a compound.
2.Simple decomposition- a compound that
breaks into its component elements.
3.Combustion- oxygen, ignition, and a fuel
source burns to produce carbon dioxide,
water vapour and energy.
4.Neutralization- an acid reacts with a base to
produce a form of salt and water.

15. Formulas for Common Compounds
Example: sulfur + zinc  zinc sulfide
The metal is named first and the non-metal
follows with an “ide” attached to the name.
Common names of compounds are often used
simply because its easier to remember.
We use the name of salt instead of sodium
chloride. Water instead of dihydrogen oxide.

16. Chemical Equations
The Law of Conservation of Mass- when a reaction
occurs, the mass of the products is always equal to
the mass of the reactants. Lavoisier determined that
none of the atoms are destroyed or lost, only
rearranged.
Chemical equations must be balanced. A balanced
chemical equation has the same elements and the
same number of atoms of each element on both
sides.
Example: Cl2 + H2  2HCl