chemistry

Chemistry

Variables

Independent Variable = A variable that is being changed, such as the amount of water

given to a plant.

Dependent Variable = A variable that is being measured, such as the height of the plant.

Control Variable = A variable that is being kept the same so the experiment is not

affected, such as a type of plant used.

Elements, Compounds, and Mixtures

An element is a pure substance. All of these substances are listed in the Periodic Table. An

element cannot be broken down any further. Every element is made up of one type of

atom.

A mixture is two substances mixed.

A compound is when two or more elements are chemically bonded together.

Metals and Non-Metals

Metals are on the left, while non-metals are on the right.

Physical Properties of metals and non- metals.

Metals Non Metals

Metals NonGood conductor of electricity

• Good conductor of heat

•Poor conductor of electricity

•Poor conductor of heat

Moat metals have high melting points. Most metals are solids at 20 °C, while nonmetals

are gases and liquids.

Chemical properties of metals and non-metals.

Many metals and non-metals combine with oxygen to make oxides, such as:

Non-metal sulfur + oxygen -----> sulfur oxide

Metal magnesium + oxygen -----> magnesium oxide

Conservation of Mass

The total mass of reactants is the same as the product.

Combustion

Burning is called combustion. Combustion releases heat and light energy.

Usually, for combustion reactions, there is a fuel. When it shows

Fuel + Oxygen ------> Carbon Dioxide + Water. (Complete Combustion)

This always works when there is a full supply of oxygen. When there isn't, the examiner

usually tells us. In that situation, the word equation would look like this,

Fuel + Oxygen -------> Carbon Monoxide/Carbon + Water. (Incomplete Combustion)

•Shiny

•High density

•Malleable ( you can hammer it into

different sizes)

•Ductile (you can pull it into wires)

•Sonorous ( ringing sound when hit)

•Dull

• Low density

•Brittle (breaks easily)

•Not sonorous

Metals Non-metals

Form positive ions Form negative ions

React with acids Usually, do not react with acids

Form basic oxides Form acidic oxides

Lose electrons Gain electrons

Can corrode/rust Usually do not rust

Oxidation

Combustion is an oxidation reaction. In oxidation, the substance is gaining oxygen.

Copper + Oxygen -------> Copper Oxide. (This always works).

Testing for Hydrogen

If in a gas, hydrogen is present, you have to;

-Light a splint

-Put the splint over the gas

If the gas has hydrogen, you should hear a squeaky pop.

Testing for Carbon Dioxide

If in a gas, carbon dioxide is present, you have to ;

-You have a test tube or flask producing the gas.

-A delivery tube is attached.

-The other end of the tube is placed under limewater in another test tube or beaker.

-The gas travels through the tube.

If carbon dioxide is present, bubbles should be produced in the lime water, and the lime

water should turn cloudy.

Thermal Decomposition

Decomposition is something breaking down into simpler substances.

Thermal decomposition is something breaking down with heat.

Copper Carbonate

Green powder that breaks apart when heated

Copper carbonate → copper oxide + carbon dioxide

-It turns from green → black

-It releases a gas (carbon dioxide)

Hydrated Copper Sulfate

Blue crystals that contain water inside

Hydrated copper sulfate → anhydrous copper sulfate + water

-It turns from blue → white

-It loses water (like drying out)

So;

Carbonate = makes CO₂ gas

Hydrated = loses water

The Reactivity Series

Potassium (most reactive)

Sodium

Calcium

Magnesium

Aluminium

Carbon (not a metal, used for comparison)

Zinc

Iron

Copper

Silver

Gold (least reactive)

Displacement Reaction

If a strong metal meets a weak metal inside a compound, the strong one kicks it out.

So in a word equation,

- Spot the metal in the compound