(Things you should already know and remember) REVIEW OF SECONDARY 4 (Things you should already know and remember)

Why is the Periodic Table important to me? The periodic table is the most useful tool to a chemist. You get to use it on every test. It organizes lots of information about all the known elements. 2

The Current Periodic Table The horizontal rows are called periods. The vertical columns are called groups (families). Group 1: Alkali Metals Group 2: Earth Alkali Metals Group7 : Halogens Group 8: Inert (Noble) Gases Transition Metals: in the middle 3

PHYSICAL CHANGES Reversible Change in state: such as boiling, melting, evaportaion,… Basic identity of substance remains the same Reversible

CHEMICAL CHANGES Irreversible Basic identity of substance changes Signs of chemical change: Bubbles Precipitate forms Color change Heat or light is given off Electricity produced

DID YOU KNOW? A chemical reaction inside fireflies enables them to light up. It is called bioluminescence. Fireflies shine for a variety of reasons. It has been shown that females are more attracted to males who emit faster and more intensive flashes of light.

ELEMENTS Elements are made up of only one kind of atom, and they cannot be broken down. They are pure substances.

COMPOUNDS They are pure substances that can be broken down into simpler substances. They are made up of 2 or more elements that are chemically combined.

MIXTURES They are impure substances that are combined physically and can be separated physically. There are 2 types of mixtures: Homogeneous Heterogeneous Salt and Water Sand and Water

CHEMICAL EQUATIONS Oxygen + Hydrogen  Water (word equation) O2 (g) + H2 (g)  H2O (l ) (chemical equation) REACTANTS PRODUCTS (g) stands for gas, (l) stands for liquid, (s) stands for solid, (aq) stands for aqueous

TYPES OF CHEMICAL REACTIONS Synthesis: Combination Reaction Copper + Oxygen  Copper Oxide  Cu + O2  CuO Decomposition: Water  Hydrogen + Oxygen  H2O  H2 + O2

Synthesis General: A + B  AB Example C + O2 CO2  + O O O O O O O O

Decomposition Example: NaCl  Cl Na Cl + Na General: AB  A + B

Single displacement General: AB + C  AC + B Example: Zn + CuCl2  + +

Double displacement General: AB + CD  AD + CB Example: MgO + CaS  +

More examples Single Displacement: CuO + C  Cu + CO2 Double Displacement: BaCl2 + K2CO 3 --> BaCO3 + 2 KCl

Combustion Reactions Oxygen reacts with another substance producing carbon dioxide and water and releases heat. CH4 + 2O2 --> CO2 + 2H2O + heat

Balancing Chemical Equations Balance the following Haber Process: N2 + H2  NH3 You should have got N2 + 3H2  2NH3 This chemical reaction is named after Fritz Haber. A German chemist who found a way to combine nitrogen and hydrogen to ammonia which can be pumped directly into the soil as a fertilizer.