Chemical Formulae, Chemical Equations and Chemical Reactions

Whats the formulae for these common molecules:

Water

Ammonia

Carbon Dioxide

Hydrogen

Chlorine

Oxygen

H20

NH3

CO2

H2

Cl2

O2

What is a chemical equation?

A representation of a chemical reaction that uses symbols or words to show the relationship between the reactants and the products.

Give an example of a WORD and SYMBOL equation

Word = Magnesium + Oxygen --> Magnesium Oxide

Symbol = 2Mg + O2 --> 2MgO

Other than the numbers and periodic symbols, what else may you see in a chemical equation?

You may see STATE SYMBOLS which show the physical states of reactants/products.

(s) - Solid

(l) - Liquid

(g) - Gas

(aq) - Aqueous (dissolved in water)

How can you balance an equation?

You can only balance an equation by placing numbers in FRONT of the symbols, not changing the smaller numbers. You do this until theres the same number of atoms of each element on both sides of the equation.

What are the 3 signs that a chemical reaction is taking place?

1. Colour change

2. Temperature change

3. Effervescene (bubbles or fizzing)

What happens during a chemical reaction?

Chemical changes happen during a chemical reaction. This is when bonds between atoms break and they change places. The atoms from the substances in the reactants rearrange to form one or more new different substances in the products.