1. Chemical reactions
kathryn thumath
25/08/2019

2. What is a chemical reaction?
In a chemical reaction a new substance is always formed.
We can tell if a chemical reaction has taken place by the following changes:
Colour change
Energy change – heat, light, sound.
Solid formed – precipitate
Gas produced - efferervesence
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3. Examples of chemical reactions
A plant growing
Something burning
Baking a cake
Striking a match
Oil forming
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4. Key Words Atom - tiny particle.
Element – substance made of only one type of atom.
Compound – 2 or more elements joined together.
Mixture – substances mixed but not joined.
Reactant – something that is used up in a reaction.
Product – the new substance that is produced in a reaction
25/08/2019

5. Separating Mixtures Examples Filtering
This separates a solid from a liquid. A soluble substance from an insoluble one e.g. sand and salty water.
Distillation
This will separate a mixture of liquids that have different boiling points.
Chromatography
This will separate the mixtures of ink in a pen.
25/08/2019

6. Chemical Reactions
In a chemical reaction the reactants combine to form a new substance - the product.
Chemical equations
This is a short hand what of writing down what has happened in a reaction.
Example
Reactant + Reactant Product
Hydrogen + Oxygen Water
These are examples of word equations.
25/08/2019

7. Chemical Equations
These are short hand ways of writing down what happens in a reaction . However here we put in the Chemical Symbols for the elements and the compounds.
Example
H2 + O2 H2O
State Symbols
These tell you state a substance is in at room temperature.
S = solid, L = Liquid, G = Gas Aq. = in solution with water
25/08/2019