Matter changes state or shape but no new substance is formed
Physical change
Ice melting
Chemical change
When a chemical reaction happens and a new substance is formed
Chemical change
Rusting
Reactants
The substances used by the chemical reaction
Products
The substances produced by the chemical reaction
Chemical reaction
2 magnesium + oxygen → 2 magnesium oxide
Exothermic
A reaction that releases energy as heat
Endothermic
A reaction that absorbs energy as heat
Law of conservation of mass - Matter cannot be created or destroyed in a chemical reaction
Activation energy
The minimum amount of energy required so that a reaction can take place
Molecules can collide and bump into each other. If the molecules collide with enough energy, the bonds between the atoms can break and new bonds can form. This is how chemical reactions occur.
Energy profile diagrams
Exothermic reactions - The energy of the reactants is higher than the products, energy will be released during the reaction
Endothermic reactions - The energy of the reactants is lower than the products, energy will be absorbed during the reaction
Factors that can affect a chemical process
Surface area/size of particles
Catalysts
Temperature
Concentration of reactants
Catalyst
A chemical that speeds up a chemical reaction without being used up itself
