CHEMICAL CHANGE

PHYSICAL CHANGES

 Substance looks different, but chemically still the same.  Eg. Melting, breaking.  Most physical changes are reversible. PHYSICAL CHANGES

CHEMICAL CHANGE

 New substances are formed.  Identified by:  Colour change  Light or heat produced  Precipitate formed CHEMICAL CHANGE

 To save time, we can describe a chemical reaction using equations.  Hydrochloric acid reacts with magnesium metal to produce hydrogen gas and magnesium chloride. hydrochloric acid + magnesium  hydrogen gas + magnesium chloride WORD EQUATIONS

 When writing chemical equations we start with the reactants and end with products. hydrochloric acid + magnesium  hydrogen gas + magnesium chloride  What are the reactants and products in the above word equation? CHEMICAL EQUATIONS

CHEMICAL REACTIONS

C 6 H 12 O 6 + 6O 2 --> 6CO 2 + 6H 2 O + Energy 2900kJ

 When a chemical reaction occurs, the particles of the substance rearrange themselves.  Another way to say this is that they change their chemical bonds.  The previous reaction is called ‘respiration’ and is happening in the cells of your body right now. CHEMICAL REACTIONS

 Write the word equation for respiration. CHEMICAL REACTIONS

THE WORK OF CHEMISTS

 Chemists use chemical reactions to create new substances, for example:  Materials such as fabrics, plastics and rubber.  Medicines  Food products  Or extract particular substances from others for example:  Petrol from crude oil  Metals from mineral ore THE WORK OF CHEMISTS

 You don’t have to be a chemist to make use of chemical reactions.  Some of the ways that chemistry affects our everyday lives are:  Cooking  Medicines  Air bags in cars  Special effects for movies  Fireworks  …and many, many more! USING CHEMICAL REACTIONS