Chemical Reactions Summary

 

1. In a chemical reaction, new substance(s) are always formed.

 

2.A chemical reaction can be detected when one or more of the following occur;

                                COLOUR CHANGE

                           SOLID FORMED [PRECIPITATE]

                           GAS GIVEN OFF

                           HEAT GIVEN OUT

                           HEAT TAKEN IN

                           LIGHT GIVEN OUT

                           SOUND GIVEN OUT

1. An ELEMENT is a substance which cannot be broken down into anything simpler. An element is made of the same type of ATOM.

          Elements are listed in the PERIODIC TABLE.

     There are approximately 100 elements.

          Eg. Chlorine [symbol is Cl]

1. A COMPOUND is formed when 2 or more elements chemically join.

 

1. A MIXTURE is formed when 2 or more substances are simply mixed together.

 

1. Electricity is needed to break up a compound. This process is called ELECTROLYSIS.

 

1. GAS TESTS

 

   HYDROGEN; burns with a pop.

   OXYGEN; relights a glowing taper.

   CARBON DIOXIDE; turns limewater milky.

1. SPEED OF REACTIONS

   PARTICLE SIZE; the smaller the particle size the faster the    reaction.

   CONCENTRATION; the higher the concentration the faster the reaction.

1. CHEMICAL CHANGES; new substance(s) are formed.

 

     PHYSICAL CHANGES; new substance(s) are NOT formed!

     Eg. Water turning to ice or water turning to steam are CHANGES OF STATE!

1. WORD EQUATIONS

    These are used to represent a chemical reaction.

     Eg. When magnesium metal reacts with oxygen a white powder called magnesium oxide forms.

   Magnesium  + Oxygen             Magnesium oxide

Magnesium and oxygen are the REACTANTS and magnesium oxide is the PRODUCT.