Intermediate 1 Unit 1 b Revision Chemical Reactions

1. Intermediate 1 Unit 1 b Revision Chemical Reactions

2. Change In Appearance Sodium iodide solution and lead nitrate solution are both colourless. When they are mixed together they react and a yellow solid, lead iodide, is formed. We know a reaction has occurred because there is a change in appearance.

3. Energy Change When magnesium is placed in a bunsen flame it catches fire and burns very brightly. We know a reaction has occurred because there is an energy change, here heat and light are given out. We also see a change in appearance of the magnesium, it turns from a grey metal to a white powder, magnesium oxide.

4. It’s A Gas When Alka Seltzer is added to water it reacts and gives off a gas. We know a reaction has occurred because there is a gas given off.

5. Chemical Reactions There are three ways to tell when a reaction has taken place there is a change in appearance there is an energy change a gas is given off. When a chemical reaction takes place at least one new compound is formed.

6. Reaction Or No Reaction Try to predict what will fill the blank before you reveal it.

7. Speed Of Reactions Different reactions proceed at different rates (speed).

8. Changing Reaction Rate The rate (speed) of a reaction can be changed if we a) change the particle size of the reactants or b) change the temperature or c) change the concentration of the reactants.

9. Changing Particle Size Smaller particles react faster than larger particles. Wood shavings burn faster than wooden branches. Mince cooks quicker than casserole steak.

10. Changing Temperature The higher the temperature the faster the reaction. The exhaust system of a car rust quicker than the body because the exhaust gases are very hot. The low temperature in a fridge slows down the reaction that turns milk sour.

11. Changing Concentration The higher the concentration the fastert the reaction. Concentrated bleach kills germs faster than dilute bleach.

12. Catalysts A catalyst speeds up a reaction but does not react itself. The catalyst can be used again and again and again, etc. All cars have a catalytic converter in their exhaust system. The catalyst in the converter turns harmful gases into harmless ones. The catalytic converter works whenever the engine is running.

13. Enzymes Enzymes are biological catalysts that speed up reactions in living things.

14. Writing Word Equations When calcium is placed in water it reacts to form calcium hydroxide, hydrogen gas is also given off.

15. Writing Word Equations When calcium is placed in water it reacts to form calcium hydroxide, hydrogen gas is also given off. calcium

16. Writing Word Equations When calcium is placed in water it reacts to form calcium hydroxide, hydrogen gas is also given off. calcium + water

17. Writing Word Equations When calcium is placed in water it reacts to form calciumhydroxide, hydrogen gas is also given off. calcium + water ________> calcium hydroxide

18. Writing Word Equations When calcium is placed in water it reacts to form calcium hydroxide, hydrogen gas is also given off. calcium + water ________> calcium hydroxide + hydrogen

19. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium

20. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen

21. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen ________> magnesium oxide

22. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen ________> magnesium oxide If we heat green copper carbonate it produces black copper oxide and carbon dioxide gas.

23. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen ________> magnesium oxide If we heat green copper carbonate it produces black copper oxide and carbon dioxide gas. copper carbonate

24. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen ________> magnesium oxide If we heat green copper carbonate it produces black copper oxide and carbon dioxide gas. copper carbonate ________> copper oxide

25. Writing Word Equations When magnesium burns in oxygen a white powder called magnesium oxide is formed. magnesium + oxygen ________> magnesium oxide If we heat green copper carbonate it produces black copper oxide and carbon dioxide gas. copper carbonate ________> copper oxide + carbon dioxide