1. 1. Recognising a Reaction
Chemical Reactions
1. Recognising a Reaction
LO: I understand what a chemical reaction is.

2. A match burning (YES)

3. Making toast (YES)

4. Ice melting (NO)

5. Glass breaking (NO)

6. Salt dissolving (NO)

7. A roof rusting (YES)

8. Frying an egg (YES)

9. Paint drying (NO)

10. Bananas rotting (YES)

11. Water boiling (NO)

12. An explosion (YES)

13. Making a cake (YES)

14. Glue drying (NO)

15. Iron melting (No)

16. Adding milk to tea (NO)

17. Germinating seeds (YES)

18. Mouldy bread (YES)

19. When a chemical reaction takes place a . substance is always formed.
new
Examples of chemical reactions: C
ooking B
urning
C (rusting)
orrosion G
rowing D
ecaying
LO: I understand what a chemical reaction is.

20. If a new substance isn’t made then a change has happened.
physical
Examples of physical changes: M
elting F
reezing C
ondensing
B /e
oiling
vaporating D
issolving B
reaking
LO: I understand what a chemical reaction is.

21. 2. Evidence for a Chemical Reaction
LO: I know some indicators of a chemical reaction.

22. + (a) Change in Appearance Aim:
To show that a change in appearance can occur during a chemical reaction.
Diagram:
filter paper
potassium iodide
lead
nitrate
filter funnel +
LO: I know some indicators of a chemical reaction.

23. 2. One solution was poured into the other.
Method:
1. Potassium iodide solution and lead nitrate solution was added to separate test tubes.
2. One solution was poured into the other.
3. The mixture was filtered.
Result:
A yellow solid was produced.
Conclusion:
During the reaction the two colourless solutions changed appearance to give a yellow solid.
LO: I know some indicators of a chemical reaction.

24. copper sulphate solution
(b) Change in Energy
Aim:
To show that some chemical reactions can produce a change in temperature.
Diagram:
thermometer
iron
copper sulphate solution
LO: I know some indicators of a chemical reaction.

25. 1. The temperature of the copper sulphate solution was measured.
Method:
1. The temperature of the copper sulphate solution was measured.
2. Two spatulas of iron filings were added to the boiling tube and stirred.
3. The highest temperature reached was measured.
Result:
Start Temperature =
Final Temperature =
Temperature Rise =
Conclusion:
During the reaction the temperature increased due to heat energy being produced.
LO: I know some indicators of a chemical reaction.

26. Change in Energy (continued)
Aim:
To show that some chemical reactions can produce light energy.
Diagram:
magnesium
Bunsen
LO: I know some indicators of a chemical reaction.

27. 2. The magnesium was pulled out of the flame once it caught fire.
Method:
1. A small strip of magnesium was held in a Bunsen flame at the tip of the cone.
2. The magnesium was pulled out of the flame once it caught fire.
Result:
The magnesium burned with a bright white light.
Conclusion:
The bright white light during the reaction shows that light energy was produced.
LO: I know some indicators of a chemical reaction.

28. A change in appearance ( change) colour
Summary
During a chemical reaction some of the following may be seen (observed):
A change in appearance ( change)
colour
A change in energy ( , or )
heat
light
sound
A new substance is formed ( or )
solid
gas
LO: I know some indicators of a chemical reaction.

29. 3. Chemical Equations
LO: I know how to write a chemical equation.

30. A chemical equation is a short way of writing what happens during a chemical reaction.
For example:
Magnesium burns in oxygen to produce magnesium oxide.
Equation:
magnesium oxide +
magnesium
oxygen
reactants
product
(always on the left)
(always on the right)
LO: I know how to write a chemical equation.

31. + + + + + Examples: zinc oxygen zinc oxide
Zinc metals reacts with oxygen to produce zinc oxide.
hydrogen
chlorine +
hydrogen chloride
Hydrogen gas reacts with chlorine gas to produce hydrogen chloride gas.
copper sulphate
iron +
iron sulphate
copper
Copper sulphate reacts with iron to produce iron sulphate and copper.
potassium iodide
lead nitrate +
lead iodide
potassium nitrate
Potassium iodide and lead nitrate solutions react to produce lead iodide and potassium nitrate.
methane
oxygen +
carbon dioxide
water
Methane gas reacts with oxygen to produce carbon dioxide and water.
LO: I know how to write a chemical equation.

32. 4. Speed of Reactions
LO: I know how to change the speed of a chemical reaction.

33. potassium permanganate
(a) Change in Particle Size
Aim:
To show the effect of changing the particle size on the speed of a reaction.
Diagram:
potassium permanganate
rhubarb
1 piece
8 pieces
(large particles)
(small particles)
LO: I know how particle size affects the speed of reaction.

34. 1. 50cm3 of potassium permanganate was added to two beakers.
Method:
1. 50cm3 of potassium permanganate was added to two beakers.
2. A piece of rhubarb was added to one beaker.
3. An identical piece of rhubarb was chopped into 8 pieces and added to the other beaker.
4. Both beakers were stirred.
Result:
The beaker with the small pieces went colourless first.
Conclusion:
The smaller the particle size, the faster the speed of the reaction.
LO: I know how particle size affects the speed of a reaction.

35. Potatoes cook when cut up into smaller pieces.
Everyday examples:
faster
Potatoes cook when cut up into smaller pieces.
slower
A block of wood burns than wood shavings.
explosive
Coal dust is whereas a lump isn’t.
burn
Steel wool can but a steel nail can’t.
LO: I know how particle size affects the speed of a reaction.

36. + (b) Change in Temperature Aim:
To show the effect of changing the temperature on the speed of a reaction.
Diagram:
Solution A
Solution B
measuring cylinder +
LO: I know how temperature affects the speed of reaction.

37. 1. 25cm3 of solution B was added to 25cm3 of solution A in a beaker.
Method:
1. 25cm3 of solution B was added to 25cm3 of solution A in a beaker.
2. The time taken for the blue/black colour to appear was measured.
3. The temperature was recorded.
4. Steps 1 to 3 were repeated except solution A was heated to 40˚C first.
Result:
Temperature (˚C)
Time Taken (s)
Conclusion:
The higher the temperature, the faster the speed of the reaction.
LO: I know how temperature affects the speed of a reaction.

38. A car exhaust rusts than the rest of the car.
Examples:
faster
A car exhaust rusts than the rest of the car.
slower
Food goes off in the fridge and even
in the freezer.
slower
slower
Biological washing powder works in cold water than in warm water.
faster
Plants grow in a greenhouse than outside.
LO: I know how temperature affects the speed of a reaction.

39. (c) Change in Concentration
The number of particles in a particular volume of gas or liquid is known as the concentration.
Low concentration
High concentration
(dilute)
(concentrated)
The concentration of a solution is usually written on the bottle, eg, 1M or 0.1M.
LO: I know what is meant by concentration.

40. Aim:
To show the effect of changing the concentration on the speed of a reaction.
Diagram:
carbon dioxide
fill line
water
hydrochloric acid
marble chips
LO: I know how concentration affects the speed of a reaction.

41. 1. The apparatus was set up as shown.
Method:
1. The apparatus was set up as shown.
2. 10cm3 of 0.5M acid was added to 4 pieces of marble.
3. The time taken for the gas to fill to the line was measured.
4. Steps 1 and 2 were repeated using 1M and 1.5M acid.
Result:
Concentration
Time Taken (s)
LO: I know how concentration affects the speed of a reaction.

42. The higher the concentration, the faster the speed of the reaction.
Graph:
Time (s)
Concentration (M)
Conclusion:
The higher the concentration, the faster the speed of the reaction.
LO: I know how concentration affects the speed of a reaction.

43. Plants grow when carbon dioxide is added to the air in the greenhouse.
Examples:
faster
Ships rust at sea than on a river because of the higher concentration of salt.
slower
Statues corrode in the country than the city because of the lower concentration of acid rain.
faster
Plants grow when carbon dioxide is added to the air in the greenhouse.
hotter
Fires burn when air (oxygen) is blown on them.
LO: I know how concentration affects the speed of a reaction.

44. To show the effect of adding a catalyst on the speed of a reaction.
(d) Catalysts
Aim:
To show the effect of adding a catalyst on the speed of a reaction.
Diagram:
Before
After
LO: I know how catalysts affect the speed of a reaction.

45. 1. 25cm3 of solution A was added to 25cm3 of solution B in a beaker.
Method:
1. 25cm3 of solution A was added to 25cm3 of solution B in a beaker.
2. The mixture was heated to 50˚C.
3. 10cm3 of the catalyst was added.
Result:
The mixture was pink at the beginning, then green with lots of bubbles and back to pink at the end of the reaction.
Conclusion:
A catalyst speeds up a reaction without being used up itself.
LO: I know how temperature affects the speed of a reaction.

46. Some washing powders use biological catalysts to remove from clothing.
Examples:
exhausts
Catalytic convertors in car change harmful gases into less harmful ones.
Some washing powders use biological catalysts to remove from clothing.
stains
LO: I know how catalysts affect the speed of a reaction.

47. The speed of a chemical reaction can be increased by:
Summary
The speed of a chemical reaction can be increased by:
the particle size.
decreasing
the temperature.
increasing
the concentration.
increasing
adding a
catalyst
LO: I know how to change the speed of a chemical reaction.