Paper 2 required practicals

RP4 - Investigate the variables that affect temperature change in chemical reactions

1. Measure a volume of acid using a measuring cylinder and pour into a polystyrene cup

2. Place the polystyrene cup inside of a beaker to make it more stable

3. Measure and record the temperature of the acid using a thermometer

4. Measure a volume of alkali using a measuring cylinder and add it to the polystyrene cup

5. Quickly put a lid on the cup and stir the solution with the thermometer through the hole of the lid

6. Once the reading on the thermometer stops changing, measure and record the temperature of the solution

7. Repeat steps 4 and 5 with different volumes of alkali

8. Repeat steps 1-7 to ensure reliability of results

9. Calculate the mean maximum temperature reached for each of the alkali volumes

Safety precautions:

• Wear goggles

• Don’t pour acid into beakers above eye height

RP5 - Investigate how changes in concentration affect the rates of reactions monitoring a change in colour or turbidity (how cloudy a mixture is).

1. Measure a volume of sodium thiosulfate using a measuring cylinder and pour it into a conical flask

2. Place the conical flask onto a printed black cross

3. Add hydrochloric acid into the conical flask

4. Swirl the solution and start a stopwatch

5. Look down through the top of the conical flask; stop the stopwatch when the solution goes turbid and you cannot see the cross (cloudy, opaque)

6. Repeat steps 1-5 using different concentrations of sodium thiosulfate solution

7. Repeat the whole experiment multiple times and calculate the mean of the results for each concentration of sodium thiosulfate solution

Problem: different people have different eyesights, so the experiment is not reproducible (able to be repeated and get the same results). Ensure to use the same size printed cross.

This shows that the greater the concentration of the chemical in the reaction, the faster the reaction takes place.

RP5 - Investigate how changes in concentration affect the rates of reactions by measuring the volume of a gas produced

magnesium + hydrochloric acid → magnesium chloride + hydrogen

1. Use a measuring cylinder to measure a volume of hydrochloric acid and place into a conical flask

2. Attatch the conical flask to a bung and delivery tube

3. Place the delivery tube into a container filled with water

4. Place an upturned measuring cylinder also filled with water over the delivery tube

5. Add a strip of magnesium to the hydrochloric acid and start the stopwatch

6. The reaction produces hydrogen gas which is trapped in the measuring cylinder

7. Measure the volume of hydrogen gas in the measuring cylinder every ten seconds until no more hydrogen gas is given off

8. Repeat steps 1-7 with different concentrations of hydrochloric acid

This shows that the greater the concentration of the chemical in the reaction, the faster the reaction takes place.

RP-6