AQA GCSE Chemistry Paper 2 Practicals

Variables

• Independent - concentration of HCl
• Dependent - temperature change
• Control - HCl and NaOH must be same amount and same temperature

Steps

1. Measure 25 cm³ of 0.25 mol/dm³ of HCl and NaOH in seperate beakers

2. Place beakers in water bath set to 25 °C until both are 25 °C

3.Add the HCl followed by the NaOH to a polysterene cup with a lid

4.Take temperature every 30 seconds and record highest temperature

5.Repeat steps 1-4 with 0.5 mol/dm³ and 1 mol/dm³ of hydrochloric acid

Variables

• Dependent - colour change
• Control - amount of liquid, person determining colour change point

Steps

• Black cross on paper placed underneath conical flask
• Add reactants
• Use timer to attempt to compare when the colour changes 

Advantages

• Can visibly see chanmge through precipitates forming and clouding the solution or the colour change

Disadvantages

• Exact point not clear as different people argue different time of colour change
• Cannot plot a rate of reaction graph

Variables

• Dependent - rate of reaction

Steps

• Place conical flask on mass balance
• Mass balance mesaures mass disappering
• Quicker reading means faster rate of reaction

Advantages

• Most accurate as mass balance is very accurate
• Rate of reaction graph can be plotted if measurements taken at regualr intervals

Disadvantages

• Gas released into room