Required practical: Measure the rate of a reaction (e.g. marble chips + acid)

Aim

To investigate how surface area or concentration affects the rate of a gas-producing reaction, using initial rate or loss of mass over time.

Method (step-by-step)

1. Use excess acid with marble chips; collect gas in a syringe or measure mass loss on a balance.
2. Compare powder vs chips OR different concentrations while keeping mass of chips constant.
3. Repeat and plot gas volume vs time; draw tangent for initial rate.

Equipment

• Gas syringe or balance
• conical flask
• stopclock

Variables

• Independent: Concentration of acid or surface area of solid.
• Dependent: Initial rate (cm³ s⁻¹) or gradient of graph early on.
• Control: Temperature; mass of solid; volume of acid

Results & analysis

Higher concentration / greater surface area increases collision frequency → faster initial rate.

Graphs & interpretation

Steep start flattening as reactants are used; compare initial gradients fairly.

Exam-style question prompts

• How would you make results more reliable?
• Collision theory link

Exam tips

• Use collision theory + activation energy in explanations

Related topic revision

• Rates of reaction
• Collision theory