Fiducia TogetherStandard practicals: rates
Measuring how fast a reaction goes, two standard ways.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Rate practicals measure either the disappearance of a reactant or the production of a product over time — commonly the sodium thiosulfate and hydrochloric acid cross method, or collecting gas.
Where it applies
GCSE chemistry and combined science, as required practicals.
How it works
The disappearing cross method measures the time for a mark to become invisible, so the dependent variable is time and rate is 1 over time.
Gas collection measures volume against time directly, and the gradient of the graph is the rate.
How to use it in your work
Say which quantity is measured and how rate is derived from it. 1/time is a rate; time is not.
Control variables: total volume, temperature, and the person judging the endpoint. Naming the last one is a good point.
Describe a source of error and how to reduce it.
Where to get help
Your teacher and your board's specification and mark scheme.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.