A company claims that its new hand gel kills more bacteria than soap.
A student is given agar plates that have already been spread with a lawn of one species of bacterium, sterile paper discs, forceps, the hand gel, a soap solution, sterile water, a Bunsen burner, adhesive tape, an incubator and a ruler.
Describe a method the student could use to find out whether the hand gel kills more bacteria than the soap. In your answer you should include how the student would make this a fair test.
The student found that the clear zone around the hand gel disc was larger than the clear zone around the soap disc. Explain why this result does not prove that the hand gel is better for washing hands.
163 exam-style questions on AQA GCSE Biology 1.1 Cell structure, covering 1.1.1 Eukaryotes and prokaryotes, 1.1.2 Animal and plant cells, 1.1.3 Cell specialisation, 1.1.4 Cell differentiation, 1.1.5 Microscopy, and 1.1.6 Culturing microorganisms. Each one has a worked solution and a mark scheme showing where the marks go.