A student investigates the effect of sugar concentration on osmosis. Cylinders in dilute solutions are left for 20 minutes. Cylinders in concentrated solutions are left for 60 minutes.
Why is this comparison not valid?
both time and concentration can affect the measured mass change
both time and concentration determine the initial cylinder mass
changing the time prevents any water crossing the cell membranes
changing the concentration prevents any water crossing the cell membranes
41 exam-style questions on Edexcel GCSE Biology 1.4 Transport across cell membranes, covering 1.4.1 Transport into and out of cells and 1.4.2 Percentage gain and loss in osmosis. Each one has a worked solution and a mark scheme showing where the marks go.