What substance is dropped into the centre of a Petri dish of water in the diffusion experiment?
A potassium permanganate crystal.
What is the dependent variable in the potassium permanganate experiment?
How long it takes for all the water to change colour.
What independent variables could you investigate in the potassium permanganate experiment?
The temperature of the water and the size of the dish.
What indicator is used in the agar-jelly cube experiment?
Phenolphthalein.
What colour change happens to phenolphthalein in acid?
It changes from pink to clear.
What happens to the agar cube after it is left in acid for a certain time?
A certain amount of the cube will have changed colour.
What is the dependent variable in the agar-jelly cube experiment?
The percentage of the cube that has changed colour.
What independent variables could be investigated in the agar jelly experiment?
Several variables, including the surface area to volume ratio of the cube.
Why is surface area to volume ratio important in diffusion?
A larger surface area to volume ratio increases the rate of diffusion.
How do you calculate the surface area to volume ratio of a cube?
Surface area ÷ volume.
What happens to the surface area to volume ratio as the cube gets larger?
The ratio becomes smaller.
If the surface area to volume ratio is bigger, what happens to the percentage of the cube that changes colour?
A greater percentage of the cube will change colour because more of it is reached by the acid.
Do smaller or larger cubes have a bigger percentage colour change?
Smaller cubes.
How do cells in the body get the substances they need?
By diffusion through their membranes.
Why must cells be small for diffusion to work effectively?
If cells were too large, diffusion would not be fast enough to reach the centre of the cell.
