18Experimental DesignHard1 mark
A student carried out an investigation to find the effect of surface area to volume ratio on the rate of diffusion of acid into an agar block.
The student cut different-sized agar blocks containing a pH indicator and placed each agar block into different test-tubes. They recorded the time taken for each agar block to change colour completely.
Which row is correct for this investigation?
| dependent variable | variable that should be standardised during the investigation | |
|---|---|---|
| A | the size of the agar block | concentration of indicator in the agar block |
| B | time taken for the block to change colour completely | height of test-tube |
| C | the size of the agar block | time the block is in the acid |
| D | time taken for the block to change colour completely | temperature |