4 x petri dishes
absorbent paper such as kitchen towel or blotting paper
1 molar Hydrochloric, Sulphuric and Nitric acids
Place a few layers of the absorbent paper into the petri dishes and soak each one in a different acid, with the final one containing just water.
Sprinkle 25 cress seeds onto the paper and leave for a week in a sunny location. Check the paper each day to ensure it does not dry out.
After one week count the number of seeds that have germinated in each dish and measure the height of the 10 tallest seedlings.
Goggles should always be worn when working with acids. Any spills should be cleared up straight away.