1. Place cotton wool and a cress seedling with well-developed roots in a boiling tube that is approximately half full with water.
SAFETY • Do not ingest copper sulfate.
2. Stand the boiling tube in a test tube rack. Use a dropper to slowly trickle vegetable oil down the side of the boiling tube so it forms a layer on top of the water.
3. Place a small plastic bag over the top of the boiling tube to cover the leaves fully. 4. Secure the bag in place with an elastic band to form a gas-tight seal.
5. Leave the seedling on a windowsill for 72 hours. Observe the inside of the bag for droplets of liquid.
6. Using a different dropper, remove some of the liquid that has formed on the inside of the bag and drop it onto a weigh boat containing white anhydrous copper sulfate.
7. Observe and record any colour change in the copper sulfate. Plastic bag
Water Test tube rack Dropper
Vegetable oil Plastic bag Elastic band
Weigh boat
White anhydrous copper sulfate
Elastic band
Boiling tube Water Oil Cress seedling
)Fig. 37.5 To investigate transpiration in plants
Cotton wool j Go to page 110 of your Experimental Investigations Log to write up this investigation.