Question 7
Aim: To investigate the gas produced during photosynthesis. Materials: Large beaker, test tube, filter funnel, small blocks, water (preferably pond water), freshwater plant (such as elodea, cabomba or hydrilla), stopper, splint, lighter or a box of matches, safety goggles.
1 Work in pairs. Set up the experiment as shown.
2 Leave the set-up in a well-lit area for at least one day.
3 When plenty of gas has been collected in the test tube, carefully remove the tube from the top of the funnel. Make sure to keep the mouth of the test tube under water so that no gas may escape.
4 With the tube still upside down, use your thumb to cover the mouth of the test tube to ensure that no water or gas escapes. Keep the test tube in this position as you remove it from the water.
5 Remove your thumb carefully to create a small opening for the water to run out while keeping the gas inside.
6 Use a stopper to cover the mouth of the test tube. Place the test tube, the right way up, in a test-tube rack.
7 Light a splint and then blow it out. Ensure that it is still glowing but not burning.
8 Take the stopper out of the test tube and hold the splint near the mouth of the test tube.
9 Record what happens to the glowing splint.
Caution: Put on safety goggles when carrying out the splint-test step.
1 Work in pairs. Set up the experiment as shown.
2 Leave the set-up in a well-lit area for at least one day.
3 When plenty of gas has been collected in the test tube, carefully remove the tube from the top of the funnel. Make sure to keep the mouth of the test tube under water so that no gas may escape.
4 With the tube still upside down, use your thumb to cover the mouth of the test tube to ensure that no water or gas escapes. Keep the test tube in this position as you remove it from the water.
5 Remove your thumb carefully to create a small opening for the water to run out while keeping the gas inside.
6 Use a stopper to cover the mouth of the test tube. Place the test tube, the right way up, in a test-tube rack.
7 Light a splint and then blow it out. Ensure that it is still glowing but not burning.
8 Take the stopper out of the test tube and hold the splint near the mouth of the test tube.
9 Record what happens to the glowing splint.
Caution: Put on safety goggles when carrying out the splint-test step.
