SE: The diagram shows the apparatus you need to set up for this experiment.
You can use any plant that grows under water. You can usually get pond weed at a pet shop, because people buy it to put into fish tanks. If you live near the sea, you can use seaweed instead.
Leave the apparatus in a place where the plant will get plenty of light. If it is very warm and sunny, you may see the gas collecting quickly. If it is colder and not so bright, you may need to leave it for a day to give time for the gas to collect.
When you have collected about half a test tube of gas, you can test it to see if it is oxygen, like this:

1) Put your hand into the water in the beaker, and hold the test tube near its opening Put your thumb over the opening, taking care to keep the test tube under water.

2) Keeping the tube open end downwards, take it out of the water.

3) Get a partner to light a wooden splint, then blow it out so that it is just glowing.

4) Now gently take off your thumb, to let the water fall out of the tube.

5) When all the water has fallen out, quickly but carefully put the glowing splint into the tube. Try not to touch the wet sides, or you will put it out!

6) If the gas is oxygen, it will make the glowing splint burst into flame.

SE: You are going to plan and carry out an experiment to investigate this question:
Is there a correlation between light intensity and the rate of photosynthesis?
A correlation is a relationship. If there is a correlation between light intensity and photosynthesis, then we would expect that changing the light intensity will result in a change in the rate of photosynthesis.

1) Write out your plan for your experiment.
Here are some ideas you can use.
• You can use a water plant like the one that you used for Activity 1.3A.
• To measure the rate of photosynthesis, you can measure how much gas the plant gives off in a certain length of time. For example, you can measure the depth of gas that collects in the test tube in one hour. For a quicker experiment, you can count how many bubbles the weed gives off in one minute. If you do that, then you don't need a funnel or test tube to collect the gas.

• To give the plant a high light intensity, you can place a lamp close to the plant. For a lower light intensity, place the lamp further away.
• Think carefully about all the variables that you must keep the same in your experiment.
• Decide whether you should do several repeats for each light intensity, so you can calculate a mean for each one.

2) Predict the results you expect to get, and explain why.

3) Check your plan with your teacher before you begin.

4) Now carry out your experiment. Make changes to your plan if you think you can improve it.

5) Record and display your results so someone else can easily understand them.

6) Write down a short conclusion to your experiment, and compare your results with your predictions.