Photosynthesis

Photosynthesis Investigation

to find effects of distance of a light source from pond weed has on the amount of oxygen

produced

Photosynthesis

All green plants need to be able to make their own food.They do this by a

process called photosynthesis.For photosynthesis to occur they need sunlight

energy.This energy is absorbed by a green pigment called chlorophyll,which

is mainly found in the leaves.This energy then combinEs with water molecules

(from the soil) and carbon dioxide (from the air).Then as a result of this,a

type of sugar is produced .This is called glucose.Also oxygen is made.

For my experiment I have chosen to use light distance as my variable.This

means that to carry out a fair test everything else must be kept the same

during the experiment.

Hypothesis

I think that as the light source (desk lamp) is moved closer to the

pondweed,the rate that oxygen is produced will increase therefore more

oxygen willbe produced and also more glucose. I believe this will happen

because when the the light source is nearer to the plant more of the plants

surface area is coming in to contact with the light from the desklamp

therefore more photosynthesis will occur which will mean more oxygen and

glucose will be produced.

Apparatus

• Funnel.

• Measuring cylinder.

• Stop watch.

• Card board and foil(used to fillter the light).

• Beaker.

• Desklamp.

• one metre ruler stick.

• Balance.

• Pondweed.

• Carbon dioxide Powder.

• Water.

• Scapular.

Fair Test

To ensure that a fair test is carried out the following things must be done

• The same pondweed must be used every time we change the light distance.

• Do th e experiment three times for each distance to get an accurate

average.

• There must only be one variable and that is the distance of the light

source from the plant.

• Chose a value for carbon dioxide mixture and keep at the same value allthe

way through the experiment(3 grams).

• Keep the experiment at a constant 20degres (this is because more oxygen is

produced at this temperature).

• Take results after three minutes for each induvidual experiment.

Safety

• Follow lab safety rules (eg no running bags at back etc).

• keep the desklamp away from contact with water.

• Be careful when using scapuar.

Method

• Collect apparatus.

• Set up apParatus as in diagram.

• Fill measuring cylinder and beaker with water.

• Add carbon dioxide mixture to water.

• Set up desklamp in correct position(eg 10cm).

• Turn on desklamp and start stopwatch.

• Count the bubbles for the next three minutes and also make a note of the

change in volume.

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