Worksheet: Investigating Photosynthesis

In this worksheet, we will practice describing practical experiments that can be used to investigate the effect of limiting factors on the rate of photosynthesis.

Q1:

The following equation shows the relationship between the distance of a light source and the light intensity: lightintensitydistance1.

If the distance between the plant and the light source halves, what happens to the rate of photosynthesis?

  • ANo change occurs.
  • BIt quadruples.
  • CIt halves.
  • DIt triples.

Q2:

What gas is produced by plants when they photosynthesize?

  • ACarbon dioxide
  • BOxygen

Q3:

The diagram provided shows the experimental setup for investigating the effect of light intensity on the rate of photosynthesis in algal balls.

Equal numbers of algal balls are added to 50 cm3 of hydrogencarbonate indicator solution and covered with lids.

As the concentration of CO2 increases in the solution, the solution turns more yellow.

As the concentration of CO2 decreases in the solution, the solution turns more purple.

Which of the following correctly describes the relationship between CO2 concentration and the rate of photosynthesis?

  • AThe more the algal balls photosynthesize, the more CO2will be in the hydrogencarbonate solution.
  • BThere is no link between the rate of photosynthesis and CO2 in the hydrogencarbonate solution.
  • CThe less the algal balls photosynthesize, the less CO2 will be in the surrounding atmosphere.
  • DThe more the algal balls photosynthesize, the less CO2 will be in the hydrogencarbonate solution.

In which of the 5 bottles will photosynthesis be happening the fastest?

Which of the 5 bottles will contain the greatest amount of CO2 remaining in the solution?

Q4:

The diagram shows a simple set of the equipment used to investigate the effect of light intensity on the rate of photosynthesis in pondweed.

Using this equipment, how can the rate of photosynthesis be measured?

  • ADistancenumberofbubblesproduced÷
  • BNumberofbubblesproduceddistance÷
  • CDistancetime÷
  • DNumberofbubblesproducedtime÷

In this experiment, what is the independent variable?

  • ATemperature of water
  • BBubbles produced
  • CLight intensity
  • DCarbon dioxide concentration

Q5:

When it is not needed by the plant, the glucose made in photosynthesis can be stored as starch. Iodine can be used to test a leaf for the presence of starch in a process outlined in the diagram provided.

In step 2, why is the leaf boiled in ethanol?

  • ATo break down the nuclear membrane
  • BTo break down the cell walls
  • CTo make the leaf less reactive
  • DTo remove the green pigment

What color will the iodine turn into if starch is present in the leaf?

  • ABrick red
  • BBrown
  • CBlue/black
  • DDark green

Q6:

When investigating the effect of light intensity on the rate of photosynthesis, a vial or beaker of water is often placed in between the lamp and the plant, as shown in the diagram. Which of the following best explains why?

  • ATo replicate the effect of natural sunlight more closely
  • BTo absorb the heat from the lamp so the light intensity is the only variable that changes
  • CTo absorb the light from the lamp so it is always kept constant
  • DTo ensure the light intensity does not get too high and denature the enzymes needed for photosynthesis
  • ETo prevent the plant from being influenced by other sources of light

Q7:

To calculate light intensity, the following equation can be used: 𝐼=𝐼×𝑑𝑑neworiginaloriginalnew

The plant starts 1 cm away from the light, which is emitting 1 lux of light.

The light is turned on and the plant is moved to be 5 cm away from the light source. What is the new light intensity?

Q8:

The table provided shows an example set of results for a student’s investigation into the effect of light intensity on the rate of photosynthesis. The student timed how long it took a plant to release 10 bubbles at each light intensity.

Relative Light IntensityTime (s)Relative Rate of Photosynthesis (s−1)
0.480.1250
0.3320.0313
0.258
0.11010.0099

Calculate the missing value using the following equation: relativerateofreactiontime=1÷. Give your answer to 4 decimal places.

Q9:

The inverse square law provided can be used to calculate light intensity using the distance a light source is from an object (𝐼=lightintensity, 𝑑=distance). 𝐼=𝐼×𝑑𝑑neworiginaloriginalnew

If the new light intensity is 800 lux when the light source is at a distance of 12 centimeters, what was the original light intensity when the light source was 6 centimeters away?

Q10:

The inverse square law provided can be used to calculate light intensity, using the distance a light source is from an object (𝐼=lightintensity, 𝑑=distance). 𝐼=𝐼×𝑑𝑑neworiginaloriginalnew

If the original light intensity is 500 lux when the light source is at a distance of 10 centimeters, what is the new light intensity when the light source is moved to 5 centimeters away from the object?

  • A1,000 lux
  • B200 lux
  • C2,000 lux
  • D10,000 lux

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