• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9

How light intensity affects the rate of photosynthesis.

Extracts from this document...


HOW LIGHT INTENSITY AFFECTS THE RATE OF PHOTOSYNTHESIS. Photosynthesis is the process in which plants make their own food using light. To make the food they also require Carbon Dioxide, Chlorophyll and water. This can be shown in an equation: Carbon + Water light Glucose + Oxygen. Dioxide Chlorophyll The balanced word equation for this is: 6CO2 + 6H2O C6H12O6 + 6O2 The plant takes in light energy from the sun, using the palisade cells, which are situated in the leaf. The cells contain Chlorophyll, which is the green substance inside the leaf, and also chloroplasts, which trap the sun's energy. This then reacts with the water. The plant uses light energy to separate 1 hydrogen atom from the water. This gives the OH - ion, which is hydroxyl, and the H+ ion that is hydrogen. These are then unsatisfied bonds so they join together to form 2 water molecules, 1 oxygen and 4 hydrogen molecules. (The hydrogen ions are turned into glucose), this means that the more light there is, the more water is split and hence there is more oxygen. This is all part of the light stage. The light stage involves this splitting of water and also the production of ATP, this is a source of energy which is later used in the dark stage. The light stage traps the sunlight and converts it into chemical energy. Oxygen produced in the light stage is evolved as oxygen gas, and the hydrogen reduces the carbon dioxide to carbohydrate. ...read more.


Add a spatula of sodium hydrogen carbonate to the boiling tube. 3) Place the beaker on 0cm, switch the lamp on and wait until tiny bubbles appear. When this occurs begin timing the experiment for 1 minute, record your results. 4) Move the beaker to 5cm and repeat the experiment. Keep moving the beaker up 5 cm each time. Use the stirring rod to stir the water in the beaker throughout the experiment so that the heat is evenly spread. 5) When you have a full table of results, repeat the whole experiment again so that your experiment is more accurate and work out the average. To make sure my experiment is a fair test I will keep certain things the same, I will do the experiment twice to make sure it is accurate, I will only have 1 variable throughout the experiment, this will be the distance of the light source. The temperature will be approximately 23 degrees (room temp.) because more oxygen will be produced. I will use the same piece of pondweed, the same lamp and the same amount of water each time. I will be changing the light intensity in my experiment, as this is what my investigation is based on. I will do this by moving the pondweed further away each time. In my investigation I will measure how many bubbles of oxygen are given off in one minute. ...read more.


As the plant bubbled very quickly near the start, it is possible that I did not manage to count all of the bubbles or I could have miscounted. These could all cause 1 result to be out. I could make my experiment better by making sure I used the same piece of pondweed each time, the same size, the same light - incase the 1 bulb was stronger than the other, the same amount of water each time. I could also repeat my experiment a few more times using different lengths to get more results and hence a more accurate graph. I think my experiment was good enough to give the conclusion that light intensity affects the rate of photosynthesis because my experiment was as fair as possible and I didn't make many errors. My graph also proves this because it is a curved line, which shows the light intensity, and rate of photosynthesis are proportional to one another. There are some other experiments I could carry out to extend my investigation such as, investigating the other limiting factors (carbon dioxide concentration and temperature) which affect photosynthesis rate. I could also extend the light intensity experiment by using different types of lights such as fluorescent or halogen lights. I could also investigate how different coloured pigments absorb the light more, for example black absorbs light and white reflects it, and chlorophyll is a green substance so maybe a green pigment would affect the rate of photosynthesis. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Green Plants as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Green Plants as Organisms essays

  1. How temperature affects the rate of photosynthesis.

    These stomata also provide a gateway for water to move in and out during transpiration. Each stoma (singular) is bounded by two guard cells which regulate the opening and closing of the stomata. The wall of the guard cells next to the stoma is very thick and the wall furthest from the pore is very thin.

  2. Investigating the effect of temperature on the rate of photosynthesis

    2, and the same on graph 1, where after the steepness of the curve starts to decrease. The curve peeks at around 42oC where the elodea releases an average rate of 41.2mm3/min of oxygen on graph 2. On graph 1 the curve of best fit peeks at around 42 degrees as well but with a rate of 35.4mm3/min.


    For the temperatures above room temperature i.e. 40-70C I will start with 70C degrees and work my way down. This is so that after I have heated the water, I will not have to heat it again as it will cool so I will have the required temperature.

  2. Aim: To investigate a factor that affects the rate of photosynthesis

    Conclusion: From the results that I have gathered I can state that an increase in light intensity certainly does increase the rate of photosynthesis. As was also expected in my prediction, the relationship between light intensity and the rate of photosynthesis was non-linear.

  1. An Investigation into how light intensity affects the rate of photosynthesis.

    Fair testing is very important, so the variables that are kept constant are Co2 levels. These levels will be kept the same by making sure that there is a period between the different experiments where there is not light so the plant can respire and convert the oxygen back into carbon dioxide.

  2. Find out how the amount of light, that is light intensity, affects the rate ...

    I will use a water bath- to act as a heat shield to ensure that the temperature is kept constant. Prediction: I predict that as the light level is raised the rate of photosynthesis increases steadily but only up to a certain point, but beyond that, it won't make any

  1. The aim of our investigation is to find out how the amount of light, ...

    difference because then it'll be either the temperature or the carbon dioxide level that is the limiting factor. Also with carbon dioxide it will only increase the rate of photosynthesis up to a point. If light and carbon dioxide were in plentiful supply then the factor limiting photosynthesis would be temperature.

  2. Assess how light intensity affects the rate at which photosynthesis occurs.

    Also the presence of some minerals can inhibit photosynthesis and therefore, de-ionised water which does not contain minerals must be used in order to perform an accurate experiment. * The water temperature. This must be constant for every test. It can be checked before each experiment commences using a thermometer.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work