role of sodium hydrogen carbonate in photosynthesis experiment

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What happens during photosynthesis? - OCR 21st Century Experiments to investigate photosynthesis

What is photosynthesis? Use this GCSE OCR Science study guide to revise what type of reaction photosynthesis is, as well as factors affecting enzyme action and the effect of chlorophyll on photosynthesis.

Part of Combined Science Living together - Food and ecosystems

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Experiments to investigate photosynthesis

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Greg Foot explains the effect of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis

Investigating photosynthesis

The effect of light intensity on photosynthesis can be investigated in water plants. Use Cabomba or Elodea , which are sold in aquarium shops.

The plants will release bubbles of oxygen – a product of photosynthesis – which can be counted.

A lamp with an LED bulb is set up at different distances from the plant in a test tube of water:

an LED bulb is best as this will not raise the temperature of the water
sodium hydrogencarbonate – formula NaHCO 3 – is added to the water to supply carbon dioxide – a reactant in photosynthesis – to the plant
the light intensity is inversely proportional to the square of the distance – it will decrease as the distance away from the bulb increases – so light intensity for the investigation can be varied by changing the distance from the lamp to the plant

The bubbles produced over one minute periods are recorded.

To investigate the effect of light intensity on the rate of photosynthesis.

Set up a boiling tube containing 45 cm³ of sodium hydrogen carbonate solution. Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.
Cut a piece of the pondweed, Cabomba.
Use forceps to place the pondweed in the boiling tube carefully. The pondweed should be cut end uppermost. Make sure that you don't damage the pondweed, or cause the liquid to overflow.
Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.
Calculate the mean number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
Independent variable – distance from the light source.
Dependent variable – the number of bubbles produced per minute.
Control variables – concentration of sodium hydrogen carbonate solution, temperature, using the same piece of Cabomba pondweed each time.

Care must be taken when using water near electrical equipment. Ensure that your hands are dry when handling the lamp.

Cabomba must be destroyed after use, and not released into natural water courses.

More photosynthesis occurs at higher light intensities. More bubbles of oxygen should be produced when the light is closer to the pondweed. At lower light intensities, when the light is further away, the rate of photosynthesis reduces and so fewer oxygen bubbles should be observed.

Extension activities

The volume of oxygen produced could be measured by collecting the gas produced in a gas syringe.

A diagram showing and experiment of the volume of oxygen.

The changes in the oxygen concentration in the water could be measured using datalogging equipment.

You could investigate the effect of different wavelengths close wavelength The length of a single wave, measured from one wave peak to the next. of light on photosynthesis.

Use coloured acetate filters to investigate the effects of the blue, green and red parts of the spectrum close electromagnetic spectrum The different types of electromagnetic radiation, arranged in order of frequency or wavelength. on photosynthesis.

An image showing the effect of different wavelengths of light on photosynthesis.

Photosynthesis practical

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To investigate the effect of light intensity on the rate of photosynthesis., hypothesis:, an increase in light intensity is associated with an increase in the temperature of, the leaves which in turn induces rapid transpiration and water loss..

Lamp with LED bulb -Distilled water
Sodium hydrogen carbonate solution 1% -Boiling tube
Aquatic plant -forceps
Beaker -scalpel

Risk Assessment:

Substance hazard risk control, sodium hydrogen, carbonate solution, very mild irritant may cause eye, wear goggles, 1) set up a boiling tube containing 45 cm, of sodium hydrogen carbonate, solution (1%). allow the tube to stand for a few minutes and shake to disperse, any air bubbles that may form., 2) cut a piece of the aquatic plant. the pondweed should be 8 cm long., 3) use forceps to place the pondweed in the boiling tube carefully. make, sure that you don't damage the pondweed or cause the liquid to overflow., 4) position the boiling tube so that the pondweed is 10 cm away from the, light source. allow the boiling tube to stand for five minutes. count the, number of bubbles emerging from the cut end of the stems in one minute., repeat the count five times and record your results., 5) the average number of bubbles produced per minute. repeat the experiment at, different distances away from the light source., - independent variable – distance from the light source/light intensity., - dependent variable – the number of bubbles produced per minute., - control variables – concentration of sodium hydrogen carbonate solution,, temperature, using the same piece of aquatic plant., references:, bbc bitesize: bbc.co/bitesize/guides/zs4mk2p/revision/.

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Module : Science & Materials

University : bradford college.

role of sodium hydrogen carbonate in photosynthesis experiment

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How the molar concentration of NaHCO3 (Sodium Hydrogen Carbonate) affects the rate of photosynthesis in Elodea.

How the molar concentration of NaHCO 3 (Sodium Hydrogen Carbonate) affects the rate of photosynthesis in Elodea.

In the experiment I am conducting, I will attempt to discover how the molar concentration of NaHCO 3 affects the rate of photosynthesis in Elodea by setting up simple equipment, recording the results as well as attempting to draw some conclusions from my results. I will be looking to find if a relationship/correlation exists between the concentration of NaHCO 3 and the amount of bubbles produced during a set duration.

Factor chosen:

I shall vary the molar concentration of NaHCO 3 (Sodium Hydrogen Carbonate) in order to change the concentration of available CO 2.

My variables:

In my experiment, my dependent variable will be the amount of oxygen produced, my independent variable will be the concentration of NaHCO 3 and my control variable will be light intensity/distance of lamp from Elodea as well as temperature.

Amount of oxygen produced: - the amount of oxygen produced will increase or decrease according to the strengths and amounts of the other factors. Oxygen is created as a result of photosynthesis along with glucose, and this oxygen will be present in the form of a bubble which I will attempt to count.

Concentration of NaHCO 3 :- It gives out carbon dioxide, and when it is heated at relatively high temperatures, it gives out even more carbon dioxide. The greater the concentration, the more carbon dioxide will be produced thus more oxygen will be produced as a result of photosynthesis. I will vary this variable so that I can discover if there is a proportional relationship between this and the amount of oxygen produced as a result of photosynthesis.

Light intensity:- if the light intensity is increased, the number of bubbles produced by the Elodea will also increase which is why I have to make sure that it remains constant, so as to produce more accurate results.

I will make sure that the lamp remains at the same distance from the Elodea by marking its position with a pencil. I will also make sure that the temperature remains the same by checking it from time to time and if it is above I will let it drop and if it below I will heat it to the desired level.

Prediction:

I predict that if the molar concentration of NaHCO 3 (Sodium Hydrogen Carbonate) is increased; the number of bubbles which will appear will also increase.

I further predict that if I double the molar concentration of NaHCO 3 (Sodium hydrogen carbonate) the number of bubbles will increase by approximately 25%.

Justification of prediction:

The bubbles are produced as a result of photosynthesis (oxygen is produced) and the equation for photosynthesis is:-

6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2

Carbon Dioxide + Water → Glucose + Oxygen

This is a preview of the whole essay

This equation for photosynthesis shows that carbon dioxide, water, glucose and oxygen are all related- thus if you increase one side, the other will also increase. When the molar concentration of NaHCO 3 is increased, there should be more carbon dioxide available. As a result of this, (because of the added carbon dioxide) there should be more oxygen formed, thus there should be a greater number of bubbles.

I predicted that the number of bubbles will increase by 25% when the molar concentration of NaHCO 3 is doubled, because I feel that the doubling of the molar concentration of NaHCO 3 will not result in the doubling of the amount of carbon dioxide produced thus it will not result in the doubling of oxygen produced so I predicted that it would increase by in-between 0% and 50% (25%).

Diagram of my proposed set-up:

List of apparatus:

Distilled water
Large supply of NaHCO 3
Metre ruler
Elodea/Canadian pondweed
Two measuring cylinders
Digital timer
Thermometer

Experimental procedure:

I will gather all the equipment I needed (stated above).
I will pour 100ml of 0.2M NaHCO 3 into a measuring cylinder.
I will take one branch of Elodea and place it on a white tile and cut it at a 45 o angle so that the bubbles will be able to be released into the NaHCO 3 .
Then, I will place a paper clip on the Elodea so that it stays at the same place (the water pressure is different at different heights, which may affect the rate of photosynthesis very slightly).
I will turn on the lamp and the timer simultaneously, with a thermometer placed in the solution.
I will then count the number of bubbles that appear during thirty seconds and record it down and continue to record it for three minutes whilst glancing over from time to time to check if there has been any temperature change.
Then, I will make my NaHCO 3 concentration 0.1M by removing half the amount of NaHCO 3 and adding this same amount of distilled water and stirring it (measuring the amount of water and sodium hydrogen carbonate with two separate measuring cylinders).
I will then repeat steps 3-4 for this concentration, until I have finished recording the number of bubbles that appear for all the concentrations I will use.

-I will use six different molar concentrations of NaHCO 3 (0.2M, 0.1M 0.05M, 0.025, 0.01M and 0M).

-I will record the number of bubbles that appear for three minutes instead of recording the number of bubbles for one minute, then repeating twice because there shouldn’t be much of a change as the light intensity remains constant and there isn’t much of a temperature change as I have learnt from a preliminary experiment I have done in which there was only a 0.5 0 C temperature change in three minutes. Also, I will instead of tallying the number of bubbles which appear (which I did in a preliminary experiment), I will just attempt to count the number of bubbles mentally as I discovered that it would be impossible or incredibly inaccurate to tally as well as observe the bubbles.

-With these three different readings for each concentration, I will be able to have a more accurate average. If I do have the time I will repeat my experiment and take as many readings as I can so that I can achieve more accurate results.

-I will be using a digital timer instead of a clock/watch so that the results will be more accurate.

-The possible hazards present are the possibility of contact with NaHCO 3 with the eyes or other sensitive areas. To prevent this from happening I will wear safety goggles in carrying out this experiment.

In general:

The range of my concentrations is from 0M to 0.2M, the range of the total number of bubbles produced is 0-514 and the range of the average number of bubbles produced in one minute is 0-92.8333. Mathematically, the range of the total number of bubbles is 556 and the range of the average number of bubbles produced in one minute is 92.8333 but these ranges are unreliable because the differences between the numbers are too irregular.

Analysis and conclusions:

In my experiment, I have discovered that the molar concentration of NaHCO 3 does affect the rate of photosynthesis in Elodea and that if you increase the molar concentration of NaHCO 3 the number of bubbles produced does increase as predicted with only one exception/inaccuracy present.

In the following graph, it is clear that there is a general pattern that backs up this fact (that as the concentration of NaHCO 3 is increased, the number of bubbles produced also increases). Using the table above, the existing relationship is clear with the only exception to the pattern occurring in the number of bubbles produced when using a 0.1M concentration of NaHCO 3 .

Using the table above, if you double the concentrations the increase of the number of bubbles is from, 491-502 and 484-556. This results in a 2.24% and a 14.87% increase, resulting in an average percentage increase of 8.555%. This makes my prediction at the beginning quite a way off the mark. I think my prediction was off the mark because I overestimated the amount of carbon dioxide which would be given off by NaHCO 3. Also, my results indicate that as the concentration of NaHCO 3 is increased, the rate of photosynthesis also increases resulting in more oxygen being produced, thus more bubbles.

(Percentage increase in this case = final quantity – initial quantity then multiplied by 100).

initial quantity

Evaluation:

The anomalous result could be due to human inaccuracy and lack of advanced equipment.

Additionally, at high carbon dioxide concentrations it has been noted that there may be a vigorous giving-off of gas bubbles which is actually carbon dioxide and not oxygen.

In the procedure I have used, accuracy was a problem. I feel that I measured my results as accurately as possible but doing this experiment by myself meant that it was sometimes difficult to look at the timer and check the temperature occasionally whilst attempting to count the number of bubbles which appeared all at the same time- which undoubtedly led to some of the inaccuracies of my results. Also, the task of trying to count the number of bubbles by sight was incredibly difficult considering the rapidity with which they appeared. Also, in my procedure, I did not take into account the volumes/sizes of the bubbles which could have had a considerable effect on the accuracy of my results, for instance ten large bubbles could have easily be counted as seventy small bubbles). The apparatus for measuring the volume of these bubbles (such as a micro-burette) was not available and because the experiment was conducted by me alone, I was not able to do so many things simultaneously. So in general, the accuracy of each measurement could have been improved by the assistance of others and the availability of advanced equipment.

The reliability of my results is varied. The pattern I have concluded which exists may only exist for my range of concentrations which are relatively low. Possibly, there could be a maximum number of bubbles/oxygen produced due to other limiting factors. I think that all of my results are quite reliable besides one inaccuracy which could have affected the overall accuracy of the experiment. I still feel that my results warrant some proof that there is a general pattern regarding the concentrations of sodium hydrogen carbonate and the rate of photosynthesis.

If I were to suggest any improvements, I would definitely have repeated every one of my inaccurate results (which I couldn’t do because of the lack of time) twice, I would have selected “the greenest and healthiest shoots”, and attempting to avoid storing Elodea in vessels of water which have been known to restrain photosynthesis as noted by Blackman.

Also, I would have tried using more concentrations of sodium hydrogen carbonate, especially the ones in-between the concentrations I used so that I can achieve a greater line and accuracy on my graph.

To investigate further, if it were possible I would repeat this same experiment with more advanced equipment, with several repetitions to achieve greater accuracy and with more concentrations in order to improve the conclusions I have drawn from this experiment.

Teacher Reviews

Here's what a teacher thought of this essay.

Adam Roberts

***** A well planned investigation with good justification of steps followed. Good attention to detail in the analysis /evaluation.

Document Details

Word Count 2028
Page Count 6
Subject Science

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All at once

Photosynthesis - Starch

This practical lesson covers:

The relationship between the rate of photosynthesis and A. light intensity, B. carbon dioxide, and C. chlorophyll.

Investigating factors that affect the rate of photosynthesis.

To investigate the rate of photosynthesis, the production of starch and the requirement for light, carbon dioxide and chlorophyll.

Background information:

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy, transforming carbon dioxide and water into glucose and oxygen. This practical investigates the effects of light intensity, carbon dioxide concentration, and chlorophyll presence on the rate of photosynthesis. You will measure oxygen production from pondweed as an indicator of photosynthesis and test for the presence of starch in variegated leaves to assess the role of chlorophyll.

Independent variable - Light intensity, concentration of carbon dioxide, or presence of chlorophyll.
Dependent variable - Rate of photosynthesis.
Control variables - Temperature of water, type of pondweed, duration of experiment.
Boiling tube
10 cm piece of pondweed
Light source
Test tube rack
Sodium hydrogen carbonate (varying concentrations needed including 0.2%)
Iodine solution

Method 1 - light intensity

Place the light source on the table and measure 10 cm away from the lamp. Place the test tube rack containing a boiling tube at this distance.
Add 0.2% sodium hydrogen carbonate solution to the boiling tube.
Place the pondweed into the boiling tube with the cut end at the top. Use the glass rod to push the pondweed into the boiling tube.
Leave the boiling tube to rest for 5 minutes.
Start the timer and count the number of bubbles produced in one minute.
Repeat twice and calculate a mean.
Repeat steps 1-6 for distances of (15, 20, 25, 30, 35, 40 cm) of the boiling tube from the light source.
Calculate the light intensity at each distance using the inverse square law.
Plot a graph of light intensity against the rate of photosynthesis.

Method 2 - requirement for carbon dioxide

Measure 10 cm from the light source using a ruler. Place the test tube rack containing a boiling tube at this distance.
Add sodium hydrogen carbonate solution (0.2%) to the boiling tube.
Place the cut pondweed into the boiling tube with the cut end at the top. Gently push the pondweed down with the glass rod.
Start the timer and count the number of bubbles produced in two minutes.
For each sodium hydrogen carbonate concentration, repeat the count twice more and take a mean.
Repeat steps 1-7 for 3 more concentrations of sodium hydrogen carbonate solution.
Plot a graph of the rate of photosynthesis (given by the no. of bubbles) against sodium hydrogen carbonate concentration.

Method 3 - requirement for chlorophyll

Fill a beaker with boiling water.
Submerge a variegated leaf in the boiling water for 30 seconds.
Place the leaf on a white tile so the colour change can be seen clearly.
Using a dropping pipette, add iodine solution to the leaf.
The green parts of the leaf should turn blue-black due to the presence of starch. The white areas should not.

What is the purpose of the sodium hydrogen carbonate solution in Method 1?

to measure the light intensity

to provide carbon dioxide for photosynthesis

to test the requirement for chlorophyll

to calculate the rate of photosynthesis

What is the dependent variable in Method 1?

rate of photosynthesis

concentration of sodium hydrogen carbonate

light intensity

distance of the boiling tube from the light source

What is the purpose of the iodine solution in Method 3?

To measure the light intensity

To calculate the rate of photosynthesis

To provide carbon dioxide for photosynthesis

To test the presence of starch

What is the independent variable in Method 2?

Concentration of sodium hydrogen carbonate

Distance of the boiling tube from the light source

Rate of photosynthesis

Light intensity

View Progress

Student Sheet 3 – Investigating Photosynthesis with Leaf Discs

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Age Ranges:

This SAPS teaching resource provides a fun way for students to get hands-on when investigating photosynthesis, using an easily quantifiable and reliable procedure.

Students punch out small discs from leaves, and float them in a syringe of sodium hydrogen carbonate solution. Once gas is evolved by photosynthesis, the leaf discs rise and fall.

Students can compare the rate of photosynthesis in sun and shade plants and at different light intensities, amongst many other factors. Once introduced to the basic protocol, students can easily develop their own investigations.

Suitable leaves include brassica cotyledons and fresh spinach. To compare photosynthesis in sun and shade-adapted plants, we suggest comparing pelargonium and aspidistra leaves. The leaf surface should be smooth (avoid plants with hairy leaves), and not too thick.

This resource includes teaching and technical notes, an illustrated students’ guide, and a student question sheet.