IGCSE Biology
Experiment Book
Name:.............................................................
Includes;
1. Investigating Osmosis
2. Enzymes – Investigating the action of the enzyme catalase
3. Food Tests – including
i.
Testing for the presence of sugar in fizzy drinks
ii.
Food Test Detective Work
4. Calculating the energy in a Peanut
5. The action of saliva on starch
6. Pathway for gases in a leaf
7. Testing a leaf for starch
8. Oxygen production during photosynthesis of an aquatic plant
9. What effects the Transpiration rate
10. Measuring the amount of oxygen in inhaled and exhaled air.
11. Effect of exercise on pulse rate
1
1. Investigating Osmosis
Method.
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You are provided with a solution of sugar of 1 mol dm-3.
You need to have 20 cm3 of this solution and also 20 cm3 of 0.5 mol dm-3, 20 cm3 of 0.1mol dm-3 sugar
and 20 cm3 of distilled water.
You are given 13 ‘chips’ made using a cork borer. Each one MUST be exactly the same length (50mm)
NB use mm, not cm. They could all be 48, 49 mm, but they MUST be the same.
Measure and record the length of each chip in the table below.
Set up 4 test tubes in a rack. Put 20 cm3 of each of the solutions into each tube, as in the table below.
Write on the tube what solution it contains and mark the level of the liquid in the tube – BEFORE
ADDING THE CHIPS
Place three ‘chips’ into each tube and note the time they go in. Keep the remaining chip in a dry testtube.
After 30 minutes, remove the chips carefully and mark the new level of the liquid in each tube.
Carefully measure the new lengths of the chips (calculate the average length of the 3 chips for each
tube) and note any difference in the texture of the chips.
Record the change in height of the liquid using + (if height increases) or – (height decreases)
1
0.5
0.1
0 (water)
Initial
Length of
Chip
(mm)
1
2
3
1
2
3
1
2
3
1
2
3
Final
Length
of Chip
(mm)
Final
Average
Sugar
Solution
(mol dm-3)
(20 cm3)
Initial
Average
Results
Average
Change in
Length of
chip (mm)
Texture of Chip
Change in
height of
solution
(mm)
1
2
3
1
2
3
1
2
3
1
2
3
Dry Test
Conclusions.
1. Using the information that you have collected explain the effects of each of these 4 solutions on the
chips.
Movement of water is due to osmosis and going from a high water potential (concentration) to a
low water potential (concentration) across a semi permeable membrane and done a water
potential gradient.
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1M sugar – has a lower water potential so the water left the potato by osmosis
0.5M sugar – has a low water potential so water also left the potato but the difference was not as
great as the 1M solution.
0.1M sugar has the same water potential as the potato so there was no net movement of water.
Water has a higher water potential than the potato so water has entered the potato by osmosis.
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2. Comment on any sources of inaccuracy in this investigation and what you could have done to rectify
them.
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Size of the potatoes – use a cork borer
Insufficient repeats - have more potato chips
Measuring the change in length – vernier callipers
Different potatoes – use the same potato.
2. Investigating the action of the enzyme Catalase
All living things make hydrogen peroxide as a waste product of cell reactions.
Hydrogen peroxide is harmful to living things so must be broken down immediately.
The enzyme called catalase speeds up this reaction.
2H2O2 ----------- 2H2O + O2
Your source of catalase is potato slices. The catalase is distributed throughout the slice but it is only the
surface catalase that catalyses the reaction.
You are going to investigate the effect of the amount of enzyme has on the reaction rate.
Method and apparatus.

Cut about 25 slices of potato (about 2-3mm thick) from a chip with a 15mm diameter. Try to cut all the
potato slices to the same size.
 Set up a test-tube in a rack and pour into it 15cm3 of H2O2.
 Put 1 square of potato in the test-tube then connect the delivery tube into the test-tube with water.
 Count the number of bubbles of gas that emerge from the delivery tube in 1 minute and record this
number.
 Repeat for one more minute and another.
 Repeat this for the other number of slices using fresh slices and hydrogen peroxide.
Results
Number of
slices
1st minute
2nd minute
3rd minute
Average per minute
1
2
4
8
10
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Plot a line graph of number of slices (x-axis) versus average number of bubbles
(5)
Conclusions.
1. Describe the relationship of the effect of the number of slices of potato on the number of bubbles
produced.
 As the potato slices increase the number of bubbles increase.
 The increase is lower when there are more potato slices.
(2)
2. Explain why it was necessary to use fresh hydrogen peroxide for each time you used different slices.
Use the terms substrate, enzyme and products.
(2)
The hydrogen peroxide is the substrate and the enzymes break it down to the products water
and oxygen. Therefore they will be less substrate available for the next experiment
3. List 2 inaccuracies in the method of this investigation and how they might have affected the results. (4)
 Different sizes of the potato slices – larger surface area for the enzymes
 Too many potatoe slices and on top of each other– so the entire surface area is not available
(use larger container
 Difficult to count the bubbles – reduced the number (video)
4. Imagine that you collected results for the 10 slices and your results were 110, 90, 70 bubbles per
minute. Would you regard these results as valid? Explain your answer.
(3)
Yes as the average is 90 but the results are far apart so I would repeat.
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3.
Food Tests
Class of
Food
Test
Carbohydrate
i.
Reducing
sugar
Put 2 cm3 of the sugar solution in the test tube
Add 2 cm3 (same volume) of Benedict’s solution
Place the test tube in a beaker of boiling water
The sugar solution and Benedict’s changes from clear blue to opaque orange.
ii.
To a few drops of starch solution add 2-3 drops of iodine solution (iodine in
potassium iodide)
Iodine colour changes from red-brown to blue-black colour.
Starch
Protein
To a 1% solution of albumen add 5cm3 dilute sodium hydroxide followed by 5cm3 of
1% copper sulphate solution (Biuret test). Shake.
A purple colour indicates a protein.
Fat
Shake 2 drops of cooking oil with 5cm3 ethanol in a dry test tube until the fat
dissolves.
Pour this solution into a test tube with a few cm3 of water.
A cloudy white emulsion will form.
i.
Testing for the presence of sugar in fizzy drinks
The presence of sugar can be tested using a reagent called Benedict’s Solution.
Equipment and Reagents
Bunsen Burner and stand, 3 test-tubes, pen, pipettes, 250 ml beakers of water, glucose solution, Fizzy
drinks (normal and lite) and Benedict’s Solution.
Method
1. Put the water in a 250 ml beaker to boil.
2. Put about 1 cm depth of the glucose, 7Up and 7Up lite in each of three test tubes.
3. Add the same depth of Benedict’s solution.
4. Label each solution.
5. Place the three test-tubes into the beaker of boiling water.
6. Observe solutions, record the colours and appearance (eg clear or cloudy or presence of a
precipitate) of the test-tubes before and after boiling, and identify 7 Up.
Results
Solution
Glucose
7 Up
7 Up Free
Colour before boiling
Colour after boiling
Conclusion
(Remember that your conclusion should just state whether reducing sugar is present/absent)
Glucose and 7up a reducing sugar was present (more in glucose). 7up free reducing sugars were
absent
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ii.
Food test detective work.
You are supplied with samples of urine from three different patients. A doctor suggests that one of these is
from a person with diabetes and one from a person with a kidney problem that lets protein into the urine.
She is not sure about the third sample. Unfortunately she did not record which sample was from which
patient.
Perform a test for Reducing sugar AND protein on EACH of the three samples.
Work as a group where 1 person does 1 test.
Record your observations and conclusions in the tables below.
(Remember that your conclusion should just state whether protein/reducing sugar is present/absent)
Benedict’s Test for reducing sugar
Urine sample
Appearance before heating
Appearance after heating
Conclusion
A
B
C
A
B
C
Biuret test for Protein
Urine sample
Appearance before test
Appearance after test
Conclusion
4.
Calculating the energy in a peanut.
The amount of energy in food is measured in kilojoules (kJ) and the old units of kilocalories. 1 calory is the
amount of energy needed to raise 1 g of water by 1 degree C.
This is the same as 4,2 Joules.
Method.
1. Collect your apparatus as shown on the diagram on the board. (Thermometer, needle, boiling tube with
25 cm3 water and holder)
2. Measure (and immediately record in the table below) the temperature of 25 cm3 of water.
3. Weigh the peanut, put it on to the mounted needle, set it alight and hold it under the boiling tube,
heating the water until the flame has burned out.
4. Measure and record the final temperature of the water, gently stirring it first.
Results
Mass of peanut =..................... g
Temperature of the 25 g of water /°C
Final temp
Starting temp
Rise in temp
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1. Calculate the amount of energy in the peanut using the formula:
Energy (Joules) = rise in temperature of the water x mass of water x 4,2
2. To convert this to kJ divide your answer by 1 000.
3. Calculate the energy value for 1 g of nut by dividing your answer to 2 by the mass of the nut.
.................................per g of nut
Draw a bar graph of the results of the whole class (just the value of the energy value/g of nut)
Conclusions:
The purpose of this part of the practical is to be critical of the method that you have used.
1. Suggest why different groups obtained different results.
There were many loses of heat for this experiment
2. What assumptions are you making about the method you used to calculate the energy content?
That all the energy was released as heat that was used to heat the water
3. Suggest 3 reasons why the method that you used could have led to errors in your results. How would
you reduce/eliminate these errors if you repeated the experiment?
 Time taken to light the peanut and start heating the water – try to be quicker
 Volume of water used – use a burette
 Wind in the classroom moved the flame so not directly under the test tube – closed environment
 Height of the flame from the peanut – maintain a constant height
 Flame too large for test tube – use a beaker
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4. Suggest how these errors would affect your results, ie under/over estimate of your calculated result.
These would all under estimate the results
5. Suggest why Nutritional Information on food labels states the amount of energy in kJ per 100g of the
food.
As this is a portion and we can compare different food groups
6. Draw a bar graph of the energy content of 5 different foods. Look at the fat/carbohydrate/protein
content of these foods and see if you can determine which class of food contains the most energy (per
g of food).
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5.
The action of saliva on starch
Saliva is produced in the salivary glands. It acts as a lubricant to allow food to be swallowed more easily. It
also contains an enzyme called salivary amylase that acts on cooked starch (a very long, insoluble
molecule) to break it down into smaller, soluble molecules of maltose.
Hypothesis: Saliva contains an enzyme that breaks down starch.
Apparatus and method.
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Collect some saliva (20 cm3 is sufficient) by chewing on a clean rubber band (this stimulates salivation)
and spitting into a small beaker.
Put the thick starch suspension into 3 test-tubes until each is about ¾ full.
Add 5 cm3 of the saliva to one tube, 5 cm3 of boiled and cooled saliva to another, and 5 cm3 of water to
the third tube. Make sure there is about 1 cm of air at the top
Mix the contents of each tube thoroughly by stirring or inverting several times and place them in a
beaker of water at 30°C.
Every 5 minutes add one drop of each mixture on to a tile and add 2 drops of iodine solution to the drop
and observe the colour. If starch is still present the iodine solution will turn black.
When the tube with unboiled saliva fails to turn the iodine solution black, pour about 1 cm depth into
another test-tube, add 1 cm depth of Benedict’s solution and place the tube into a beaker of boiling
water. Repeat this with the other 2 tubes.
Results
Contents of tube.
Starch +
Saliva
Boiled and cooled saliva
Water
Conclusions
Time /min to fail to turn iodine
black
Colour when boiled with
Benedict’s solution
1. Explain why (a) water and (b) boiled saliva were added to 2 tubes.
(a) water was used to keep the volume constant – to maintain the variable
(b) to prove it was an enzyme was acting on the substrate - control
2. Explain the colour changes in each tube after boiling with Benedict’s solution.The tube containing
saliva went orange as the amylase in the saliva had broken down the starch to maltose. The
boiled saliva stayed blue because the enzymes were denatured and the water stayed blue
because the enzymes were not present and the starch was not broken down.
3. Explain why the same depths of liquids had to be put into each tube.
To make sure the experiment was treated equally so all variables must be kept constant –
results can then be compared
4. Suggest 2 ways that you could change the method to improve on the accuracy of this investigation.
 Use equipment that is more sensitive – measure volume for both starch and Benedict’s solution
using a syringe,
 Use powdered amylase to keep the concentration constant
 Use a magnetic stirrer
 Maintain the temperature in a water bath
5. Did your results support your hypothesis? Explain your answer
Yes as the starch was broken down by the saliva as the iodine solution remained red brown
after a time.
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6.
Pathways for gases in a leaf
(a) Paint an area about 1 cm square on both the upper and lower surface of a leaf with a thin layer of clear
nail varnish and leave the varnish to dry for 10 minutes. Meanwhile, continue with instruction (b).
(b) Fill a beaker two thirds full with water (hot water if available) and heat it on a tripod and gauze over a
Bunsen burner until it reaches abt 70 °C.
(c) Extinguish the burner when the water is hot enough.
(d) Hold a leaf (not the one with the nail varnish) in forceps and plunge it into the hot water (Fig. 1), whilst
observing the lower surface of the leaf.
(e) Repeat the experiment with a fresh leaf but this time watch the upper surface.
(f) If you followed instruction (a), use fine forceps to peel the dried varnish from the lower surface, place it
on a slide and examine it under the microscope. Only a small piece of peel is needed.
(g) Count the number of stomata visible in the field of the microscope and record the results in your
notebook. If the stomata are too numerous to count over the whole field of vision, count only those in, say,
a quarter of the field or between marks on the slide. Alternatively, use a higher magnification if available.
(h) Repeat the operation with the nail varnish from the upper surface.
Discussion
1 What did you observe when the leaf was placed in hot water
while watching
(a) the lower surface, More bubbles
(b) the upper surface? Fewer bubbles
2 What was the function of the hot water in this experiment?
To break down the cells
3 Judging from your varnish peels, which surface of the leaf had
the greater number of stomata? Lower
4 Use your results and your knowledge of leaf anatomy to explain
your observations in this experiment.
There are more stomata on the bottom of the leaf because
they have to be open to allow gas exchange to occur (CO2 in
O2 out) consequently water is lost from the leaf through
diffusion as transpiration. The bottom of the leaf is in the
shade and therefore less sunlight reaches this area and less
transpiration occurs
Prepared by C. Coetzer Jan 2013 (edited Nov 2014)
Fig. 1
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7. Testing a leaf for starch
Equipment and Materials
250 cm3 beaker;
Tripod & gauze;
Bunsen Burner;
Test Tube;
Water;
Forceps;
Methylated Spirits;
Petri dish Lid;
Iodine Solution;
Dropping Pipette
Flammable Liquid
Boiling Alcohol
Leaf
Hot Water
Bunsen OUT
Extracting chlorophyll from a leaf
Method
1. Half fill a beaker (250 cm3) with water and place it on a tripod over a Bunsen burner.
2. Heat the water till it boils and then turn down the Bunsen flame sufficiently to keep the water at boiling
point.
3. Hold the leaf in forceps and plunge it into the boiling water for 5 seconds. This will kill the cells, arrest all
chemical reactions and make the leaf permeable to alcohol and iodine solution later on.
4. TURN OUT THE BUNSEN BURNER.
5. With the forceps, push the leaf carefully to the bottom of a test-tube and cover it with methylated spirit.
6. Place the test-tube in the hot water bath and leave it for 5 minutes. The alcohol will boil and dissolve out
the chlorophyll in the leaf.
7. Use a test-tube holder to remove the test-tube from the water bath and tip the green alcoholic solution
into the receptacle for waste alcohol but take care not to tip the leaf out as well.
8. If the leaf is white or very pale green, go on to (9). If there is still a good deal of chlorophyll left in the
leaf, boil it for a further 5 minutes with a fresh supply of alcohol, using the hot water bath. If it is
necessary to relight the Bunsen to heat the water to boiling point, remove the test-tube and do not
replace it until the Bunsen flame is extinguished.
9. Fill the test-tube with cold water and the leaf will probably float to the top.
10. Use forceps to place the leaf on the back of a Petri dish lid and, holding the leaf stalk firmly against the
lid, let a fine trickle of water from the cold tap run over it to wash away the alcohol.
11. If necessary, use the forceps to spread the leaf quite flat on the lid. Using a dropping pipette cover the
leaf with iodine solution for one minute.
12. Take the leaf to the sink and holding it on the lid, wash away the iodine solution with a fine trickle of cold
water.
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Results and Discussion
1. What is the reason for extracting the chlorophyll from the leaf?
So the colour change with the iodine solution can be seen
2. For what substance is iodine a test? What result do you see if this substance is present?
Starch – blue-black colour
3. What was the colour of the leaf;
(a) Immediately before adding iodine? white
(b) After adding iodine? Blue- black
4. How do you interpret this change? Starch is present
5. What products of photosynthesis might be present which are not revealed by this test?
Oxygen and glucose
Conclusion
Where chlorophyll is present in the leaf cells phosynthesis is occurring and glucose is made into
starch.
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8. Oxygen production during photosynthesis of an aquatic plant
Some pupils did an investigation of the effect of temperature on the rate of photosynthesis in a sample of a
freshwater plant, using the apparatus you have seen in class.
Results
Temperature /°C
10
15
20
30
40
6
9
13
25
42
Bubbles min-1
7
5
8
8
12
14
20
22
39
55
Mean of 3 replicates (nearest whole number)
Plot a line graph of the results use the mean of each temperature
Conclusions
1. Explain why the plant had to be kept in tap water with added sodium hydrogen carbonate. (Think about
the raw ingredients for photosynthesis)
(2)
Carbon dioxide and water are necessary for photosynthesis
2. How do aquatic plants obtain their raw ingredients for photosynthesis?
From the water through the stomata
(2)
3. Name the (a) independent variable and (b) the dependent variable in this investigation.
a) temperature
b) number of oxygen bubbles
(2)
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4. Write a sentence to describe the relationship between the temperature of the water and the rate of
photosynthesis.
(2)
The higher the temperature the more oxygen bubbles produced.
5. Use your graph to identify the rate if photosynthesis at (a) 25° and (b) 35°.
(a) 25°..............................................
(b) 35°..............................................
(4)
6. (a)Which of these results looks anomalous (does not fit into a pattern)?
40o 55 bubbles
(b) Suggest what the value should be and suggest why this result could have been strange.
37 – 44 bubbles
(c) What should the person do in order to check this value?
Repeat the experiment
(4)
7. List the factors that had to be kept constant in this investigation.
(2)
Carbon dioxide concentration,
Water volume
Light intensity
Light duration
9.
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Potometer Practical
Four potometers were set up in different environmental conditions during daylight.
The length of the water column was measured at regular intervals.
The results are shown in the table below.
‘Still’ means the air is not moving.
Environmental
condition
10O, still, humid
25O, still, dry
25O windy, dry
10O,still, dry
0 min
150
150
150
150
30 min
150
130
125
140
Length of water column /mm
60 min
90 min
120 min
150
150
150
120
95
75
110
90
45
125
missing
100
150 min
150
50
15
90
Plot four lines of these results on ONE set of axes, time on the x-axis, length of water column on the yaxis.
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Conclusions
1. Which set of conditions gave the fastest water uptake?
25o windy and dry
(1)
2. Calculate the average rate of water uptake during this experiment, for the plant in question 1. This can
be calculated by dividing the volume of water taken over the entire period by the time taken, in minutes.
Show your working out.
(3)
-1
150 – 15 = 135mm / 150 min = 0.9 mm min
3. Explain why these conditions gave the fastest rate.
The transpiration rate is increased because;
High temperatures increase the kinetic energy of the molecules of water,
Dry and windy conditions increase the water potential gradient that increases the rate of
transpiration
(3)
4. Use your graph to determine the likely value of the ‘missing’ data.
Indicate on the graph how you determined this figure.
Draw lines on the graph from the x axis time to the y axis height
5. List THREE factors that should be kept the same to make this a fair test.
The type of plant
The number of leaves
The carbon dioxide concentration
The light intensity
The light duration
(3)
6. Explain why these figures measure the rate of water uptake and not transpiration rate.
Water is used by the plant for;
Photosynthesis,
Keeping the cells turgid
Used in chemical reactions
(2)
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10. Measuring the amount of oxygen in inhaled and exhaled air.
Theory
Oxygen is necessary for fire to burn and the test for oxygen in chemistry is re-lighting a glowing splint.
Since the air we breathe contains 21% oxygen and the air that we breathe out contains 16% oxygen we
can test for presence of oxygen in our inhaled and exhaled air.
Materials
Glass jar with lid, deflagrating spoon, candle, lighter, timer, 1m tube, bowl (washing up size), water.
Method
1. The candle on the deflagrating spoon is lit and dropped into a glass jar.
2. Time is measured until the flame is extinguished.
3. The experiment is repeated twice more.
4. The glass jar is filled with water and turned upside down in a large bowl of water.
5. Exhaled air is collected in the jar through the tube and the lid is placed on the jar while it is underwater.
6. The covered jar is moved to the side.
7. Steps 1- 3 are repeated.
Diagram
Results
Conclusion
The air we inhale contains 21% oxygen and the air we exhale contains 16% oxygen. The body
uses about 25% of the oxygen available in the atmospheric inhaled air.
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11. The affect of exercise on pulse rate.
The practical will test the time for the pulse rate to return to normal. Work in teams of two.
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Predict the effect and write a hypothesis
.....................................................................................................................................................................
.....................................................................................................................................................................
Method
One team member to take their own pulse rate for 30s. Tell partner they will double it for a pulse rate
and fill in column 1.
Students to step up on a chair for 3 minutes. Important for another student to hold the chair.
The student takes own pulse rate after exercise (again for 30s tells partner they double it and records
in column 2).
Straight away start counting beats for another 30s (Tell partner to double it and record in column 3)
Continuously take pulse rate for 30s until it returns to normal or levels out.
Record the results from the entire class on the board.
Results
1
Student Pulse
Before
Exercise

2
Pulse After
180
seconds of
Exercise
3
Pulse After
60
seconds of
Resting
4
Pulse After
90
seconds of
Resting
5
Pulse After
120
seconds of
Resting
6
Pulse After
180
seconds of
Resting
7
Pulse After
210
seconds of
Resting
Plot a line graph of the pulse rates of a selection of students with time on the x axis and pulse rate on
the y axis.
Prepared by C. Coetzer Jan 2013 (edited Nov 2014)
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