Hydrogen Peroxide Investigation
When hydrogen peroxide is added to a piece of fresh potato, bubbles of
gas are seen to form. When a bigger piece of potato is used, a larger
number of bubbles is produced. A possible explanation for this
observation could be that oxygen is produced when hydrogen peroxide
broken down by the enzyme catalase. A large piece of potato will
contain a higher amount of catalase than a smaller piece and therefore
produces a greater volume of oxygen.
Design an experiment to show that an increase in the concentration of
catalase affects the volume of oxygen released from hydrogen peroxide.
I predict that as you add more potato , the concentration of the
catalase increases resulting in an increase of the volume of oxygen
released from hydrogen peroxide.
Tile- to cut the potato discs
Borer (size 5)- so that the potatoes have a consistent diameter
Scalpel- to cut the potato cylinders
Ruler- to measure the size of potato discs
Beaker- to pour the hydrogen peroxide into so that it can be used
Measuring cylinder- to measure the hydrogen peroxide
5 Test tubes
(must be the same size so that the experiment is reliable)-
where the reaction will occur
Test tube rack- to put the test tubes in
Marker pen- to mark the test tubes
Gas syringe (with a rubber bung attached to it)- to measure the amount
of oxygen produced
Thermometer- to measure the temperature of hydrogen peroxide
Goggles and overall
Paper & pen- to record results
Stop watch- to control the length of time the potatoes are in the
hydrogen peroxide before taking a measurement
My independent variable is the amount of potato discs i.e. catalase
that I will use. This will be varied by adding a different number of
potato discs to each test tube. The 5 variables are 4 potato discs, 8
potato discs, 12 potato discs, 16 potato discs and 20 discs. In order
to ensure reliability in this experiment I will need to keep the other
variables constant. This includes keeping the surface area of the
potato constant- both the diameter and thickness. This will be done
by using a size 5 borer and a ruler to measure a three mm thickness.
I will use this thickness as due to my preliminary work, I know that
this size is suitable for the experiment. The same potato will also
be used for each experiment. The amount of hydrogen peroxide will
also be kept constant. This will be done by measuring 10 cm3 into a
measuring cylinder. I will use the same bottle of hydrogen peroxide
to ensure that both the concentration and the pH are the same. The
measurement of oxygen will take place after two minutes for each
reaction. Although the temperature of the hydrogen peroxide will not
be kept constant throughout the experiment, it will be monitored at
the beginning of the experiment.
The dependant variable in this experiment will be the amount of oxygen
produced. This will be measured using gas syringe (cm3) as it is
Collect all equipment needed for the experiment
Place the five test tubes into the test tube rack and label them
using the marker pen with the letters A, B, C, D and E. Check to see
that the bung on the gas syringe fits the test tubes. If it does not
then change the size of either the test tube or the bung on the gas
Pour some hydrogen peroxide into a beaker.
Measure and record the temperature of the hydrogen peroxide.
Using this hydrogen peroxide, measure 10cm3 of hydrogen peroxide using
a measuring cylinder and pour this amount into each test tube.
Using the borer, cut a sufficient amount of potato sticks for 60, 3mm
thick discs. Make sure you use the same potato for all the sticks in
order to make the test reliable.
Cut the potato sticks using the scalpel and the tile to a thickness of
3mm. Use a ruler for accuracy.
Insert 4 potato discs into test tube A and immediately insert the
rubber bung of the gas syringe into the test tube.
Start the stop watch as soon as the gas syringe is inserted into the
Shake the tube gently and observe any reaction which takes place
After 2 minutes, take the reading from the gas syringe to measure how
much oxygen gas has been formed.
Repeat steps 9-12 for test tubes B,C,D and E but with varying amounts
of potato discs. Insert 8 discs in test tube B, 12 discs in test tube
C, 16 discs in test tube D and 20 discs in test tube E.
Collect all your results in a table
Repeat the whole experiment three times, to increase its reliability.