The document describes an experiment that investigates how temperature affects the rate of diffusion of pigments from beetroot cells into water. The hypothesis is that increasing the temperature will increase the rate of diffusion, causing the water to appear darker. Beetroot discs will be placed in water baths at different temperatures, and a colorimeter will measure the darkness of the water over time to test this. The independent variable is the temperature, which will be varied between 5°C, 20°C, 35°C, 45°C and 55°C. The dependent variable is the darkness of the water, which will be measured using a colorimeter.

1. Diffusion in beetroot
Introduction
Beetroot (Beta vulgaris) is a plant that has a distinctive purple colour. This colour is caused by
pigments called betacyanins found inside the large vacuole of the plant cell. The pigment can
diffuse out of the cells quite easily and stain the skin etc. of people using it.
We are going to investigate whether the rate of diffusion of the pigment is affected by the
temperature. To do this we will put discs of beetroot into boiling tubes full of water at different
temperatures. Diffusion is the movement of particles from an area of higher concentration (in
this case inside the beetroot cells) to an area of lower concentration (the water surrounding the
beetroot). We can see how much diffusion has happened by looking at how dark the water is at
the end of the experiment.
Hypothesis
I think that as the temperature is increased the rate of diffusion should increase too because the
pigment particles will have more energy and therefore move about more. The faster they move
the faster they should be able to diffuse out of the cells. The darker the colour of the water at
the end of the experiment the more diffusion there has been. Therefore I predict that the higher
the temperature the darker the colour of the water will be.
Method
1) Measure 20ml of water into each of 5 boiling tubes.
2) Place 1 boiling tube into a water bath at the following temperatures; 35 °C, 45 °C , 55 °C
place one into the ice bath at around 5 °C and leave one on your bench (room temperature
= 20 °C). (Why do you need to heat the water FIRST before you do anything
else?)

2. 3) Use a cork borer to take a cylinder of beetroot tissue from one of the beetroot halves.
(Which variable is this helping us to control?)
4) Use your knife and white tile to cut 25 discs of beetroot, each with a thickness of about
0.5 cm
5) Put 5 discs of beetroot into each tube and start timing.
6) After 15 minutes take the tubes out of the water bath and put a small sample of each into a
cuvette. Make sure the cuvette is clean and dry (Why is it important not to write or
stick labels onto the cuvette? )
7) Use a cuvette of pure water to calibrate the colorimeter (why is this step important?)
8) Place each sample in the colorimeter and record the % of light that travels through the
solution. (what does it tell you about the colour of the solution if the
transmission is HIGH?)
Variables
The independent variable is_________________________________________________
I will change this variable by __________________________________________________
_________________________________________________________________________
The values I will use for this variable are;________________________________________
The dependent variable is __________________________________________________
I will measure this variable accurately by ________________________________________
_________________________________________________________________________
There are at least 4 control variables in this experiment. For each one you think of say WHAT it
is and HOW you will make sure that it is controlled.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________

3. _________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
Change to the method
There may be something that you think you need to change in the method. You need so say
what you changed and WHY you thought this would make the experiment better.
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________________________________________
_____________________________________________________
Record your results in this space.