3} the area over which diffusion takes place. The larger the surface area then the more molecules or ions can travel at any one time, therefore the faster the rate of diffusion.
4} Variations in the cells membrane may affect diffusion as well. Diffusion takes place across epithelial layers or cell membranes. For example the greater the number and size of pores in cell membranes the greater the rate of diffusion.
5) The nature of the molecules or ions. Large molecules require more energy to get them moving than small ones. Large molecules diffuse more slowly than smaller molecules. Non-polar molecules diffuse more easily than polar ones. An example of a non-polar molecule would be water and a polar molecule would be a substance such as ethanol.
6) Temperature, at high temperatures, molecules and so has much more kinetic energy than at low temperatures. They move around faster and thus diffusion takes place faster.
In this particular investigation the experiment will be observing the effects of temperature on the rate of diffusion.
The beetroot plant is a eukaryotes cell. It contains a partially permeable membrane, which controls the exchange of the cell and its environment. The membrane is an extremely thin layer (8-10 nanometers nm) thick. It contains mostly lipids and proteins. The lipids found in cell membranes belong to a group known as triglycerides. The triglycerides again belong to the subgroup called phosolipid layer bialayer.
Inside the plasma membrane of a beetroot plant is the anthocyanin. It is the anthocyanin that gives the beetroot its characteristics the blue/purple colour. If the cell is damaged in a beetroot plant and the membrane is broken, the anthocyanin leaks from the cell like a dye. This information can be used to observe the rate of diffusion in the investigation. Beetroot pigment is unstable at high temperatures and this causes the cell membranes to break and release the anthocyanin.
Preliminary Studies:
The diffusion of copper sulphate in water. When water is added the copper sulphate starts to dissolve. A particle of blue copper diffuses into the water. At first the copper sulphate is more concentrated at the bottom of the jar, but gradually the particles spread throughout the water, until the concentration is the same everywhere. Diffusion involves the movement of particles from a region of high concentration i.e. the blue copper sulphate at the bottom of test tube towards a region of lower concentration. Similar this type of diffusion occurs in everyday life. Diffusion makes the colour and flavour of tea spread through the hot water.
Apparatus:
Beetroot
Measuring cylinder
Test tubes
Distilled water
Cork borer
Knife
Method:
Before the experiment can start, the beetroot must first be prepared. Using a white tile and a cork borer does this. The same section of the beetroot must be taken in order to keep the surface area the same. To collect a sample of beetroot, push the borer into the vegetable and then withdraw it. The cylinder will remain inside the cork borer, so it must be pushed out. The section of beetroot must then be cut into pieces of 2cm length. During the preparation of the beetroot it is important to remember that in the cutting of the samples some of the membrane is broken. This means some anthocyanin will leak out. This must be completely wiped off the white tile. This means the cut piece must be placed on a new tile before the experiment will start.
During the preparation of the beetroot three water baths must be set up at 25o, 45o and again at 65o . Before the experiment begins the water baths temperatures must be checked using a thermometer and it’s reading recorded.
Using a measuring cylinder measure 50cm2 of distilled water. Next take one test tube and pour the contents of the measured distilled water into the test tube. Place test tube with distilled water into colourimeter and note it’s reading. Repeat this three times as to get an average reading. Place test tube in the test tube rack holder. Using forceps place the sliced beetroot of 2cm into test tube. Start stop clock. After 10 minutes take a pipette and take a 3mm sample of the mixture. Place this sample in a 3mm water cuvette. Place cuvette in the colourimeter and take a reading. Be sure to note the reading in the table. Colourimeter readings should be taken again 20 minutes after experiment and 40 minutes into the experiment these readings should also be noted down. These readings are the control readings for the investigation.
Again using a measuring cylinder measure 50cm2 of distilled water. Next take a test tube and pour the contents of the measured distilled water into the test tube. Using forceps place test tube into water bath 25o. Repeat this part of the experiment three times in order to get an average reading. Do the same for the other two temperatures (45o and 65o) again this has to be done three times to get an average. When the test tubes have reached the right temperature (this can be checked using a thermometer), using forceps place the sliced prepared beetroot into the test tubes and start stop clock. After 10 minutes take a colourimeter reading of the test tube as done in the control section and note down the score Colourimeter readings should be taken again after 20minutes after the experiment has started and at 40 minutes. These readings need to be carried out for every temperature of the three water baths and for all three test tubes in the water bath.
Diagram of experimental set up:
Recording sheet: this is the proposed way of recording the results for the investigation.
My prediction for the experiment is that has the temperature of the water solute is increased the rate at which the cell membrane is broken and the release of the colour pigment will also increases.
The independent variable in the investigation, the variable that is being measured is the temperature of the water. The temperature of the water is constantly being manipulated within the experiment. All other factors of the experiment must be kept the same to avoid any other extraneous variables affecting the results. The dependent variable in the experiment is the rate at which diffusion of the beetroot pigment occurs within the water. The dependent variable can only occur when the independent variable has occurred.
The control part of the experiment is the diffusion occurring at room temperature. This states the rate of diffusion occurring without any manipulative factors taken place.
The safety issues, which may arise from the experiment, may occur in the preparation of the beetroot samples particularly in the cutting. Following the handling of sharp objects procedure can minimize this. Other safety issues may occur when extracting solution samples from the test tubes in the water baths. Wooden tongs can be used take the test tubes out of the water bath thus avoiding any risks of burns.