Wednesday, 21 March 2012

Volume of emulsion vs separation time 2

Collect a test tube, stopclock, measuring cylinder and the liquids you will be using.

Add equal volumes of oil and water to a the test tube, followed by the emulsifier you are using. measure out the amount of emulsifier by adding it dropwise from a pipette - ten drops is a good starting point. Each experiment should use the same volume of oil and water, but add another ten drops each time.

Once you have everything in the tube put your thumb over the end and give it a shake so everything mixes. Once you stop shaking start the timer and wait until the oil and water have completely separated. Using coloured water can help you see the difference a bit more clearly.

When you finish make sure to clear down your work area and rinse out the test tubes you have used.

Record the time for each experiment and then use this information to plat a graph to show how the volume of emulsifier affects the time taken to separate.

Volume of emulsion vs separation time 1


Test tube & bung
Test tube rack
Measuring cylinder

Measure out equal volumes of oil and water (4 ml of each works well)
Add to test tube - water first.
Add in volume of emulsifier to be tested - do not use more emulsifier than oil/water.
Insert bung, hold in place with thumb and invert the tube 10 times.
Immediately start the stopclock and place the tube in the rack.
When you can see a clear separation of oil and water stop the stopclock and record the time.

Repeat three times for each volume of emulsifier if you have time.

Instead of different volumes of emulsifier you could try the same volume of different types of emulsifier.

Any spills of oil/water could be hazardous, as could broken glassware. Clean up any spills/breakages immediately.

Solar Cell area vs output 2

Collect a solar cell, desk lamp, multimeter, connecting leads and a piece of dark paper big enough to completely cover the solar cell.

This is best performed in a darkened room. If done in ambient light conditions ensure the light levels are constant.

Measure the area of the solar cell.

Connect the solar cell to the multimeter and set up the lamp so the beam covers the surface entirely. Mark positions and try not to move the lamp or cell again.

Cover the solar cell with the paper and record the voltage.

Uncover a measured area of solar cell (choice of value will depend on your solar cell size) - you should aim to have around 1/10th showing.

Record the value on the multimeter, uncover another 1/10th of the area and son on until the entire surface is exposed to the light.

For best results repeat your experiment 3 times.

Solar Cell area vs output 1

Method for measuring impact of surface area on solar cell output.

Set up practical equipment with a multimeter connected to a solar cell. Place a lamp to shine on the solar cell and make sure you have a large enough piece of paper to cover it. The paper should be opaque.

Cover over the solar cell and record the voltage on the multimeter.

Slowly uncover the solar cell and record the voltage at each step.

If you have time repeat each recording to make sure you have not made any errors.


Watch out for desk lamps with metal shades as these can get hot.