Wednesday, 10 October 2012

Viscosity of oils

Information

This method uses an instrument known as a cup viscometer to measure the viscosity of a fluid.  A cup viscometer is essentially just a smooth sided cup with a hole in the bottom. A preliminary experiment may be required if you are making a cup viscometer to determine the correct volume of oil and hole size to use. You need to be able to use the same cup for all your oil samples and it should be set up such that the oil does not drain so quickly it is difficult to time, nor that it takes so long as to be impractical to complete multiple tests in a reasonable period of time.

Equipment

Clamp and stand
Cup viscometer
Bung for hole in viscometer
Collecting beaker
Measuring cylinder
Stopclock
Samples of different oils

Method

Set up the viscometer in the clamp and stand so that the beaker can be placed below it and you can see the oil flow.
Place a known volume of oil into the viscometer with the bung in the hole.
Place the collecting beaker under the hole.
Start a stopclock as you remove the bung and wait for the oil to drain.
When the oil has finished draining stop the clock and record the time.
Repeat twice more for this oil sample and repeat the whole process for each oil sample to be tested.

Sometimes very viscous oils will start to drip during the final parts of draining. If this is the case it is suggested that you time until each oil first starts to drip.

Try to ensure that the room temperature and thus oil temperature remains constant as the temperature of the oil affects the flow rate.

Energy stored in food 2

Equipment

Bunsen burner
Clamp & stand
Metal tin
Cork & pin
Measuring cylinder (25ml)
Datalogger and temperature probe
Top pan balance
Food samples

Method

Set the metal tin up above the cork and pin using the clamp and stand to hold it in place.

Add 20 ml of water to the tin and place the temperature probe, connected to the datalogger, into the tin.

Measure out 5g of the food sample and attach to the pin. Start the datalogger, get the food sample burning and ensure it is placed directly under the tin. Use the datalogger to record the maximum temperature of water reached.

Empty the tin and repeat twice more with fresh water for the first food sample. Repeat the whole process for each food sample you have.

Use the data from the datalogger to analyse how much energy is contained in each food sample. The larger the temperature rise the greater the energy contained within the food. You may also look at the graph the datalogger produces to determine the rate at which this temperature rise occurred.

Choice Chambers 1 - Light & dark

Equipment

Choice chamber
Paper to black out half of the choice chamber
Woodlice (At least 10)
Container to store woodlice with bark/leaf mould

Method

Set up the choice chamber so that half of it is dark and half of it is open to the light. Taping paper to the lid, base and around the sides may be a good way to do this.

Introduce a known number of woodlice, at least ten, to the center of the choice chamber and replace the lid, ensuring the covered halves line up.

Start a stopclock and on the minute for ten minutes count the number of woodlice in the exposed half. Note down any behaviour you notice too, for example how far into the light half do the woodlice tend to go.

Repeat the experiment three times, if possible with different woodlice.

Ensure at all times that you are extremely careful with handling the woodlice and that they have as natural an environment as possible when not within the choice chamber. Also ensure you thoroughly wash your hands after the experiment has been concluded and you no longer need to handle the woodlice.

Monday, 8 October 2012

Energy stored in food

Equipment

Boiling tube
Thermometer
Clamp & stand
Cork and pin
Measuring cylinder (25ml)
Bunsen
Goggles
Top pan balance
Flammable food samples

Method

Set up the clamp and stand to hold the boiling tube a known distance above the cork and pin to ensure the same level of heat flow into the boiling tube with each test.
Measure out 20ml of water and place it in the boiling tube and clamp into place.
Add the thermometer to the tube and note the water temperature.
Find the mass of the food sample you are using, note this down and then place it on the pin.
Light the food sample and then quickly position it under the boiling tube.
Once the food sample has finished burning record the temperature of the water.
Repeat three times for each food sample with fresh water.

Safety

Be careful of all hot materials, such as the pin and boiling tube. If the water temperature has raised significantly collect a fresh boiling tube rather than putting cold water in to a hot tube as it could shatter.

Analysis

Work out the temperature rise and multiply this by 84J per degree to get the energy transferred. Divide this answer by the mass of food sample used to find the energy per gram of food.

Hard water testing method

Equipment list

Measuring cylinder (10ml, 50ml)
Boiling tubes
Bungs to fit boiling tube
Rack
Stopclock
Ruler
Soap solution
Selection of waters to test.

Method

Measure out 25ml of water to be tested and pour into the boiling tube.
Measure out 2ml of soap solution and add to the boiling tube.
Insert the bung and put your thumb over the top.
Use the stopclock to time vigorously shaking the tube for 15 seconds.
Place the tube into the rack and note the height of the foam formed from the water surface to the top of the lather.
Repeat three times for each water sample to find a mean.

Safety

Ensure the bung does not slip out during the shaking. This could go into the eyes or could leave a slip hazard. Should any tubes be droped and broken any spills should be cleared up straight away.

Results

The hardest water should produce the least bubbles and also produce a soap scum (Calcium Stearate)


Water hardness - bulk test


What is hard water?

 The hardness of water has a direct effect on the ability to form a lather when mixed with soap. This means that you will end up using more soap to achieve the same froth and get the same cleaning effect as in a soft water area. It also leaves a soap scum which does no occur as much in softer water areas. Typically soft water is found in areas such as Cornwall where the underlying rock is granite. In areas such as Hampshire the the water passes through chalk deposits on its way to aquifers, and this is where the additional calcium ions that make the water hard are picked up.

Testing for water hardness.

As indicated above, testing for water hardness is relatively simple. All you need is a sealable and see through container such as an empty drinks bottle. Half fill it with water and add a few drops of washing up liquid, close the lid and shake vigorously. The less foam produced and the more milky looking scum on the surface the harder the water you have.

Some forms of hard water can be 'cured' by boiling the water, but this only works if the Calcium present is in a hydrogen carbonate form. Other sorts of calcium salts mean that the water is permanently hard and will not be softened by boiling.

Pendulum length and period

Equipment

Clamp & stand
Cotton or string
Plasticine
Stopclock

Method

Depending on the height of your stand set the range of lengths of string you will test - 5 to 50 cm is a suggested value.

Clamp the string at the desired length and raise the pendulum, keeping the string taut.

Release the pendulum and start the stopclock. Time how long it takes for 10 swings to complete, remembering that one swing is a complete motion from left to right and back to the left again. Timing 10 swings (or more if you wish) will help reduce the error per swing.

An alternate method to improve the timing would be to set the pendulum up with a light gate and datalogger, so that the pendulum bob breaks the beam of the light gate. This would only time one swing.

Take three or more sets of results for each length to enable errors to be spotted and eliminated when you calculate the mean value for one swing at each length.

This experiment is generally safe, with the only real hazard being knocking over the clamp stand. This can be avoided by placing it in the middle of the bench, or alternatively using a g-clamp to secure it. It is advised that large mass bobs are not used as this will also affect the stability of the experiment.

Finally plot your results on a graph. If you have time you may wish to play a second graph of bob length against period squared - this second graph will end up as a directly proportional line if you have made your measurements carefully enough.

Damping of pendulum motion

Introduction

This experiment aims to find the relationship between surface area of a pendulum bob and the time taken for the pendulum to come to rest.

Equipment

Clamp & stand
Fine wire or fishing line
Pendulum bobs of differing cross sectional area (spherical or cylindrical bobs will work best)
Stopclock
Ruler

Method

The pendulum should be set up with a known length of wire, e.g. 50cm between pivot and the centre of mass of the bob.

The bob should be raised to one side such that it is elevated 10cm from its rest position and the line is taut.

As the bob is released the stopclock should be started and the pendulum should be observed until it comes to rest, at which point the stopclock should be stopped and time recorded.
The experiment should be repeated three times with each bob.

Care should be taken to ensure that the centre of mass is at the same distance from the pivot so that the effective length of the pendulum remains constant.

Analysis

The cross sectional surface area of the bob should be plotted against the time taken for the bob to come to rest.

Monday, 28 May 2012

Photosynthesis Rate vs Light Intensity in Elodea

Equipment

LED full spectrum lamp
Boiling tube
Clamp & stand
Ruler
Stopclock
Water
Sodium bicarbonate (Baking Soda)
Elodea pond weed

Method

Make up a 0.2% solution of the Sodium Bicarbonate and water to provide a source of Carbon Dioxide for the Elodea.

Fill the boiling tube with the solution and add a piece of Elodea such that there is 2cm of solution present above the Elodea. Clamp this in place making sure the that clamp obscures as little of the Elodea and solution as possible. Gently tap the tube to dislodge any gas introduced to the tube with the Elodea.

Set up the LED lamp at a 5cm distance from the side of the boiling tube. A normal lamp can be used, however the temperature increase caused by using an incandescent lightbulb will introduce an error into your experiment as temperature also affects the photosynthesis rate. For improved results ambient lighting should be kept constant or the experiment should be done using the LED lamp as the only source of light.

Wait for the Elodea to start producing bubbles. Start the stopclock and count the bubbles produced over a one minute period. Repeat measurement a further two times.

Move the lamp further away from the Elodea by between 5cm and 10cm depending on how many measurements you wish to take. Wait two or three minutes for the rate of bubble production to settle and then repeat the measurements of the bubble count over a minute.

Analysis

Light intensity obeys and inverse square law - this means that if you double the distance you quarter the intensity. To analyse your results you should square the distance between the lamp and the Elodea and then take the inverse of this number to plot the x axis of your graph. By plotting this against the number of bubbles produced you will be able to determine the relationship between light intensity and photosynthesis rate.

Rate of photosynthesis & light intensity

This experiment will need careful setting up to give you valid results.

First you will need to source some pond weed, Elodea or Cabomba will work. You will also need a large beaker or ice cream tub and a clear measuring cylinder - a glass one would be best. Finally you will need a lamp, a ruler and a stopclock.

The pond weed should be placed into the measuring cylinder and then this should be filled with water in the ice cream tub and then inverted so that the measuring cylinder is full of water. Set the lamp up at a known distance from the pond weed and start the stop clock.



It is up to you how long you leave the equipment set up like this, however the longer you can leave it the more gas will be produced. You will need to record the volume of gas produced when you return to the experiment.

Replace the water in the measuring cylinder set up, move the lamp to a new distance from the pond weed and then leave the equipment for the same time as before.

Repeat again for at least one more distance between lamp and pond weed, however if you can do more then do.

If you are leaving the equipment set up for a significant length of time unattended you will need to make sure that the measuring cylinder is supported - especially if it is made of glass. You should also ensure that there is nothing resting on or near the lamp as depending on the type of bulb used the lamp could become hot after extended periods of operation.


Hookes Law 2 - elastic bands

Equipment list

Elastic bands
Masses
Ruler
Clamp & stand
Foam
Goggles

Method

Set up the clamp and stand so it holds the ruler and the elastic band.
Place the foam under the elastic band and put on the goggles.
Add masses to the elastic band and measure how much it stretches by as you add each mass.
Should you overextend the elastic band and it breaks the foam will catch the masses and any flying pieces of rubber will not go in your eyes.
Record your results in a table.
If you have time repeat your experiment a couple more times and calculate an average of the extensions.
Plot a graph of your results.

Extension

Try the experiment again with two and three elastic bands.
Try different configurations of the elastic bands, knotting them together lengthways, or placing them side by side.
How does this affect the shape of the graph and why?



Sunday, 13 May 2012

Hookes law 1

Information

This experiment will allow you to find the spring constant of the spring you are using and, if graphed correctly allow you to work out the energy transferred into the spring when it is deformed past the limit of proportionality.

Equipment

Clamp stand
Boss head
Clamp
Extending tape measure
Metal spring
Mass hangers (kilograms in 100g divisions)

Method


Set up the equipment as shown in the diagram below
Measure the length of the spring with no mass attached
Add a 0.1kg mass, measure the extension of the spring
Keep adding masses and measuring the extension until the spring stretches past the limit of proportionality (it will not return to its original length in this case)
Remove the masses one at a time until all the masses are removed.

Analysis

Calculate the force applied (1kg = 9.8N of force)
Plot a graph of the results with the Extension on the x axis. Use separate colours for adding and subtracting masses so you have two lines.
The slope of the linear part of the graph is the spring constant for the spring.
The area between tho two lines represents the energy that has been transferred to the spring.





Exothermic reaction of Calcium Oxide 2

Equipment

calcium oxide powder
water
spatula
thermometer
stirring rod
5 polystyrene cups
stopwatch

Method

Half fill each of the cups with water so that they are all full to the same level
Record the temperature of the water
Add 1 spatula of CaO to the first cup, 2 spatulas into the second one etc and stir to make sure it all dissolves
Wait 1 minute and measure the temperature in all the cups again
Rinse all the cups out and repeat the experiment another two times
Calculate the average temperature rise for each cup

Safety

CaO is an irritant and contact with skin should be avoided.



Exothermic reaction of calcium oxide 1

Aim

To see how the mass of calcium oxide affects the temperature change produced in a reaction with water

Theory

Adding Calcium Oxide to water produces an exothermic reaction as aqueous Calcium Hydroxide is formed. The total energy released will increase as more bonds are broken by using a greater mass of Calcium Hydroxide

Equipment
CaO powder
De-ionised water
50 ml measuring cylinder
Insulating beaker
Balance (.01g resolution)
Temperature probe and data logger
Stirring rod

Method

In an insulating beaker combine 50ml of water with 1g of CaO
Stir and record the maximum temperature reached using a temperature probe and datalogger
Repeat the experiment by using fresh water and increasing the mass of CaO used by 1g

Safety

As CaO will react exothermically with water care should be taken to avoid contact with skin where reaction with moisture could cause irritation and in extreme cases burns.

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

Equipment

Test tube & bung
Test tube rack
Oil
Water
Emulsifier
Measuring cylinder
Pipette
Stopclock

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.

SAFETY!

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