Monday, 18 April 2016

Friction on a block vs tilt angle

Equipment

Wooden block
Balance
100g masses
Tape
Wooden board (e.g heatproof mat)
Ruler, clamp and stand
Pen

Method

Weigh the wooden block then position on the board and mark its position with the pen to ensure it starts in the same place each time.

Set the ruler up so it is held vertically in the clamp and stand, and line up with the rear side of the board.

Tilt the board slowly by raising the edge next to the ruler and watch for when the block starts to move. Record the height the board has been raised to, then reset and repeat the measurement twice more.

Tape a mass to the top of the block ensuring the tape does not go onto the contact surface at the bottom of the block.

Repeat the experiment, and continue adding masses and taking readings until you have 500g added to the block.

Do not use a different block or board, as the materials in contact and the surface area of contact may affect the outcome of the experiment.

Safety

Ensure the work is carried out in the middle of the table so the masses do not fall onto the floor or feet. Make sure the masses are well secured.

Saturday, 16 April 2016

Temperature and rate of reaction

Equipment

Water bath
Sodium Thiosulphate solution
Hydrochloric Acid
Measuring cylinders
Boiling tube
Test tube
Led torch
Light sensor & datalogger
Thermometer
Clamps and stands
Goggles

Method

Add 10ml of the Sodium Thiosulphate solution to the boiling tube and place in the water bath set to 25 degrees C.
Add 5ml of the acid to a test tube and also place this in the water bath.
Set up a clamp and stand to hold the boiling tube with the LED torch on one side of it and the light sensor on the other. Set the datalogger to measure light intensity vs time.
When both liquids are at the correct temperature take them out of the water bath, fix the boiling tube into the clamp stand between the torch and the sensor, so that the sensor is against the tube and the light shines through the liquid then tip in the acid.
When the light intensity measured stops changing stop the datalogger.
Repeat the experiment using temperatures of 30, 35, 40, 45 and 50 degrees C.

Risk assessment

Be careful when clamping the boiling tube so that it does not get crushed. Clear up spills straight away. Goggles should be work when pouring liquids.


Rate of reaction, concentration & temperature

Equipment

2cm strips of Mg ribbon
Different concentrations of Hydrochloric acid (0.1, 0.5, 1 and 2 molar)
Test tubes
Test tube rack
Measuring cylinder
Thermometer
Stopclock
Goggles

Method

Place 10ml of the first concentration of acid to be used into a test tube. Place in the thermometer and record the temperature of the acid.
Drop in one of the Mg ribbon strips and start the stopclock.
Observe the reaction, looking for gas being produced. When the reaction stops stop the stopclock. If there is any of the Mg ribbon left this should be noted in an observations column. Note the end temperature.
Repeat this twice more using the same concentration of acid. Repeat the whole process of three tests with each different concentration of acid.

Safety

Goggles should be worn throughout the experiment. Spills should be mopped up straight away. Extra care should be taken when handling the most concentrated acid.

Analysis

The rate of reaction is affected by both concentration and temperature. Does the heating effect of the reaction affect it's rate? How could the above exepriment be adapted to eliminate the heating effect of the reaction and that there may not be enough reactants to complete the reaction?


Thursday, 14 April 2016

Photosynthesis rate vs light colour in pond weed

Equipment

LED full spectrum lamp
Couloures gel filters (red, green, blue)
Boiling tube
Clamp & stand
Ruler
Stopclock
Water
Sodium bicarbonate (Baking Soda)
Cabomba pond weed (Elodea may also be used)

Method

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

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

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

Repeat the entire experiment having removed the first colour filter and adding the next.

Ensure that the distance from the lamp to the boiling tube does not change so that the light intensity on the pond weed is constant - this will ensure the results are valid and make the experiment a fair test.

Monday, 7 March 2016

Factors affecting cooling of water

A number of factors can affect the rate of cooling of an object.

These are :

Surface area to volume ratio; number of layers of insulation; type of insulation; colour of object; starting temperature of object.

Any investigation into one of these factors will need to carefully control the others to make sure they do not have an effect on the outcome.

The simplest way to identify how each of these factors affects the cooling is by examining the cooling curve for hot water.

A known volume of hot water should be placed in a container. The experiment should then be set up so that the temperature of the water can be measured at 30 second intervals over 10 minutes.

By plotting these results a cooling curve for those conditions can be obtained.

the experiment can then be repeated, changing one of the variables - for example adding a layer of insulation, or using a different shape container.

By comparing the cooling curves for the different conditions we can see both the overall effect after 10 minutes, and determine how the rate of cooling is affected in each case.

Friday, 5 February 2016

Temperature difference and cooling of water

Equipment

4 cups of the same size (e.g drinks cups)
lids with small holes in centre
datalogger and 4 temperature probes or 4 thermometers
Kettle
100ml measuring cylinder
stopclock


Method

Heat water in the kettle until near boiling.

Very carefully measure 100ml hot water and put into cup 1.
Use 80ml hot water and 20ml cold for cup 2, 60 / 40 for cup 3 and 40ml hot, 60ml cold for the final cup.

Add the lids and put the temperature probes through the holes. Thermometers could be used if you have no datalogger - in this case note the start temperature of each cup. Start the stopclock.

After 10 minutes pass stop the datalogger or record the temperature from the thermometers again.

Risks.

Spilled water can cause falls if not cleared up swiftly. Hot water can cause scalds, great care should be taken when using hot water, and insulating gloves may need to be used if something is too hot to comfortably hold.

Temperature and viscosity of oils

Equipment

Water bath
Vegetable oil
Boiling tube
Measuring cylinder
Beaker
Polystyrene cup with hole in bottom
Clamp stand
Bung to fit hole mounted on a rod
Stopclock

Method

Heat 50ml of the oil to 50 degrees C in a boiling tube in the waterbath.
When warmed add to the polystyrene cup (with the bung in) held in the clamp and stand.
Remove the bung and start the stopclock.
Stop the stopclock when the oil has run through into the beaker.

Repeat twice more at this temperature, reheating the oil each time and ensuring you start with 50ml each time.

Repeat at 10 degree temperature intervals down to 20 degrees C.

You may wish to use an alternative method of letting the warm oil run from an object if there is other equipment you can use.

Risks

Do not heat above 50 degrees C to prevent the risk of burns. Ensure any spilled oil is cleared up as soon as possible to avoid slips and falls.