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.