Thursday, 16 June 2016

Energy released from fuels

Equipment

Spirit burners with different fuels in (e.g. Ethanol, Propanol, Butanol)
Top pan balance (0.01g accuracy)
Boiling tube
Clamp and stand
Thermometer
Stopclock
Measuring cylinder
Goggles

Method

Place 50ml of water into the boiling tube and place into the clamp. Measure the water temperature.
Place spirit burner on the balance and record the initial mass.
Next place the spirit burner under the boiling tube, light it and start the stop clock, ensuring that the tip of the flame is just beneath the boiling tube.
After 2 minutes have passed snuff out the spirit burner and record the temperature of the water.
Place spirit burner on the balance and record the final mass.
Repeat this twice more using a fresh boiling tube and fresh water and then calculate the average temperature rise divided by the average change in mass.
Repeat the whole experiment three times for each fuel.

Risk assessment

Care should be taken with the spirit burner to ensure you do not spill any fuel. Goggles should be worn when heating liquids. When replacing the boiling tube take care as it will be hot - it should be left in a test tube rack to cool slowly so as not to crack the glass.

Lenses and image formation

Equipment

Power supply
12V bulb in holder
connecting leads
15cm f/l lens
Lens holder
Metre stick
Graph paper

Method

1) Make a table with the following headings

Distance between bulb and lens (cm)
Distance between bulb and image (cm)
Size of image (cm)
Nature of image / Observations

2) Plug the bulb into the power supply and set to 6V – it should not be at full brightness
3) Start with the bulb at one end of the metre stick and have the lens 60 cm from the bulb
4) Hold the graph paper next to the lens and move it away until a sharp image of the filament (the very bright part) has formed – this may be past the end of the metre stick – if so use a second one.
5) Record the distance between the lens and the graph paper in cm
6) Record the size of the image of the filament – one small square on the graph paper is 2mm
7) Record which way up the image of the bulb is on the paper and anything else you think important.
8) Reduce the distance between the bulb and lens to 50cm and repeat the image finding and measurement process.
9) Continue until you reach 10cm between bulb and lens.
10) Write a sentence which describes the pattern s shown in the data.

Extension

Calculate the ratio of the distance between lens and image and the size of the image



SAFETY
The bulb will get hot when working, be careful not to touch it, allow it to cool before clearing away.
Keep walkways clear to avoid trip hazards when light levels are low

Moments and lever effect - distance of effort vs size

Equipment

Metre stick
Triangular block for pivot
Masses (100g, 10g)
Tape


Method

Place the ruler on the pivot so that the pivot is under the 30cm mark. Do not alter this.
Place a fixed mass (e.g. 300g) on the end of the short side of the ruler to provide a fixed load (in this case 3N). Do not alter this either. Tape may be needed to fix this in place.

At the other end of the ruler start adding masses until the short end just lifts. Record the mass needed to make it lift and record the force applied - 100g provides 1N of force.

Repeat 10cm in from the end of the ruler, Keep recording mass and moving in towards pivot by 10cm until 20cm from pivot.


Extension.

Try the same experiment but with the pivot 10cm from the load and 20cm from the load.


Safety

Masses may fall, ensure working in the centre of the desk so that any masses which do fall from the ruler will not fall further onto the floor and feet. The practical should be carried out stood up so that if any masses do fall experimenters can quickly move out of the way.


Osmosis, surface and concentration of solution

Large potato,
Ruler,
Sharp knife,
Chopping board
Paper towels
Scales (0.1g resolution)
Beakers x 4
Water.
Salt
Spatula
Stirring rod
Stopclock
Tea strainer

Method

Carefully cut five cubes of  2cm sides from the potato - ensure they have no skin on.
Dry and weigh the cubes.

In each of four beakers add 100ml of water. Add no salt to the first, weigh and add 5g to the next and so on up to 20g in the last. Stir to ensure all salt is dissolved.

Place a potato piece in each beaker, start the stopclock and time for 10 mins.

Pour each beaker out through a tea strainer - dry and weigh the pieces again.

Record the percentage mass increase, or decrease of each potato piece.

Safety

Knife must be used carefully  - keep fingers well away from cutting surface. Glass beakers could break if not handled well, plastic beakers could be used for this experiment without any adverse effects.


Surface area and osmosis

Equipment

Large potato,
Ruler,
Sharp knife,
Chopping board
Paper towels
Scales (0.1g resolution)
Beakers x 4
Water.
Stopclock
Tea strainer


Method

Carefully cut four cubes of  2cm sides from the potato - ensure they have no skin on.
Leave one cube whole,
Cut one in half to make two 2x2x1cm blocks.
Cut one in four to make four 2x1x1cm blocks.
Cut one in eight parts to make eight 1x1x1 blocks.

Dry and weigh each set of potato pieces and record the masses in a table.

In four beakers with 100ml of water in place each set of potato pieces and start the stopclock.
Time for 10 minutes and then pour each beaker out through a tea strainer - dry and weigh the pieces again.

Use your data to work out the surface area exposed in each case and the percentage mass increase of the potato.

Safety

Knife must be used carefully  - keep fingers well away from cutting surface. Glass beakers could break if not handled well, plastic beakers could be used for this experiment without any adverse effects.