Friday, 22 May 2015

Time period of spring motion

Equipment

Spring
Masses
2 x Clamp & stand
Datalogger & light gate
Paper
Sticky tape

Method

Set up one clamp and stand to hold the spring with masses on.
Set up the second to hold the light gate of the datalogger.

Add a small (1cm width) paper flag to the masses using the tape to secure it, the flag should be positioned so it passes completely through the datalogger light gate.

Set the datalogger recording and pull the masses down and release. Use the datalogger output to find the time for 10 oscillations.

Add another mass onto the hanger and repeat - you will need to adjust the position of the light gate so it is in line with the rest position of the flag.

Risks

The spring and masses may become unstable, ensure the equipment is kept central on the bench and that the spring is firmly attached to the clamp. The masses should only be pulled down a couple centimetres to avoid the system becoming unstable as the masses will start to swing as well as bob.





Physical factors affecting lung volume


Olympic cyclists tend to have larger than average lungs for their size. This experiment looks for links between physical attributes and lung volume which would enable people to predict their likelihood of success should they take up the sport.


Equipment

Spirometer or other breathing volume measuring equipment (e.g. lung volume bag)
Tape measure
Range of subjects

Method

Measure a range of physical features for each subject such as height, chest circumference, length from between collar bone to sternum, length of forearm etc.

Use the spirometer to record the maximum breath volume of each subject and also their peak flow rate if your device will allow that.

Plot a scatter graph of the lung volume against each physical measurement to determine if there is a correlation between any of the data collected.

Risks

Asthmatics may cough when performing these tests so should either be removed from the sample or ensure they have their inhaler with them. The mouthpiece of the spirometer should be changed or sterilised between subjects.

Thursday, 21 May 2015

Breath volume before and after exercise

Equipment

Breathing bag (long plastic bag with markings to show litres)
Two way mouthpiece
Nose clip
Treadmill (optional)

Method

Place nose clip on the subject and get them to make 5 normal breaths through the mouthpiece and into the bag. The mouthpiece should be of a design with a valve which allows air to enter the mouth on inhalation, with exhaled air being passed into the bag.

Roll the bag down from the mouthpiece end and read off the volume of gas contained within.

Get your subject to perform a light exercise, such as jogging on a treadmill or performing star jumps, for two minutes, with the noseclip removed so that they can breath normally.

Repeat the measurement of air volume produced from 5 breaths.

Another set of exercise should be performed for for minutes and measurements made. This should be repeated with exercise intervals increasing by two minutes each time up to a maximum of ten minutes.

The subject should be encouraged to breath as normally as possible in all cases.

Safety

Should your subject become light headed stop the experiment, remove the mouthpiece and nose clip and allow them to breath deeply for a few minutes. Ensure that the area where the exercise is taking place is free from obstruction. Ensure that your subject is in general good health before taking part. Ensure that the mouthpiece is sterilised prior to use, or has a disposable extension which is used.

Wednesday, 20 May 2015

Fatigue and exercise intensity using hand clenching


Does the intensity of muscle contractions affect the length of time it takes to become fatigued?

EQUIPMENT

Stopwatch
Metronome

METHOD

1. Sit with your stronger arm resting on the table, palm uppermost.
2. Clench and unclench your fist, at a rate of once every 3 seconds in time with the metronome. Record how long it takes to feel so fatigued that it becomes too painful to continue.
3. Rest for 2 minutes, then repeat twice more at the same intensity.
4. Repeat the clenching and unclenching at a rate of once every 2 seconds, then every 1 second, then 2 per second, then 3 per second.
5. You should have 3 repeats at each of 5 different intensities.

Risks assessment

1. Ensure that the proper rest time between repeats is observed, to prevent strain on the arm muscles and tendons.
2. If the rest time is insufficient to fully recover, then extend it to 3 minutes.

Titration to determine volume of acid needed to neutralise an alkali

Equipment

Burette with clamp and stand
Pipette (10ml) with filler bulb
Conical Flask
Funnel
Known concentration (1 molar) Hydrochloric Acid
Unknown concentration alkali solution
Phenolphthalein Indicator
Deionised water

Method

Use the pipette to measure 10ml of alkali solution into the conical flask. Add 5 drops of the indicator to turn the solution pink.

Fill the burette with acid using the funnel, ensuring the tap is closed before starting to fill. Allow some acid to run through to ensure there are no air bubbles in the nozzle. Ensure the the burette is starting at the 0ml mark.

Add the acid to the conical flask 5ml at a time, swirling between each addition to find the rough end point of the reaction (when the solution in the flask goes clear).

Refill the burette, rinse out the conical flask with deionised water and put another 10ml of alkali in there.

Add acid from the burette until you are approximately 5ml from the endpoint, then continue to add acid, but at a much slower rate. Ideally you will add one final drop which will neutralise the solution.

Once you have recorded the volume of acid required repeat twice more.

Risks

Glassware can break if not handled correctly so care should be taken and if anything does break a dustpan and brush should be used to sweep up all the pieces. Acid and alkali can be irritant or worse so goggles should always be worn, care should especially be taken when filling the burette.

Monday, 18 May 2015

Effect of acid type on seed germination

Equipment

4 x petri dishes
cress seeds
absorbent paper such as kitchen towel or blotting paper
1 molar Hydrochloric, Sulphuric and Nitric acids
Water

Method

Place a few layers of the absorbent paper into the petri dishes and soak each one in a different acid, with the final one containing just water.

Sprinkle 25 cress seeds onto the paper and leave for a week in a sunny location. Check the paper each day to ensure it does not dry out.

After one week count the number of seeds that have germinated in each dish and measure the height of the 10 tallest seedlings.

Risks

Goggles should always be worn when working with acids. Any spills should be cleared up straight away.


Thursday, 14 May 2015

Effect of acid rain on plant growth

Equipment

Cress seeds
Absorbent paper
4 Saucers
1M hydrochloric acid
Water

Method

Place some of the absorbent paper on each of the saucers.
One should be soaked in the acid, one from a 50/50 solution of acid and water, one from a 10% solution of acid and water and one with just water.
Place 20 cress seeds on each saucer.
Leave for one week for the seeds to grow ensuring that the paper does not dry out.
Ensure the saucers are as close together as possible to avoid variance in temperature and light received.

Measure the height of each of the plants that has germinated, and also record how many of the plants germinated.

You may also record any other pertinent information about the plants such as leaf colour or shape.

Safety

Ensure goggles are used when working with acidic solutions, also ensure that the saucers are left to germinate in an area where they will not be knocked onto the floor and break.

Friday, 8 May 2015

Refraction angle vs incident angle

Equipment

Rectangular glass block
Raybox with single slit
Power supply
Protractor
Ruler
Pencil

Method

Draw round the glass lock and shine the ray from the raybox so that it enters one long side of the block and exits the other.
Mark the centre line of the two rays using the pencil.
Remove the block and join the dots to the outline of the block. Connect up the entry and exit points within the block outline.
Mark on a normal where the ray enters the block outline.
Measure the angles of incidence (outside block) and the refracted angle (inside block)
Record the pair of angles.
Repeat for a number of different angles of incidence.

Safety.

Rayboxes can get hot whilst in use, leave to cool down before putting away, take care when moving the box between tests, switch off between measurements.

Thursday, 7 May 2015

Measuring the refractive index of a rectangular prism

Equipment

Rectangular prism (glass or perspex)
Raybox with single slit fitted and power supply
Plain paper
Ruler
Sharp pencil
Protractor

Method

Place the block on the paper and draw around it.
Mark on a normal line perpendicular to the block outline midway along the long side of the block so that it extends to within the block outline drawn.
Use the protractor to measure and mark out lines every 10 degrees from the normal, up to 60 degrees.

Shine the ray from the raybox so that it enters the block at an angle of 10 degrees from the normal.
Carefully mark 2 or three dots in the centre of the ray leaving the block on the opposite side.
Remove the block and use a ruler to join these dots to show the path of the exiting ray up to the block outline.
Use the ruler join up this point with where the normal intersects the other side.

Measure the angle between the refracted ray drawn inside the block and the normal and record this.
Repeat this drawing on of dots and measuring the angle of refraction for each angle of incidence.

Calculate the refractive index for each pair of readings by finding sin i / sin r - then calculate a mean value from the five values of refractive index calculated.

Safety

Rayboxes can and do get hot whilst in use so care should be taken to allow it to cool before packing away. Glass or perspex prisms could shatter if dropped onto a hard surface - if so any broken material should be cleaned away using a dustpan and brush, not fingers.

LDR response to variations in light intensity

Equipment

LDR
Ammeter
Voltmeter
6V power supply
Connecting leads
Desk lamp
Ruler

Method.

Connect the LDR and ammeter in series with the power supply. Connect the voltmeter in parallel to the LDR.
Set the LDR up so it is 10cm from the bulb.
Switch on the lamp and record the ammeter and voltmeter readings. Switch off the lamp, then back on and repeat the readings. Repeat once more.
Move the LDR 5cm further from the bulb and take another 3 sets of readings.
Continue until you reach 40cm from the bulb.

Take the voltage reading and divide by the current to find the resistance of the LDR in each case.

Safety

The bulb being used may get hot. Care should be taken to let it cool before packing away.

Wednesday, 6 May 2015

LDR vs light colour


Equipment

Red, green, blue, IR and UV LEDs
LDR
4.5V power supply
Crocodile clip leads
Digital multimeter
Black cardboard tube

Method

Connect an LED to the power supply and insert into one end of the tube so that it is the only light source.
Attach the LDR to the multimeter set to read Ohms and place in the other end of the tube.
Switch on the power supply and record the reading shown on the multimeter.
Repeat for each of the LED colours.

Ensure that the distance between the LED and LDR does not change and that the LED is the only light source able to affect the reading on the LDR.



Tuesday, 5 May 2015

Catalyst mass and volume of gas produced in decomposition of Hydrogen Peroxide


Equipment

Powdered catalyst
Hydrogen peroxide
250ml measuring cylinder
Washing up liquid
Top pan balance

Method

Add 50ml of Hydrogen Peroxide to the measuring cylinder and 5ml of washing up liquid.
Drop in 0.1g of the catalyst and measure the maximum height of the bubbles produced.
Repeat for different masses of catalyst.

Risks

Goggles should be worn at all times. Using too much catalyst may result in the foam overflowing the measuring cylinder so a supply of paper towels should be kept ready to clear up any spills.

Catalyst effect on Hydrogen Peroxide

Hydrogen peroxide naturally decomposes to release oxygen. The presence of a catalyst will increase the rate of decomposition. This experiment looks at how different catalysts affect the decomposition rate.

Equipment

Conical Flask
Bung & delivery tube
Gas syringe
Stopclock
Measuring cylinder
Top pan balance
Hydrogen peroxide
A selection of catalysts e.g manganese oxide, lead oxide, liver

Method

Measure out 100ml of hydrogen peroxide into the measuring cylinder  and pour into the conical flask.
The bung and delivery tube should be connected to the gas syringe.
Add 0.5g of the chosen catalyst to the conical flask, insert the bung and start the stopcock.
Time how long it takes for 20ml of gas to be produced.
Repeat three times for each catalyst.

Risks

Wear goggles when measuring out liquids. Wipe up any spills straight away. Ensure you work in the centre of the bench and that all glass ware is kept away from the edge. Use a dustpan and brush to clean up any breakages if they occur.