A-Level Physics Practical Handbook (9630) PDF

INTERNATIONAL AS AND A-LEVEL PHYSICS (9630) PRACTICAL HANDBOOK BOYLE’S LAW STUDENT SHEET METHOD Remove the plunger from the syringe and measure the diameter of the rubber seal, d, using the micrometer. C...

INTERNATIONAL AS AND A-LEVEL PHYSICS (9630) PRACTICAL HANDBOOK BOYLE’S LAW STUDENT SHEET METHOD Remove the plunger from the syringe and measure the diameter of the rubber seal, d, using the micrometer. Convert this into metres. Calculate the cross-sectional area of the seal A d 2/4 in m2. Replace the plunger and draw in 4.0 ml of air. Fit the rubber tubing over the nozzle, fold the tubing over and clamp it with the pinch clip as close to the nozzle as possible. Set up the apparatus as shown in the diagram initially with the 100 g mass holder carrying one 100 g mass. Ensure that the string is securely attached to the plunger handle. The clamp should be above the plunger so that the scale can be read. Clamping the syringe barrel can distort it, making it more difficult for the plunger to move freely. Consequently ensure the clamp is high enough on the barrel above the position where the plunger moves. There Copyright © 2018 Oxford International AQA Examinations and its licensors. All rights reserved. 83  INTERNATIONAL AS AND A-LEVEL PHYSICS (9630) PRACTICAL HANDBOOK should be sufficient room below the masses so that the plunger can move down as masses are added. Gently move the plunger up and down a few millimetres to ensure it is not sticking. Read the new volume on the syringe scale (fractions of a division should be estimated). Repeat the procedure with an extra two 100 g masses added to the holder each time, up to a total mass of 1000 g. The whole experiment should then be repeated to obtain a second set of results, and the mean volumes found. The force exerted by the masses can be calculated using F = mg where m is the mass in kg and g , the gravitational field strength, is 9.81 Nkg–1. The pressure exerted by this force on the air sample is then F/A in Pascals (Pa). Convert this into kPa. This should be subtracted from standard atmospheric pressure, 101 kPa, to obtain the pressure of the air sample, P. (Note: the initial volume of the air with no masses hung on the loop will be at standard atmospheric pressure). A graph of 1/V against P should then be plotted (where V is the mean volume of the air sample for each value of P). Provided care has been taken to ensure the plunger does not stick, a reasonable straight line through the origin should be obtained. (Any slight sticking could result in a graph which curves slightly and/or does not pass through the origin). Copyright © 2018 Oxford International AQA Examinations and its licensors. All rights reserved. 84  INTERNATIONAL AS AND A-LEVEL PHYSICS (9630) PRACTICAL HANDBOOK CHARLES’S LAW STUDENT SHEET METHOD Set up the apparatus as shown in the diagram with the open end of the capillary tube at the top. Allow the boiled water from the kettle to cool a little before pouring it into the beaker. The hot water should cover the air sample. Stir the water well using the thermometer, read the value of its temperature, , and the length of the air sample, l, on the 30 cm ruler (see diagram above). Allow the water to cool by 5 °C and repeat the procedure until room temperature has been reached. (The cooling process can be speeded up by pouring a little water out of the beaker and topping it up with cold water.) Plot a graph of l against. Start the axes at a convenient value, and use a scale which will give a spread of points over at least half the graph paper in both directions. Draw the best straight line of fit though the points and find the gradient, m. The form of the graph is l = + c, where c is the value of l when = 0 °C. The value of c can be found by reading a pair of values for length and temperature for a point on the straight line (l1 and 1, say). Then c = l1 - 1. An estimate of the value of absolute zero, 0, can then be found by substituting l = 0 into the equation for the form of the graph: 0 = 0 + c so 0 = -c/m. Copyright © 2018 Oxford International AQA Examinations and its licensors. All rights reserved. 85