Pressure Essays - State Functions, Thermodynamic Properties

Pressure Aim: To find out the effect of temperature on the pressure of air. Apparatus: 400ml beaker Bunsen burner Data Logger Pressure sensor Temperature probe Round bottom flask Connecting leads Tripod Gauze Plastic tubing Clamp stand Heatproof mat Water Diagram: Method: 1. Set up the apparatus as shown in the diagram. 1. Next, take the readings of the pressure and temperature at intervals of 5C, ending the experiment at 90C. 3. Repeat the experiment three times for a good average. 4. Record all results in the data logger and transfer them to a computer. Safety: Wear goggles Tie hair back Tie all loose clothing Handle all glass with care Avoid putting wires near the flames Do not spill water; this will make the surface slippery Fair Test: Use the same equipment for each trial Have the same time interval in each trial Make sure the same amount of water is used in each trial Make sure the flask is put into the beaker at the same depth Use the same size beaker in each trial Try to keep the flame the same in each trial Prediction: Particles of air are constantly moving around at different speeds. If the air is trapped inside a container, (e.g. a flask like the one used in this experiment) then the particles will hit the inside walls of the container with enough force to create pressure. Sometimes the particles move around fast. This means they have more kinetic energy. They may have more kinetic energy, because the air may be being heated or perhaps the air is more concentrated. However, if the air particles have more kinetic energy, they will hit the container walls with a larger, stronger force. This then creates more pressure, which is detected by the pressure sensor. (Physics, Tom Duncan, Pages 158-159) When the air contained in the flask, is heated, the temperature rises and the molecules gain more kinetic energy. This means the particles move around faster, causing the average pressure to increase. (GCSE Physics, Foulds, Page 158) In this experiment, we kept the volume of air constant, while the temperature is changed. The three pressure laws, one of which states that the pressure of a gas is directly proportional to its temperature. Can be written as P T Where P is Pressure in KPascals and T is Temperature in Kelvins. This must mean that if the temperature is doubled, the pressure will also double. If the temperature is halved, the pressure will also be halved. The reason why this happens is because at a higher temperature the gas particles have more kinetic energy and hit the container walls harder which results in more pressure. Example: If the temperature is 25C (298K) and the pressure is 1.0 KPa, then doubling the temperature to 50C (323K) should double the pressure to 2.0 KPa. If the temperature is 25C (298K) and the pressure is 1.0 KPa, then trebling the temperature to 75C (348K) should treble the pressure to 3.0 KPa. If this knowledge is put into a graph, where the average pressure in KPascals is plotted against the Temperature in Kelvins, I should get a graph which looks like this: - The graph shows the directly proportional relationship between pressure (KPa) and temperature (Kelvins). With my results from the experiment, I will draw and plot an accurate graph like the one above. Results: Tempe-rature (C) Pressure (KPa) Average Temperatur-e in Kelvins Average pressure in KPa (2d.p) Trial One Trial Two Trial Three 25 0.4 0.7 2.0 298 0.4+0.7+2.0 3 30 1.9 2.2 5.4 303 3.2 35 4.1 4.0 8.1 308 5.4 40 5.8 5.7 11.2 313 7.6 45 7.4 7.2 15.0 318 9.9 50 9.6 8.8 18.7 323 12.4 55 10.5 10.3 22.7 328 14.5 60 12.4 11.8 27.3 333 17.2 65 13.7 13.2 31.2 338 19.4 70 15.1 14.5 33.6 343 21.1 75 16.6 15.8 35.7 348 22.7 80 17.9 17.0 38.7 353 24.5 85 19.3 17.8 43.6 358 26.9 90 20.5 18.6 46.1 363 28.4 Analysis (continued): From my results and graph, I have found out that as the temperature increases, the pressure also increases. (School Notes, Plashet School) To prove this using my graph, I will quote five values for temperature and pressure, from my graph. Temperature (Kelvins) Pressure (KPascals) 303 3.2 328 14.5 348 22.7 363 28.4 This table clearly shows that as the temperature increases, the pressure increases too. Increasing the temperature by ten Kelvins, i.e. from 303K to 313K, the new pressure is increased by a factor