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In this lab we are going to investigate behavior of gas by working with a molecular model. Factors that effect gas behavior our pressure, temperature, volume and the number of moles. We are going to keep to variables constant and record the relationship or change in the remaining factors.
Independent variables: Temperature, number of moles, volume
Dependent variable: Pressure
Controlled variable: apparatus used (computer program downloaded from the internet), volume and number of moles
Question: What is the relationship between pressure and temperature of a gas filled container with constant volume and number of moles?
Hypothesis: temperature and pressure are directly related. As temperature increases pressure increases. Pressure is directly proportional to temperature when the number of moles and volume are kept constant.
Log on to the Internet and visit heinnemann.co.uk/hotlinks and enter the express code 4266S. Click on weblink 3.2 the simulation on the right will appear. In this simulation one can set the parameters as per desire. For this experiment we need to set the volume and number of moles constant. Three trials are done for accuracy. For the first trial, we need to set the volume constant. The volume will remain set to the default value. Then pump 100 heavy species particle in the container and keep them the same until the next trial. The temperature will automatically go to 300K, remove heat to lower the temperature to 150K. Record the pressure produced.
Add 50K each time, before taking another reading until the temperature reach 500K. Record the change in pressure with simultaneous temperature in a table. Before starting the next trail hit the reset button. Before starting the second trail change the depth of the container to 3.4nm. Measure the depth with a ruler (the ruler is given as a tool for measurement).
Pump 100 more heavy species in the container to make a total of 200 particles. Increase the temperature as done before with similar intervals and record the pressure in form of a table. Hit the reset again and start the final trail. For the third trial, increase the depth of the container to 9nm and pump in a total of 300 heavy species particle. Record the temperature and pressure in a table. The uncertainty in this experiment for temperature is +0.5K and for pressure is +0.5 Pa. Use the tables to graph the data to show the relationship between temperature and pressure.
Conclusion and Evaluation:
From the data collected and the graphs processed we can make out that pressure is directly related to temperature when the number of moles of particles and the volume of the container is kept constant. We know that as temperature increases the particles gain more energy and collide at a faster rate with each other and the wall of the container.
As the number of collisions increases, the more the particles exert force on the walls of the container. The force that the particles have on the walls is known as the pressure. All the 3 graphs have a linear relationship and the slopes of their lines are the coefficient of the temperature because temperature is directly related to pressure. As shown by the graphs temperature is directly proportional to pressure. In other words keep the volume and the amount of gas constant and change the temperature (by heating or cooling) and observe the change in pressure (Pressure law: P=const*T).
The lines are not straight and a line of best fit is used. The unevenness of the lines on the graphs shows that there are slight errors involved in the experiment. The errors included are systematic, analytical and random. As the pressure was fluctuating the value noted was randomly chosen. The temperature was sometimes a point higher or lower, which again caused the pressure gauge to give a slight of value. Also the uncertainty in the measurement of volume showed that there were some errors also included while taking the measurement of the container.
Suggestions for improvements:
The lab was precise because of the number of trials done but it could be accurate by reducing the errors made in the experiment. Try to hit the raise the temperature of the container in the simulation accurately if that is not possible try setting the default temperature to the desired value and record the pressure. This would allow the pressure gauge to be more accurate.
When taking measurement of the container for volume with a ruler try to avoid the parallax error, which is created by not looking at the measurement perpendicularly. Take the mode value from all of the values produced by the pressure gauge and wait a minute or two after setting the temperature and before noting the temperature. This helps to get a more accurate reading because the particles get enough time to settle. By recording the pressure value after giving certain breaks in the experiment will help the lines on all the three graph to be less uneven and more accurate.