EP Experiment 2
The Constant-Volume Gas Law
The pressure of Jolly bulb
filled with an air of constant volume is measured with a set of discrete
temperatures from the steam point of water to the ice point of water. The
relationship between pressure and temperature is evaluated from the data and
absolute zero is estimated.
Pressure of the gas shows
changes when volume held constant and temperature adjusted. Temperature vary
differently form the freezing point of water to the boiling point of water. Direct proportional relationship is expected from
the pressure and the temperature, which means as the temperature increases
pressure should increase too. Method Half fill the beaker with
ice. Carefully lower the bulb apparatus into the beaker and clamp it. Add cold
water inside the beaker until it covers the whole bulb. Stir the water until it
reaches to a constant temperature of 0 °C. Remove the bulb from the
beaker, remove all remaining ice and fill half the beaker with water and put
bulb into beaker. Put some cold water into beaker. Stir the water until it
stabilises and measure the temperature and pressure. Remove about 1/3 rd of the
water and put hot water from the kettle. Measure temperature and pressure,
repeat this process until the temperature reaches around 70-80°C. Afterwards,
remove all the water remaining and replace it with boiling water.Overall 10 readings should be
recorded. Precautions ·
The bulb is fragile hold it gently.
Beaker is hot do not forget to
wear gloves while holding or poring hot water. ·
Stir with stirrer provided.
The results of the experiment
analysed in this section. No unusual events happened everything went as
expected. Measurements of pressure and temperature for a constant volume of gas
are recorded. From these values graph of pressure(Pa) against temperature(°C)
was created. As can be seen from the graph (1.0) relationship of pressure
against temperature is linear.
As Part of this experiment
100kPa added to the values of pressure. Graph of pressure(kPa) against
temperature(°C) was created from the values modified. As a result, the
relationship of direct proportionality can be seen from the graph (2.0). Main
reason behind adding 100kPa to pressure is to identify the absolute zero which
can be found from the x-intercept of the graph. Absolute zero of -291.9° was
obtained. Real value of absolute zero is equal to ?273.15°.
Comparison between the value
obtained from the experiment and the value which is accepted reveals
differences. Measured value of absolute zero is slightly higher than the
accepted value. Several errors could explain the differences; heat loss affects
and can change the temperature, atmospheric pressure can also affect and it can
Overall, the experiment succeeded
result of linear line graph of pressure against temperature produced which is
expected. Absolute zero found from the experiment is slightly higher than the
real value which can be taken as errors.
This section consists of
calculation made in the experiment to find out percentage certainty of how
close is the number of absolute zero comparing to the real value.