In our last lesson, we began to explore pressure. We observed how changing both the number of particles and volume affected pressure. We saw that the number of gas particle and pressure have a direct relationship, while volume and pressure have an indirect (or inverse) relationship.

In this lesson, we will examine the effect of temperature on pressure.

We will also be introduced to a new temperature scale in which we will record the temperature of a gas.

Below is a video of your instructor measuring the pressure of a sample of room temperature gas inside a flask. Pressure will be measured in units called kiloPascals (kPa). Watch the video and then answer the questions below.

Now your instructor will measure the pressure of a sample of gas inside a flask when the flask in submerged in both hot water and cold water. Pressure will be measured in units called kiloPascals (kPa). Complete the data table below after you view the video.

In order to analyze your acquired data, you will use Google Sheets. A template for Google Sheets has been created for you and can be found on Google Classroom.

1. Notice the data table has already been created for you. Enter the temperature data at room temperature.
2. Now enter temperature data for both cold/ice water and hot water.
3. Now enter pressure data for all temperatures. A graph should appear in a box that previously said "No data".
4. Add a trendline to the graph by opening the chart editor and clicking on “series” and clicking the “add trendline” box. The default trendline is linear which is what you want.
5. Then answer the questions below.

The graph you created on the last page should look very similar to the one shown below.

Notice the approximate temperature where pressure equals zero is -273 ^oC, this is no coincidence. -273 ^oC = 0 Kelvin, which is also known as absolute zero.

Absolute zero is the lowest theoretical temperature possible;  it is the temperature at which all particles cease movement. If particles are not moving, they cannot hit the walls of their container and therefore also have no pressure.

The Kelvin temperature scale is used when describing gases.  This is because the Kelvin scale is directly proportional to the kinetic energy of the gas particles. Thus, 0 K (absolute zero) means no kinetic energy. If particles have no kinetic energy, then they are not moving and cannot cause any pressure inside their container. This is why absolute zero (0 K) is also where pressure equals zero.

This temperature scale will become especially important when we begin gas calculations. Gas variable relationships we have explored can be expressed as mathematical equations. For example, as temperature decreases, so does volume, so if temperature is cut in half, volume will also be cut in half. This mathematical relationship will only hold true if the temperature is in Kelvin.

The Kelvin scale has no negative temperature as there can be no negative volumes, no negative pressures, and no negative number of particles.

The formulas to convert from the Celsius scale to Kelvin and back again are shown below. You will need them to complete the questions at the bottom of the page.

Celsius to Kelvin: K = ^oC + 273

Kelvin to Celsius: ^oC = K - 273