Gas Quizlet: Packet Questions

The independent variable in both experiments is moles of gas. However, in experiment A, pressure is the dependent variable (nonflexible container), while in experiment C, volume is the dependent vari- able (flexible container).

Compare Experiment A of Model 1 with Experiment C of Model 2. How are these two experiments similar and how are they different in terms of variables?

The independent variable in both experiments is temperature. However, in experiment B, pressure is the dependent variable (nonflexible container) and in experiment D, volume is the dependent variable (flexible container).

Compare Experiment B of Model 1 with Experiment D of Model 2. How are these two experiments similar and how are they different in terms of variables?

Experiment C Independent Variable: Moles or number of molecules Dependent Variable: Volume Controlled Variables: Temperature and external pressure Experiment D Independent Variable: Temperature Dependent Variable: Volume Controlled Variables: Moles or number of molecules, external pressure Experiment E Independent Variable: External Pressure Dependent Variable: Volume Controlled Variable: Moles or number of molecules, temperature

Complete the following table for the three experiments in Model 2.

Experiment A: Direct or inverse proportion? Direct Algebraic Expression: P=km Experiment B: Direct or Inverse Proportion? Direct Algabraic Expression? P=kT

For each experiment in Model 1, determine the relationship between the independent and depen- dent variables, and write an algebraic expression for the relationship using variables that relate to the experiment (Pinternal, V, T or n). Use k as a proportionality constant in each equation.

Experiment C Direct or Inverse proportion? Direct Algebraic Expression: V=km Experiment D Direct or Inverse proportion? Direct Algebraic Expression: V=kT Experiment E Direct or Inverse proportion? Inverse Algebraic Expression: V=k/p

For each experiment in Model 2, determine the relationship between the independent and dependent variables, and write an algebraic expression for the relationship using variables that relate to those in the experiment (Pinternal, V, T or n). Use k as a proportionality constant in each equation.

No intermolecular attractions (no interactions between molecules) Molecules are always in motion. No energy loss in collisions The molecules are distributed randomly (collisions are evenly distributed) The volume taken up by the gas is negligible

Gas reminders

No—as the external pressure is decreased, there would be no change in the volume of gas or the internal pressure because the nonflexible container would contain the gas.

If Experiment E of Model 2 were done in a nonflexible container, would there be any change to the internal pressure of the flask when the external pressure was reduced? Explain.

Temperature is related to average kinetic energy, and thus to the length of the arrows.

In Model 1, the length of the arrows represents the average kinetic energy of the molecules in that sample. Which gas variable (Pinternal, V, T or n) is most closely related to the length of the arrows in Model 1?

A gas atom or molecule.

In Model 1, what does a dot represent?

Latex and rubber are flexible materials.

MODEL 2: 12. Consider the gas samples in Model 2. a. Name two materials that the containers in Model 2 could be made from that would ensure that they were "flexible"?

Glass and metal are nonflexible.

Name two materials that the containers in Model 1 could be made from that would ensure that they were "nonflexible?"

Controlling the volume requires a nonflexible container because any time the internal pressure is dif- ferent from the external pressure the container would expand or contract if it were flexible. You need a nonflexible container to contain a gas with an internal pressure that differs from the external pressure.

Of the variables that were controlled in both Experiment A and Experiment B in Model 1, one requires a nonflexible container. Name this variable, and explain why a nonflexible container is necessary. In your answer, consider the external and internal pressure data given in Model 1.

As more gas molecules were added, the internal pressure would increase at first. That would push the sides of the flexible container outward, causing the volume to expand until the pressure equalized.

Predict what would happen to the volume and internal pressure in Experiment A of Model 1 if a flexible container were used.

As the gas molecules are heated, the internal pressure would increase at first. That would push the sides of the flexible container outward, causing the volume to expand until the pressure equalized.

Predict what would happen to the volume and internal pressure in Experiment B of Model 1 if a flexible container were used.

As more gas molecules are added, they hit more often, increasing the internal pressure of the gas. This pushes on the sides of the container increasing the volume. As the volume increases, the gas molecules hit less often, reducing the internal pressure to the point that it matches the external pressure again.

Provide a molecular level explanation for the increase in volume among the balloons in Experi- ment C. (How often and/or how hard are the molecules hitting the sides of the container?)

As the gas molecules are heated, they hit more often and harder increasing the internal pressure of the gas. This pushes on the sides of the container increasing the volume. As the volume increases, the gas molecules hit less often, reducing the internal pressure to the point that it matches the external pressure again.

Provide a molecular level explanation for the increase in volume among the balloons in Experiment D.

As the external pressure is decreased, the higher internal pressure pushes on the sides of the container. As the volume increases, the gas molecules hit less often, reducing the internal pressure to the point that it matches the external pressure again.

Provide a molecular level explanation for the increase in volume among the balloons in Experiment E.

As more molecules are added to a flask, they hit the sides of the flask more often and increase the pressure.

Provide a molecular-level explanation for the increase in pressure observed among the flasks of Experiment A.

As the gas molecules are heated, their average kinetic energy increases. They hit the sides of the container more often and also harder, which increases the pressure.

Provide a molecular-level explanation for the increase in pressure observed among the flasks of Experiment B.

How hard the molecules hit and how often they hit the sides of the container.

Read This! Pressure is caused by molecules hitting the sides of a container or other objects. The pressure changes when the molecules change how often or how hard they hit. A nonflexible container is needed if the gas sample is going to have an internal pressure that is different from the external pressure. If a flexible con- tainer is used, the internal pressure and external pressure will always be the same because they are both pushing on the sides of the container equally. If either the internal or external pressure changes, the flex- ible container walls will adjust in size until the pressures are equal again. Name the two factors related to molecular movement that influence the pressure of a gas.

1.) middle 2.) Lowest temperature 3.) Higest temperature

The three samples of identical gas molecules below all have the same internal pressure. Rank the samples from lowest temperature to highest temperature, and add arrows of appropriate size to illustrate the average kinetic energy of the molecules in the samples.

The internal pressure is equal to the external pressure.

What is always true for the external and internal pressures of a gas in a flexible container?