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Community College of Philadelphia

Department of Chemistry

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Lab 6: Gases
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# Laboratory Report Sheet

## Background

Matter in the gaseous state has the highest kinetic energy and many of its properties are accounted for by the Kinetic Molecular theory. In this phase, the particles of matter are widely separated and in constant random motion. As a result of this, a gas’ pressure and volume are directly related to the moles of sample and its temperature (in Kelvin). This relationship (proportionality) is expressed by the Ideal gas law (PV = nRT). In this experiment, we will explore some of the properties of gases.

Materials needed:

He (or air) filled balloon

8 oz glass

A heavy piece of cardboard

A metal can or plastic bottle with a screw- on top

## I Effect of temperature on Gas Volume and Pressure

Fill a balloon with gas (He or air) until it is firm. The volume of the balloon defines the volume of the gas. The pressure exerted by the gas is what keeps the balloon expanded and firm. The temperature of the gas is the temperature of its surroundings.

Place the balloon in the freezer compartment of you refrigerator and leave there for one (1) hour.

Make your observation on the gas’ volume (1) and pressure (2) immediately upon removing the balloon from the freezer.

Let the balloon sit for about ½ hour at room temperature and observe (3 & 4) again after the gas has warmed back up to the ambient temperature of the room.

Explain (5) why aerosol cans have a warning such as: Do not store near heat on them.

## II Demonstration of Air Pressure

Caution: Do this experiment over the sink!

Take an 8 oz glass and fill to the very top with water.

Slide a piece of heavy cardboard over the top making sure that no (or very little) air is trapped inside.

Holding the cardboard securely, turn the glass upside down and then let go of the cardboard.

Observe (6)

What is holding the cardboard in place? (7)

Which is greater, the downward pressure of the water in the glass or the upwards pressure of the air on the cardboard? (8)

Listen to the weather report. Record the barometric pressure (9) for the day.

Look up the definition of barometric pressure (10).

When bad/rainy weather systems (lows) are approaching, does the barometric pressure rise or fall (11)?

## III Demonstration of Air Pressure

Take the metal can or plastic bottle and remove the lid.

Put ¼ cup of water in the container and heat to boiling inside a larger pot of boiling water. When you no longer see steam coming from the container, screw on the lid and immediately remove the container form the heat.

Place the closed contained on the counter and observe. (12)

Explain your observations (13).

LAB 6 – Gases

I Effect of temperature on Gas Volume and Pressure

1 Observations of volume at reduced temperature

2 Observations of pressure at reduced temperature

3 Observations of volume at room temperature

4 Observations of pressure at room temperature

5 Explanation of warning label

# II Demonstration of Air Pressure

6 Observations

7 What is holding the cardboard?

8 Which pressure is greater?

9 The date __________ and barometric pressure _______________

10 Definition of barometric pressure

11 Expected change in barometric pressure

## III Demonstration of Air Pressure

12. Place the closed contained on the counter and observe.

13. Explain

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