Can we collect a gas? Objectives: To know what causes gas pressure. To understand that we can collect a gas. To be able to use the particle model to explain observations.

Why does a balloon get bigger when you blow into it? Why do balloons sometimes burst on hot days? The air particles gain energy and so move faster. They collide with the rubber more frequently and the pressure inside the balloon increases. At first the rubber stretches but after a while it cannot stretch any further and the balloon bursts.

Can we collect a gas? Objectives: To know what causes gas pressure. To understand that we can collect a gas. To be able to use the particle model to explain observations.

Gases are all around us but we often can’t see them, feel them, or smell them. So how do we know they are there? Do they have any effect on the things around us? Yes – one property of gases is that they exert pressure.

Class set up apparatus together. Add the water but no chemicals.

Measure 20 cm3 of hydrochloric acid in a measuring cylinder. Pour this into a conical flask. Attach a bung and delivery tube to the conical flask. Place a filled test tube of water over the open end of the delivery tube, within a water bath. Ensure the test tube remains full once upside down. Place four marble chips into the acid and quickly replace the bung. Observe what happens to the water in the test tube.

Can we collect a gas? Objectives: To know what causes gas pressure. To understand that we can collect a gas. To be able to use the particle model to explain observations.

Questions Why do the marble chips fizz when added to the acid? What happens to the water in the test tube? Can you explain why this happens.

Cooling down a gas When you put an empty water bottle in a freezer it crumples up, why?

Cooling down a gas In a freezer, the air in the bottle cools down and the particles have less energy. The particles move more slowly and collide with the plastic less often. The air particles outside the bottle exert a higher pressure than the particles inside. The bottle collapses.

Cooling down a gas In a freezer, the air in the bottle cools down and the particles have less energy. The particles move more slowly and collide with the plastic less often. The air particles outside the bottle exert a higher pressure than the particles inside. The bottle collapses.