6.4 Activities
A bottle of cloud
Make a cloud in a bottle to see how clouds form.
One of the challenges when simulating the weather in a climate model is getting the clouds right. Clouds influence the temperature on the ground, and their formation depends on a few key ingredients. This can be demonstrated by a simple experiment.
Materials:
- Clear plastic soft drink bottle
- Water
- Matches

First, remove the label from a large, clear plastic soft drink bottle, and add a small amount of cold water. Screw on the cap, shake the bottle, and squeeze and release it a few times.
Nothing happens, as not all the ingredients are there.
Next, open the bottle and drop a lit match into it (the match will go out when it hits the water). Screw on the cap, squeeze the bottle and then shake it again.
The bottle will appear to fill up with smoke. Squeeze and release the bottle again a few times, and it will become clear that it is not smoke, but fog (or a cloud in a bottle).

Releasing the squeezed bottle increases the volume inside. This decreases the pressure, which decreases the temperature inside the bottle. When water condenses, the droplets may form clouds. Particles in the air help the droplets form. In fact, without tiny particles in the air, clouds would not form at all. Here, the drops form on the smoke particles.
This activity shows the ingredients for a cloud include water vapour in the air, a drop in temperature, and a surface on which to form. It also demonstrates that high pressure (squeezing the bottle) leads to clear skies and low pressure (releasing the bottle) leads to cloudy skies. Importantly, it shows that the addition of small pollutants to the atmosphere can have an impact on the formation of clouds, and hence the climate.
Discussion questions:
- What are three conditions required for a cloud to form?
- List three causes for a drop in temperature in the atmosphere.
- Conduct some online research to find out how climate change affects cloud formation.
A bottle of greenhouse gas
TEACHER RESOURCE!
See how carbon dioxide absorbs heat and increases the air temperature.

Materials:
- 2 thermometers
- 2 large plastic drink bottles (1.25 litres each)
- Baking soda
- Vinegar
- Tablespoon
- Heat-emitting lamp
- Allow two thermometers to reach room temperature. Measure the air temperature and make a note of each recording.
- Add two tablespoons of baking soda and 60ml of vinegar to one of the bottles. Leave the other bottle empty.
- Put a thermometer in each bottle.
- Place a powerful lamp a few centimetres away from the bottles, at an equal distance. Choose a lamp that emits heat – like a sun lamp or one with an old-fashioned globe.
- After a few minutes, check the temperature of each bottle.

The lamps represent the Sun heating the Earth. The baking soda and vinegar react to form bubbles of carbon dioxide, so this bottle represents the Earth’s atmosphere with a greenhouse effect. The carbon dioxide is about 50% more dense than air, so it will stay in the bottle. The temperature of the bottle containing carbon dioxide should be warmer, as the carbon dioxide absorbs heat. The empty bottle does not have any carbon dioxide (other than the small amount in the air), so the heat escapes.
Discussion questions:
- What is the difference in temperature between the two bottles?
- What is the reason for the temperature difference?
- Conduct online research to find the approximate concentration of carbon dioxide in the Earth’s atmosphere today. Has this concentration changed over time?
- What do you think are the main impacts of a warmer climate on the ACT? What are the impacts on people? What are the impacts on the environment?
A bowl of sea level rise
The world’s sea level (the height of the Earth’s seas and oceans) has risen by about 20cm in the past 100 years. It has been rising even faster in recent years. This may make living by the coast and on small islands impossible in the future.
Global warming and melting ice cause the sea level to rise. But what type of ice? Is it the ice from icebergs floating in the sea, or the ice on land? Let’s find out.
Experiment 1: Do melting icebergs cause sea level rise?
Materials:
- Bowl of water
- Ice cubes
- Masking tape
Add water to a bowl until it is about half full (if you don’t have a bowl, you can use a large glass). Then add 10 ice cubes, or just enough to make the water rise nearly to the top of the bowl. Try not to spill any water – it might be a good idea to do this in the sink. Mark the water level with a piece of tape, then leave the bowl until all the ice has melted.
Did the melting ice cause the water level to rise? Or did it stay the same?

Experiment 2: Does melting ice on land cause sea level rise?
Materials:
- Bowl of water
- Ice cubes or ice block
- Mug
Place a mug upside down in a bowl. Add water until it nearly reaches the base of the upturned mug. Balance around 10 ice cubes (or as many as you can fit) on the top of the mug. You could also use one larger piece of ice that can be balanced on the mug. Leave the bowl until all the ice has melted. Did the melting ice cause the water level to rise? Or did it stay the same?

In experiment 1, the water level should have stayed the same. So, the water shouldn’t have overflowed. When ice in water melts, it merely changes form – from solid water to liquid water. The ice displaces the water so, when it melts, the resulting water fills the space formerly taken up by the ice.
In experiment 2, the water level should have risen. This is because the melted ice has increased the amount of water in the bowl.
Floating frozen water (like icebergs in the Arctic region) would not raise the sea level if it melted. However, the ice sheets of Antarctica and Greenland mostly lie above land, and they contain huge amounts of frozen water. So, if they melted the water would run into the oceans, raising the global sea level.
Sea level is also rising as our oceans get warmer, because water expands in volume as it warms. About a third of the observed rise in sea level is due to ocean warming. The rest is due to melting land ice and changes in the amount of water stored on the land. Just as your melting ice cubes didn’t cause the bowl of water to overflow, none of the rise in sea level is due to melting icebergs.
Discussion questions:
- Why did the positioning of the ice in the experiment influence changes in the level of the water in the bowl?
- What are three causes of sea level rise in the oceans?
- What do you think are the main impacts of a sea level rise? What are the impacts on people? What are the impacts on the environment?