Make homemade hot air balloons

You’ll need

Sticky tape
Cardboard tubes
Black bin bags (preferably biodegradable)
Hairdryers (ideally, enough for one for each group)

Before you begin

Use the safety checklist to help you plan and risk assess your activity. Additional help to carry out your risk assessment, including examples can be found here. Don’t forget to make sure all young people and adults involved in the activity know how to take part safely.
Make sure you’ll have enough adult helpers. You may need some parents and carers to help if you’re short on helpers.

Creating bin bag hot air balloons

Run this activity inside to prevent plastic pollution in the environment, as all the plastic bags can be collected at the end.
Divide everyone into small groups. Explain that you're going to make bin bags into hot air balloons.
First, each group should take a bin bag and tie the handles together.
One person in each group should take the bin bag and, holding the bag by the handles, wave it from side to side or around so it fills with air.
Once it's filled with air, turn the bag upside down, so the handles are pointing towards the ground, and let go. The bag will likely float down to the ground.
Each group should talk about what happened and why they think it happened.
The bag sunk because the air inside it is cold. Cold air is heavy, so the bag sinks.

Launch the bin bag hot air balloons

Now, each group should take a black bin bag, cardboard tube (such as an empty loo roll) and a hairdryer. You may need extension leads, depending on where your plug sockets are.
Tie the bin bag handles together, so that only a small opening remains and tuck the handles inside so they’re not loose. This is like the balloon of a hot air balloon.
With adult supervision, slide a cardboard tube into the bag opening. This'll make it easier to fill the bags with air and it'll also reduce the risk of the bags melting. This is like the skirt or throat of a hot air balloon.
With adult supervision, while someone holds the bags using the hairdryer on the coolest setting, one person from each group should slowly fill the bin bag with air. The cool setting will still create warm air, but won’t melt the bags. This is like the burner of a hot air balloon.
As they fill with warm air, they bin bags should start to float and eventually fly away. As the air inside them cools, they'll sink back down to the ground.
Let each person have a go and see how high they can get the plastic bag hot air balloon to fly.

How it works

Ask everyone why the bag floated with the warm air, but not the cold air.
Explain that warm air particles are lighter than cold air particles, so warm air rises. When you blow the hot air into the bag, the air inside the bag becomes lighter than the air around it so it floats.

You could use white bin bags or plastic bags and let people decorate them.

Reflection

This activity helped everyone to understand how heat helps a hot air balloon rise. Everyone should think about the difference between hot and cold air and the other things they learned during the activity.

How did everyone find the experience of flying the bin bags? Was it easy to direct them?

How do they think pilots are able to control the direction of hot air balloons? In fact, the only thing pilots can do is steer the balloons up or down according to the of the direction the wind.

Safety

All activities must be safely managed. You must complete a thorough risk assessment and take appropriate steps to reduce risk. Use the safety checklist to help you plan and risk assess your activity. Always get approval for the activity, and have suitable supervision and an InTouch process.

Flammable items: Always take care when using flammable items, especially if you’re near fire. Always follow the manufacturer’s instructions and guidelines.
Rubbish and recycling: All items should be clean and suitable for this activity.