How To Make Hot Air Balloon

Concept

When we heat the gas, its volume increases and it inflates. Let's make easy balloon by using this phenomenon.

Materials required

• Garbage bag (thin, big one is good)
• Enameled wire
• Tissue paper
• Spirit
• Adhesive tape
• Match box

Fabrication

1. The enameled wire is put on surroundings of the garbage bag with the adhesive tape.
2. Other enameled wires are put in four places as shown in figure.
3. Tissue paper is held to  the center of wire and put spirit a little.
4. Top of the bag is held and the tissue paper is put on fire. Be careful not to fire the bag.
5. The bag inflates and goes up.

Precaution

The experiment does not give promising result in summer time or in elevated temperature as the temperature difference decreases, winter season is the most better time for this activity. Do try to fly you balloons in a windless place as well as they will be light in weight.

Science

This experiment is simple. But students can make sure three phenomena when they think why the balloon can go up in the air.

1. The movement of the gas molecules become faster at the high temperature. So the volume of gas grows. It is Charles' Law. Students can see the garbage bag inflation.
2. When the volume of the gas grows, the mass for each unit volume becomes small and the density becomes small.

3. Buoyancy of gas inside the bag becomes more than gravity when the density of in it is smaller than that of surrounding gas. And the balloon goes up.

Application

The bag goes up for a while even if warm air is sent to the inside with the hair drier instead of using the fire.