You will need:
q 4-6 birthday candles
q Aluminium foil
q Large thin plastic bag
q 6-10 straws
q Cello tape
Hot-air balloons are fun to look at. But how can a balloon filled with hot-air float in mid-air? Try this fun experiment and find out physics behind hot-air balloons.
INSTRUCTIONS
- Firstly, take a large thin plastic bag (like a garbage bag) and measure the diameter of the opening.
- Use the diameter length as the measurement for your straw frame.
- Once you have 2 equal lengths which are the same length as your diameter, make an X shape out of the 2 lengths and stick them together in the centre.
- Fold in the sides of a 5-inch square piece of aluminium foil to make a basket and stick 4 birthday candles close to the corners. Also, stick your foil basket onto the centre of the X straw with tape.
- Attach the ends of the straws to 4 corners of the open end of the bag.
- Ask an adult to help you to hold the plastic bag up and light the candles in the foil basket carefully so as not to burn the plastic. Wait till the plastic inflates.
RESULT
The air inside the plastic bag begins to heat up, and thus expand. As the air expands, the molecules move further and further apart making them lighter. This, in turn, lifts the plastic bag into the surrounding air; it is denser than the air in the balloon.
