"Air Balloons" Return to list of pracs

Aim: This activity is used to demonstrate how air balloons work.

Equipment: The equipment includes...  

• 16 pieces of tissue paper;
• clag;
• scissors;
• hair dryer;
• string.

Method: Place 4 pieces of tissue on the ground and glue them together along their longest edges. Repeat this process for each set of 4 pieces of tissue. You will end up with 4 large sheets of tissue paper (each of the single sheets are glued along their longest sides). Each of these large sheets form the four sides of the balloon.

Place one large piece on the ground and place another directly on top. Folded the top piece down the centre from top to bottom (down its full length) facing to the left. Place another on top and folded this piece down the centre from top to bottom (down its full length) but facing to the right. Place the final piece on top.The diagram is below...

Lay the final piece on top of all three large sheets. Draw out the balloon shape and cut out all four layers simultaneously. Then glue all outer edges except the base. Place masking tape around the hole at the base and strengthen the top of the balloon with masking tape. When dry use the hari dryer to heat inside the base hole to make it rise.

Background knowledge: Balloons rise in the air if the air on the inside is less dense than the air around the outside. Density refers to the amount of matter for the same volume of material. Two materials that are the same size and shape but are different weights have different densities. The heavier shape is termed "more dense" than the other. There is more mass per volume for one shape compared to the other.

In air balloons, they burn gas at the base of large hot air balloons to heat the air. This makes the air inside hot and expands the gaps between the air particles. This makes the air less dense than the air outside the balloon. This results in low pressure on the inside and higher pressure on the outside. Just as warm air rises the balloon in forced upwards into the air up to a point in the sky where the weight of the balloon is equal to the force upwards created by this difference in air pressure inside and outside the balloon. To come down, simply turn off the heater for a short time and then air cools, gets more dense and less force (air pressure) results.