Concepts:

Heat absorption of water or fuels

Safety:

Safety glasses

Fire extinguisher

Equipment:

• Balloon

• candle

• BBQ lighter

Preparation:

• Fill a balloon with 60 ml of water.

Demonstration Instructions

• Blow up a balloon as you normally would and tie it off.

• Light a candle and place on a table.

• Hold the balloon a foot or two above the candle and bring closer to the candle until it pops.

  • The balloon will pop ever before the candle meets the latex. There is nothing to absorb the heat.

• Repeat again with with about 60 ml of water in the balloon. Just fill the balloon with water prior to blowing up.

• Repeat moving the balloon to the flame and it will not pop even if you touch the flame to the balloon!

Observations:

• The latex allows the heat to move through the balloon and heat the water, that warm water rises and is replaced by cooler water.

• The balloon will pop when the water can no longer absorb the heat.

Learning Outcomes:

• The “Fireproof Balloon” is a simple and safe inquiry-based demonstration that challenges the students to explain why the instructor-filled balloon does not pop over a lit candle.

• The 60 mL of water placed in the instructor’s balloon prior to the demonstration will absorb sufficient heat from the candle flame such that it will not allow the latex to melt and the balloon to pop.

• You can also talk about the capacity for fuel to absorb heat from a tanker fire. It will not instantly pop or explode.

• Wikipedia states that the molar heat capacity of gasoline is 228J/mol⋅K 228J/mol⋅K (https://en.wikipedia.org/wiki/Table_of_specific_heat_capacities). This is more than twice that of liquid water ( 75.327J/mol⋅K 75.327J/mol⋅K) which is regarded as having a very high molar heat capacity.

• The fact that gasoline has a high molar heat capacity would mean that it takes a lot of heat energy to warm up gasoline to a given temperature relative to other working fluids.

Chemical Disposal:

• None

Additional Information:

Table from the Wikipeda link above.