# The Fire-Proof Cup

## Objective

To investigate the specific heat properties of water by comparing the flammability of an ordinary paper cup filled with water to one not filled with water.

## Difficulty

Procedure: Easy

Concept: Medium

This experiment has potential safety hazards, please be careful and check out our safety guide.

## Concept

We all know that paper, and paper cups for that matter, easily burn. However, if you fill a paper cup with water it will not ignite in normal circumstances. This is because the heat from a lighter or the bunsen burner will be absorbed by both the paper in the cup and the water inside the cup. The specific heat capacity of water allows it to absorb surrounding heat quite well, thereby protecting its paper container. How high are the specific heat capacities of other liquids?

## Materials

• Paper cups
• Lighter or bunsen burner
• Thermometer
• Tongs
• Water
• One or more other liquid

# CAUTION

• Be careful around the open flame
• Always hold the paper cups with tongs while exposing them to a flame
• Have a fire extinguisher nearby for any accidents
• Do not test any flammable liquids (e.g. alcohols or lighter fluid)
• Mercury thermometers are not recommended, but if you must use one be very careful not to overheat or break it.
• Mercury is very hazardous and should never be touched by hand.

## Hypothesis

Make predictions regarding the specific heat of water versus other liquids (e.g. honey or shampoo). In other words, you should predict that one will heat up faster than the others when exposed to the lighter or the bunsen burner.

## Procedure

• Obtain all of the materials you need to use, move outside or to a well ventilated room, and put on your safety goggles.
• Hold one paper cup with the tongs, place the flame source underneath it and light it. Do this to make sure that the heat source is strong enough to make the cups burn.
• Fill a cup with a measured amount of water and record its temperature.
• Hold the cup with the tongs and place the flame source underneath the cup for a set amount of time. When you remove it from the flame, quickly recheck its temperature.
• Repeat steps 3 and 4 for each liquid you are going to test. Be sure to use the same amount of each liquid.
• You may want to perform a few trials with each liquid in order to find an average.

## Results

After you have finished all of the trials for each of your liquids, compute the average temperature changes for each liquid. Compare these temperature increases. Which liquid or liquids resulted in very high changes to temperature? Which liquids resulted in little change to temperature? Did the paper cup burn despite the use of a particular liquid? What do these answers mean about the liquid's specific heat capacity - its ability to absorb surrounding heat? Why do the results differ for each of the liquids? Try to explain this using the chemical properties of hydrogen bonds.

## Extension

Can you guess how certain other liquids would behave in this experiment? How would changing the amount of liquid in the cups affect the results? What does this mean about the relationship between large bodies of water and climate?