Keeping Tom Warm

Objective

To investigate the thermal transfer properties of various materials.

Items you will need

several small plastic peanut butter jars with lids (baby food jars work well too) per team.
scraps of various fabrics or other flexible materials that are large enough to fully cover the sides and top of a jar. Materials could include cardboard, goose down, aluminum foil, cotton cloth, vinyl, fur, nylon, thermal underwear, wool, synthetic fiber fills taken from old winter jackets and/or old sleeping bags, paper, Mylar, Gortex and any other materials that might be interesting and that are readily available.
Six interesting materials are suggested below in the Experiment 1 section with some questions for extended experimentation.
rubber bands
2 thermometers per team
hair dryer or fan
a drill and bit (large enough to drill a hole to accommodate the thermometer through a plastic jar lid)
OR
a hammer and a large nail (large enough to punch a hole to accommodate the thermometer through a metal jar lid)

Tips and hints (always put safety first!)

Always use protective eyewear when drilling or hammering.
Handle glass thermometers very carefully. Never push or force a thermometer through a small hole. If the thermometer breaks it can cause a serious hand wound. Drill or punch the hole in the lid so that the thermometer fits through it easily.
Handle hot water carefully! Always stand up. Push chairs under or away from your desk.

Context

Dr. Hawke will be spending many hours outdoors every day during his research in Antarctica. In order to carry out his experiments as efficiently and as safely as possible it is essential that he be warm, dry, and comfortable at all times. Since moisture steals the body's heat much faster than dry air it is necessary for Tom to make sure that he is not over-dressed (which leads to increased perspiration). Over dressing has the potential to be as dangerous as under-dressing since both conditions ultimately lead to excessive body heat loss.

Consider the following ...

Tom's choice of clothing must be insulating, waterproof from the outside, very rugged and allow water vapour (from perspiration) to escape. Why are these properties important at the Antarctic? In the cold climate in which Tom must work, what are the best fabrics for him to wear? By conducting some carefully controlled experiments on various materials, come up with a class list of materials that might be suitable for Arctic and Antarctic wear.

Experts always agree that "layering" is the best way to dress when exposed to extreme environments such as the polar regions and high in the mountains.

Students can create a customized wardrobe for Tom to wear outdoors in the Antarctic starting with his socks and underwear and adding layers. They must justify each layer!

Teacher Preparation

For safety reasons teachers may wish to prepare the jars for the students in advance. Drill (for plastics) or punch (for metals) a hole in the lid of each jar. The hole should be large enough to easily insert a thermometer. Gather an assortment of materials and set out at each team work station.

Procedure

Divide you class into groups of student teams, each with three or four students. Have each team conduct the two experiments explained below using the material assigned to them. Have each team develop and carry out additional experiments (after the first two experiments have been completed) as questions about the utility of the material arise.

Compare the results obtained by each team.

Experiment 1

Insulation

Fill two jars with equal volumes of hot tap water and put the lids back on tightly. Leave one “control” jar exposed, and wrap the other jar with one of the experimental insulation materials. Completely cover the jar and lid, and secure the material with rubber bands. Punch a nail through the fabric and line it up with the hole in the lid of the jar. Measure and record the water temperature in both jars. Wait five minutes then measure and chart the change in temperature for both jars. Repeat at five minute intervals until the temperature approaches room temperature.

Basic Setup for Each Team

Due to the fact that it is possible to have a serious allergic reaction to certain foods such as peanut butter, the jar should be thoroughly washed and cleaned prior to bringing it into the classroom.

1. Plastic peanut butter jars come in two sizes, both work well for this activity, but be sure to pick only one size and stick to it! Don't mix sizes.

2. Cut a small square piece of construction paper about 2cm by 2cm. Cut an "X" in the middle and slide the thermometer through the "X". This will hold the bulb of the thermometer in the centre of the jar as shown.

3. Each team will need two jars set as shown above.

Baby food jars work well but are more fragile since they are made of glass. Also, their small size means they cool more quickly and measurements should be taken more frequently.

Some suggested samples

	Fur Experiment to see if there is a difference between fur-side-in and fur-side-out.

	Bubble padding What effect has doubling or tripling the number of layers have on the rate at which heat is lost?

	Cotton Which works better, dry cotton or wet cotton?

	"Space" blanket Aluminized side out or aluminized side in; is there a difference?

	Wool Is wet wool better or worse than dry wool?

	Foam packing sheets Some types of foam are closed cell (they don't absorb water) and some are open celled types (they do absorb water). Which is better?

Experiment 2

Wind Resistance

Hold a square of material taut. Using a hair dryer at a set distance, blow air toward one side of the material and measure the force of the air that comes through the other side. Use an air flow indicator, such as a loose, narrow strip of paper.

Extension Ideas

Today's high-tech survival gear has several layers, each designed for a different purpose. Layering is just as important to insulation as the materials used. Can your team determine the order in which these four layers should be worn in order to achieve the most efficient insulation possible? Very thick layer of a puffy, air-holding material such as down or fiber-fill. Tight material that "wicks" sweat away from the body. Windproof, waterproof, breathable thin shell. Loose, light layer. Answer 2,4,1,3