The following investigations use the liquid crystal temperature sensing sheets that you calibrated earlier. It's necessary for the activity to have one of the liquid crystal sheets to be a color other than black (brown, tan, or green are fine, but blue means it's too hot). If neither of your liquid crystal sheets is showing a color, poke the thermostat or find another room where the temperature makes one of the liquid crystals show on scale. You will need some little pieces of the thermal sensing sheet -- one for each object. These don't need to be very big -- 1" x 1/2", for example. Please note that we will need a big piece (4" square) for the next activity.

1. Place various objects in some place where they will not be disturbed for several hours, like we did before, but this time with a small piece of thermal sensing sheet on each. Use the same objects as before -- a woolly sock, a sealed jar of water, a clean glass jar or can... . The results will be similar, too, but this way of measuring temperature is much more sensitive to small temperature variations.

• If you do detect a temperature difference between the objects (as determined by the response of the thermal sensing sheet), try to estimate how large it is.
• Touch each object with your fingers for a measured interval of time -- a few seconds and in just one place, for the first trial -- and then observe whether this causes a change in the response of the thermal sensing sheet. Repeat this sequence of observations, now touching each object for 10 seconds. Also note which objects feel warm or feel cool.

2. Hold a coin so that you are only touching part of it, for 20 or 30 seconds. Then lay it on the table and place the thermal sensing sheet on top of it. How different is the temperature of the different parts of the coin, where you were touching it and where not? Compare this to the behavior of a button or a small square of cardboard.

Check the box when you are done:  

First activity: How long does your drink stay hot?