The Case of the Terrible T. Rex (8 page)

(CAUTION: Look over your shoulder now and then, just in case a werewolf is lurking. Don’t let their howling unnerve you …)

PROCEDURE

This activity works best outside on a cool day or in the coolest part of the day. Do not do this activity if there is a breeze.

1.   Reduce the size of the opening of the plastic bag (tent) so that it will act like the mouth of a hot air balloon. To do so, gather together small sections of the opening and firmly secure each section with a paper clip. When finished, the mouth of the plastic bag (tent) should be about twice the size of your fist.

2.   Tie a long piece of fishing line to one of the paper clips so that your bag (tent) is retrievable.

3.   Hold on to the opening of the plastic bag (tent) with one hand. Insert the hair dryer into the opening and turn it on. (Heat should be on
high.
Be careful that you do not burn yourself or melt the bag.)

4.   Once the bag (tent) is filled with hot air, turn off the hair dryer, hold on to the loose end of the fishing line, and release the bag (tent).

5.   Watch in amazement as the bag (tent) floats up, up, and away!

6.   Now determine what caused the bag (tent) to float. Werewolves? Hot air? Hmm … jot your conclusions in your lab notebook.

How does this work?

Air is composed of molecules. When air is cold, the molecules are close together and vibrate very little, making cold air dense and heavy.

In hot air, however, the molecules vibrate quickly, bumping into one another like popping corn. Because each molecule needs more space to move, hot air expands, making hot air lighter and less dense than cold air.

Conclusion? Hot air tents are lighter than the surrounding cold air environment, so they float up, up, and away! (FYI: Werewolves, besides being shifty and dangerous creatures, are quite dense and therefore must stay on the ground.)

I
t’s tragic, quite tragic indeed. The water is polluted. The fish are counting on you to save the day! In this activity, you will test the pH of various water samples, just like Nell did. You will determine which water is safe for the fish and which water needs to be cleaned up, pronto!

MATERIALS

•   4 large baby-food jars with lids

•   masking tape

•   permanent marker

•   measuring spoons

•   tap water

•   white vinegar

•   baking soda

•   water from a local river, stream, or lake

•   purple cabbage

•   pitcher

•   measuring cup

•   white coffee filters

•   coffee strainer