The Case of the Barfy Birthday by Michele Torrey Read Free Book Online Page A

loads of fun. But when not used safely, dry ice can cause injury.
    • Always wear heavy gloves when handling dry ice—it can cause frostbite if you touch it with your bare skin. Wear safety glasses to protect your eyes from possible flying ice chips!
    • Look in your local Yellow Pages under “Dry Ice” for places that sell it. They will cut the dry ice for you.
    • Place dry ice in a plastic or Styrofoam cooler while transporting it. Store dry ice in your cooler rather than in your freezer. It will last about 24 hours.
    • Carbon-dioxide gas is heavy and can become concentrated in enclosed spaces. It can eventually replace the oxygen in a room or car, causing asphyxiation. Always leave a window cracked to allow air to flow freely throughout the room or vehicle.
    • Try not to breathe carbon-dioxide fumes. Remember, it replaces the oxygen your body needs.
    • Never taste or swallow dry ice.
    • Protect your tabletops and countertops from dry ice by using newspaper or towels. The extreme cold could cause the countertop to crack.
    • Dispose of dry ice by putting it outside in a well-ventilated container, away from small children and animals.
    Other Super-Scientific Stuff
    So . . . you’re the frozen dead sitting there with dry ice and balloons. What to do now? Try this: Place a funnel in the neck of a balloon and add a few spoonfuls of dry-ice powder. Tie the neck of the balloon. Stand back. Watch the balloon expand and then explode! (Do outdoors, far away from anything that might not like being exploded on.)
    Try this, too (great for spooky parties): In a well-ventilated room or outside, put a chunk of dry ice in a large bowl of water and see what happens.

The Scene: You and your friend have built a magnificent tree house. The biggest one in the neighborhood. The highest one for miles around. The most comfy.
    The Problem: Now that you’re snug in your tree house, you and your friend realize you’re both very, very hungry.
    You scramble down the ladder, shimmy down the wood blocks hammered into the tree trunk, and finally slide down the dangling rope until you reach the ground. Ahh, you think, food . And you load up for the trip back. (You know—cookies, cheese, sandwiches, pop, chips, etc.)
    But at the base of the tree, you stop short. Uh-oh. A terrible question comes to mind. How do you get food to your tree house when you have to climb using both your hands? You know you can’t use a backpack to carry all your food, because you will then be too heavy to pull yourself up the rope. After all, remember, you’re very, very hungry and feeling a little weak. (Besides, what about that TV set that’s next on your list of tree house musts?)
    Stumped? Try the following activity for a clue on how to make the work simple.
    MATERIALS
    • tape
    • paper cup
    • paper clip
    • handful of small rocks
    • string
    • scissors
    • 2 pulleys (available in hardware stores)
    PROCEDURE
    1. Cut a short piece of string and tape it securely to the top of the paper cup. This is your handle.
    2. Put a handful of rocks into the cup.

    3. Using another short piece of string, tie one of the pulleys to the back of a chair so that it hangs freely. This is pulley A .

    4. Cut a piece of string three times as long as the height of the chair. For example, if the height of the chair is 4 feet, cut a piece of string 12 feet long [3 x 4 = 12].
    5. Tie one end of the piece of string to the back of the chair. Thread the string through the second pulley (pulley B ) and then through pulley A .
    6. Secure the other end of the string by tying it to another piece of furniture so that your system remains tight and does not collapse.
    7. Using the paper clip as a hook, attach the cup full of rocks to pulley B .

    8. Untie the end of the string from the piece of furniture (see step #6). Pull string down to lift cup.
    9. Up, down. Up, down. Snack time!

    How Does This Work?
    Pulley A changes the direction of the force. Instead of having to lift the