|Hands-on Physics and
Chemistry 1. Students can investigate the concept of spaces between water molecules
with this procedure. Fill a graduated cylinder or long container 3/4 full of water,
then fill to the top with alcohol. Seal the top and turn upside down enough times to mix
the two liquids. The cylinder or container will no longer be full, because the alcohol fit
in the spaces between the water molecules.
2. The gas laws can be illustrated in a nifty way by using this device: Obtain a board a meter long and 10 cm wide (even an old yardstick will do). Drill a hole in the center and one near each end. Label the end holes Pressure and Volume, and the center one Temperature, Hold Temperature constant by inserting your finger in the hole and bring Pressure down; the Volume will increase. The other relationships can be shown by pivoting at the other holes.
3. Punch a 6-9 mm hole in the lid of a gallon-size paint can and another hole on the side of the can near the bottom. Fill the can with natural gas, and turn off the gas supply to the can. Light the gas coming out of the hole in the lid. At first the flame will be tall, but will gradually burn down until it becomes fairly invisible. All this time it is drawing air into the can while it burns. When the gas/air ratio reaches the right point, the mixture in the can will explode with a loud bang and will send the lid of the can to the ceiling. NOTE: This is dramatic but safe, though you have to take care not to set the can under lights or near the students. It can make dents in ceiling tiles, also!
4. Pour enough sulfuric acid on, say, 1/4 cup of sugar to moisten it into a gooey-grainy, but not wet, mass. Stir well, Slowly it will turn the sugar yellow, then brown, then black. It will start to hiss and steam laden with excess sulfuric acid will pour forth from the black mass which will grow to several times the height of the sugar pile, Do this only in a well- ventilated room. The kids love this demo. The sulfuric acid dehydrates the sugar, driving the water off as steam, then leaving behind the black carbon.
5. Get three beakers. Put about three small crystals of potassium permanganate in the first, and fill 3/4 full with water, and stir. In the next add a small scoop of sodium thiosulfate with only enough water to barely dissolve it. In the third put in a small scoop of barium chloride, with a small amount of water to barely dissolve it. Now pour the first scarlet solution into the second beaker, turning it clear. Now pour this into the third beaker. The clear liquid will turn white.