Hobbies And Interests
Opposites Attract: Static Electricity
In this experiment, students learn about the nature of static electricity and the role that negatively and positively charged particles play in generating it. Students first rub two inflated balloons against a piece of woolen fabric one at a time. Then, they try pressing the balloons together and find that the balloons repel one another. The balloons have both taken electrons from the fabric and are therefore both negatively charged and unattracted to one another. Next, students rub a balloon against their hair and slowly pull it away from their heads. Looking around the room, they will notice that the balloons attract their classmates' hair; in the process of rubbing the balloons against their hair, static electricity was generated. The balloons removed electrons from their hair, causing their hair to become positively charged and the balloons to become negatively charged. Since their hair and the balloons have opposite charges, they attract one another.
Air Pressure: How a Straw Works
With this experiment, students learn about air pressure as it relates to the workings of a drinking straw. Students insert a drinking straw into a glass of water dyed with food coloring to make it more easily visible through the straw. After sucking some liquid into the straw, they quickly cover the top of the straw with a finger. The result is that the liquid remains inside the straw rather than spilling back into the glass. Blocking the top hole has decreased the air pressure pressing against the liquid through the top of the straw. Consequently, the air pressure on the bottom of the straw is greater than the air pressure coming from above, and the air pressure from below works to keep the liquid inside the straw.
Heat Absorption: Colors
This experiment teaches students why adults often advise them against wearing darker colors on hot summer days. Students use a rubber band to secure a sheet of black construction paper around a glass jar and a sheet of white construction paper around an identical glass jar. Then, they fill each jar with the same amount of water and allow the jars to sit out in the sun for a few hours. Upon returning to take the temperature of the water in each jar with a thermometer, they discover that the water in the jar with the black paper is warmer than the water in the jar with the white paper. Lighter surfaces, such as the white paper, reflect more light, while darker substances, such as the black paper, absorb more light. Therefore, the water in the glass with the white paper remained cooler.
Air Molecules: How Heat Yields Air Expansion
This experiment demonstrates the role of heat in air expansion. Students stretch a balloon around the neck of an empty glass jar. With the help of an adult, they hold a flame beneath the jar and watch as the balloon begins to inflate. The application of the heat causes the air molecules inside the jar to move farther apart. Therefore, the air begins to occupy more space and must seep into the balloon since it can no longer fit inside the jar.