QUES: Sound waves are mechanical waves. They can travel only through matter. They cannot travel through empty space. This was demonstrated in the 1600s by a scientist named Robert Boyle. Boyle placed a ticking clock in a sealed glass jar. The clock could be heard ticking through the air and glass of the jar. Then Boyle pumped the air out of the jar. The clock was still running, but the ticking could not be heard. Thats because the sound couldnt travel without air particles to transfer the sound energy. Is there any other place where sound cannot be heard? Here is a hint: is there any other place that does not have air molecules? Thats right, in space sound cannot be transferred. So can astronauts hear each other? Yes, they can, because they are in enclosed space stations or pressurized suits.In both cases, they are surrounded by air molecules. If they left their space ship and did not use their electronics, they would not be able to hear each other. Next time you watch a science fiction movie, think about this factoid. When spaceships are destroyed by hostile alien beings, there would be no sound heard. Sound waves can travel through many kinds of matter.
Do you have any questions?
MY QUESTION: Why can't you hear in the vacuum?

QUES: Josie started planning her new garden in the winter. She chose flowers and vegetables that could grow in her area. She looked through the seed magazines. She ordered the tastiest kind of each vegetable and the prettiest kind of each flower. She talked to a friend about her plans. It seemed like the snow would never melt. But Josie didn't have to wait for spring to get started. Six weeks before the last frost, Josie planted seeds indoors. The tiny seedlings pushed up through the soil and began to grow. Finally spring arrived. Each day, Josie moved the seedlings outside for a few hours so they could get used to the cooler temperatures. Josie worked in her garden, digging the soil. She added a special growing mix from the garden store to make the soil better. When everything was ready, she removed the seedlings from their trays and planted them in her garden. The warm sun and rich soil helped her vegetables and flowers grow.
Do you have any questions?
MY QUESTION: What did Josie do while she was waiting for planting season?

QUES: You know that friction also causes heat. Think about when you rub your hands together. It is friction that makes them warm. But why does this happen? Friction causes the molecules on rubbing surfaces to move faster. Faster moving particles have more heat energy. Heat from friction can be useful. Can you think of other places where you might find friction? Friction also lets you light a match. Heat from friction can also cause problems. It can cause a car to overheat. To reduce friction, oil is added to the engine. Oil coats the surfaces of moving parts. This coating of oil makes them slippery. When things are slippery there is less friction. Have you ever seen a sign that says, slippery when wet? This too has to do with friction. Water, like oil, can reduce friction. The wet surface may allow your shoes to slide more easily.
Do you have any questions?
MY QUESTION: Can oil reduce the amount of heat that is produced from the moving parts of a car?

QUES: You couldnt survive without your skin. It has many important functions. The main function of the skin is controlling what enters and leaves the body. It prevents the loss of too much water from the body. It also prevents bacteria and other microorganisms from entering the body. The skin helps maintain a constant body temperature. It keeps the body cool in two ways. Sweat from sweat glands in the skin evaporates to cool the body. Blood vessels in the skin dilate, or widen. This action increases blood flow to the body surface. This allows more heat to reach the surface. The heat is then able to radiate off the body. The opposite happens to retain body heat. Blood vessels in the skin constrict, or narrow. This decreases blood flow to the body surface. This reduces the amount of heat that reaches the surface. When this happens, less heat can be lost to the air.
Do you have any questions?
MY QUESTION:
What kind of vessels in the skin dilate to help cool the body?