How does water disappear when we boil it?

The water does not disappear; it simply evaporates. When we boil water, it reaches a temperature of 212 degrees Fahrenheit. The boiling water turns into a gas, which we call vapor. When the boiling water in the form of vapor comes in contact with the colder air in the room, it cools down and is once more turned into water, in the shape of tiny drops. That is why the shelf above a kettle of boiling water becomes wet. This flow of vapor is called steam. Steam is so powerful that it can be used to drive locomotives and machines!

Is gold really the natural color of goldfish?

The answer is no. The goldfish is a species of carp that the Chinese and Japanese grew in ponds over 400 years ago, in the 16th century, and on which they conducted various experiments. Over the years, this small carp lost its dark tones and began to assume a golden color.

All the various kinds of goldfish are brown during their first year, become silver in their second year, and turn gold when they become adults. The Chinese and Japanese have managed to breed various types of goldfish in all the bright colors of the rainbow.

What is a light year?

Just as we use the term “mile” as a measuring stick to measure distances, the term “gallon” to measure liquids, and the term “ounce” to measure the weight of objects, we use a special measuring stick to measure vast distances that are simply beyond the power of our imagination, such as the distances between the earth and faraway planets. This measuring stick is called a “light year” and it expresses the distance a ray of light travels in the course of a single year. If we told you that, in the course of one second, a ray of light travels about 186,000 miles, you could then perhaps understand what a vast distance a ray of light travels in the course of an entire year.

What are the differences between a frog and a toad?

The frog and the toad belong to the same family. They are very similar and many people cannot differentiate between them. The principal differences are the following:

  • Unlike frogs, toads have no teeth.
  • A toad’s legs are shorter and thicker than a frog’s.
  • The frog’s head is more pointed than the toad’s head and its skin is smooth, while the toad’s skin has many small bumps.
  • The toad’s body secretes saliva that repels would-be predators; the frog is not equipped with this defense mechanism.

Question of the Month:

This month’s question was sent by Michele, age 13, of Deal, NJ.

Dear Professor, What causes oil to burn?

Dear Michele,

Cooking oil and other oils, such as kerosene, burn because they contain combustible materials – namely, carbon and hydrogen – in large quantities. These substances unite with the oxygen in the air, and that is why oil burns.

Photos – all from Bigstock

  1. Water vapor – #3538184
  2. Goldfish – #16510247
  3. Light-year – may need to find online
  4. Frog – #3427683