Power is measured in watts. This can mean either the power that something produces as it works, or the power that is needed to drive something. A watt is not a very big unit of power. Powerful machines are therefore graded in kilowatts(KW) or megawatts(MW). A kilowatts is 1,000 watts and a megawatt is 1,000,000 watts. The watt is named …

Calcite is a mineral which forms most of a common rock called limestone. A pure form of calcite, called Iceland spar, is transparent. If you placed a piece of it on this page, you would see two images of every word. This unusual feature is called double refraction.

The whales are a large group of aquatic animals that very in size from about 4 feet in length to nearly 100 feet. During the evolution of mammals tens of millions of years ago one group returned to live in water. These mammals became streamlined in shape, developed a powerful tail and front limbs for use as steering fins, and …

The earth is surrounded by air, which is unevenly heated by the sun. The equator is surrounded with hot air, cold air surrounds the North and South poles. Warm air rises and cold air sinks, and this movement creates wind. Movement in one place causes movement in another, like if we pour a cup of water into a full bucket, …

The holes in a piece of bread are made by bubbles of gas. In bread-making flour and water are mixed to form a dough. Then a small amount of yeast is added to the mixture. Yeast is type of fungus which grows very quickly when it is warm and damp. While growing, it gives off a gas which bubbles up …

Have you ever wondered why hens don’t break their eggs when they sit on them? The secret lies in the shape of the egg. An egg is a great example of nature’s excellent skills in packing. If you squeeze the ends of an egg between the palms of your hands, it won’t break. However, if you squeeze it in the …

The green color in grass-and in most other plants-comes from chloroplast within the cells, each of which contains four different colors or pigments. These are: chlorophyll a, which is the strongest and is blue-green; chlorophyll b, which is yellow-green; xantophyll, which is yellow; and carotene, which is orange and gives carrots their bright color. Grass goes from light green in …

It is the sulphur in the air, which often comes from coal-gas used for cooking and heating, that causes silver to tarnish or blacken. Silver combines with sulphur to form the black silver sulphide sometimes found on forks and spoons which have been in contact with egg folk. Silver is a precious metal which the Greeks called shining. In spite …

Nectar is taken from a flower by the bee and carried in the honey sac back to the hive. It is transformed into honey by enzymes produced in the honey sac, which convert the natural sucrose (a complex sugar) in the nectar into fructose and glucose (simple sugar). Fructose is the sugar that makes honey sweet.

This is due to the pull of the earth’s gravity. If there were no gravity the stone would remain in the air. When the stone is thrown into the air, a force is applied to it which is greater than the pull of gravity. But as it rises higher the force becomes weaker until the stone reaches a point where …