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 …

Stainless steel resists rust because it contains a high proportion of chromium to carbon. Before the arrival of this alloy just before the First World War, knives and other household articles made of steel easily rusted unless very carefully dried. It was an English researcher named Harry Brearley who discovered that rust was encouraged by the carbon in steel and …

The pencil appears to bend owing to the refraction of light, or the change in direction of light when it passes through transparent materials. The light rays coming from the submerged part of the pencil are bent as they live the water. Light rays are reflected and absorbed by opaque materials such as glass, air, water, oil and certain plastics, …