How does cement harden? When cement is mixed with water it hardens. This is probably due to a complicated chemical reaction between the compounds in the cement and water. There are four main compounds in cement. These are believed to become crystals with the addition...
Which is the most well-known comet? Hailey’s comet is the most famous. English astronomer, Edmond Hailey, spotted it first in 1682. He felt that he had also seen it in 1531 and 1607. He Claimed that it would appear every 76 years and predicted that...
Do snakes have hearts? The make does have a heart. It also has a backbone, a liver, a digestive system, muscles, glands, and other organs. But it does not have legs or movable eyelids. That is why it has a glassy, unblinking stare. Its eyelid...
Do deserts have cold weather? Deserts are not always hot. Most of the Arctic region is a cold desert as it has little moisture and only special life forms can survive there. The Gobi desert is hot but in winter it becomes very cold. Most...
What is granite? Granite is one of the igneous or fire-made rocks. It was formed when hot rock or molten magma slowly cooled in the earth. It is found under mountain folds where the surface rocks act like a blanket to prevent fast cooling. It...
What is cardboard and how is it made? Cardboard is actually paper but it is very thick. A slightly different machine is used to make it, though. The card, instead of being wound onto a reel at the end, is cut up into sheets. Corrugated...
What is hard water? Hard water is water in which certain minerals are dissolved. Soap will not work up a lather in hard water. Instead it forms scum. Hardness can be either temporary or permanent. The former can be removed by boiling the water. To...
What are ductile and transition metals? Ductile metals like copper can be drawn out into wires. Copper wires are good conductors of electricity. Transition metals have a high melting point. They are not very reactive. It is easy to shape them and they have myriad...
Who discovered radioactivity? It was the scientist, Becquerel, (1852-1908) who first discovered that uranium could emit rays. Marie Curie and her husband Pierre Curie investigated it further and eventually went on to share the Nobel Prize with Becquerel for discovering radioactivity.
When did mammoths become extinct? Around 10,000 years ago, the huge woolly mammoths died out. They were huge beasts. Their natural enemy was a sabre-toothed cat called Smilodon. It had fangs 15 cm long. It also became extinct with the mammoths.
