Your Questions
What is the purpose of yawning?
Friday, June 17th, 2011
Yawning is an involuntary respiratory reflex, which regulates the carbon dioxide and oxygen levels in the blood.
A yawn is commonly triggered either by fatigue or boredom and when a person is tired or bored the breathing is not regulated and it is shallow, and little oxygen is carried to the lungs by the oxygen-toting cardiovascular system.
Yawning elevates ones alertness, as the sudden intake of oxygen increases the heart rate, rids the lungs and the bloodstream of the carbon dioxide buildup, and forces oxygen through blood vessels in the brain, while restoring normal breathing and ventilating the lungs.
Yawning is a kind of physiological mechanism that is designed to maintain attention and regulate our breathing.
Tags: Biology, yawn
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Why is ice clear and snow white?
Thursday, September 2nd, 2010
Snow comprises huge numbers of ice crystals with lots of trapped air between them. If we could look at a single tiny ice crystal within the snow, it would look clear.
Visible light from the sun is made up of components of different wavelength (the electromagnetic spectrum as in a rainbow; red, orange, yellow, green, blue, indigo, violet). When the light hits a single ice crystal, some of it is absorbed and some reflected back; on passing through the crystal the light changes direction due to a process called refraction, as in a prism, and can be internally reflected within the crystal.
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Why does paint dry on the wall but does not harden when in the tin?
Wednesday, July 21st, 2010
There are two basic mechanisms by which paints dry on the wall.
Many modern paints are largely water-based. As we know, water readily evaporates. However, the rate of evaporation of a liquid depends on the vapour pressure of that liquid above the surface. In a sealed tin of paint, a set vapour pressure is quickly established in the small headspace in the tin and the water in the paint does not evaporate and remains in the paint. But, when painted on the wall, the water can readily evaporate to leave a dried film of solid paint components behind – there is no build-up of water vapour pressure in a confined space as there is in the tin.
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Can salt lose its saltiness?
Saturday, July 10th, 2010
Common salt comprises a very stable, simple chemical compound called sodium chloride, which has a salty flavour. As table salt, it typically also contains minor amounts of additives to keep it free-flowing.
As it is so chemically stable, sodium chloride will not lose its saltiness, even after being stored dry for many years. However, there are ways in which salt may appear to lose its saltiness.
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Why are plants green?
Friday, July 2nd, 2010
I guess there are two parts to the answer- why is green a good colour for plants to be, and how do they go about it. The key to the first part lies in how plants go about the business of living- they use light energy from the sun to drive the process of photosynthesis, which converts carbon dioxide into the sugars that they need to survive.
The fact that the leaves are green is because they are reflecting green light, and absorbing the other colours in the visible spectrum. When the light is absorbed, it is absorbed by the atoms that make up the leaves. These atoms, stuck together in molecules, gain energy from the light and this is needed to run photosynthesis. The reason plants decide to use visible light as opposed to infra-red or ultra-violet light is the same reason as why we see in the visible- there’s plenty of it around to use!
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What does “splitting the atom” mean?
Monday, June 14th, 2010
It is a very confusing term. In a sense every chemical reaction ‘splits’ atoms because it takes or adds electrons away from atoms. However the phrase would be more correct if we spoke of splitting the nucleus of an atom.
This can be done in a number of ways, but typically, it involves bombarding a substance with protons or neutrons or even entire nuclei of other atoms. Most of the particles don’t hit nuclei in the target but some do, and by interact electrically and through the strong force they can break up a nucleus.
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