Science: Technoquest

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Q. How do safety matches work?

A. When you strike a safety match phosphorus sesquisulphide in the rough "striking" strip reacts with potassium chlorate in the head to give an initial spark. This sets off a solid state reaction in the match head that raises its temperature and starts to decompose the organic components to create a cloud of smoke. The sulphur vapour, which has a very low ignition temperature, bursts into flame and sets fire to the cloud of gas, in turn igniting the wood. Otherwise, the match would simply fizz like a sparkler.

Q. Why are some parts of the earth hotter than others?

A. A square metre of land at the Equator is being hit head-on by sunlight, but towards the poles the light is hitting it at an angle so it is catching less sunlight per square metre. There is also more atmosphere - because of the greater angle - for the light ray to pass through at higher latitudes.

Q. Why does shaking a bottle of fizzy drink make it fizz when you open it?

A. Fizzy drinks are full of carbon dioxide - the gas that makes them fizz. This gas is dissolved in the drink, like sugar in a cup of tea. However, it gradually leaks out and collects between the bottle cap and the drink, in what is called the head space. Usually, when you open a bottle of drink, this gas can escape easily and you often hear a slight psssht. When you shake a bottle, this carbon dioxide gets mixed up in the drink, forming pockets of carbon dioxide, which cannot escape easily when you open the bottle. Instead, these pockets rise rapidly to the top of the bottle, taking some of the drink with them. This drink then flows out over the top of the bottle.

Q. Why does your voice echo on long-distance phone calls?

A. During the transmission of the phone call over a satellite, not all the signal is transmitted and some of the sound is reflected from the satellite back to the phone from which it originates. This does not happen if a land line is used.

Q. Does a spirit level work in a space craft?

A. No. If there is no gravity to make the bubble float to the top, it will not work.

Q. Why is a rainbow curved?

A. Raindrops are spherical and therefore symmetrical. Light passing through a drop is diffracted like light passing through a prism, but because the drops are symmetrical, light is scattered, forming a circle of colours. If it wasn't for the ground getting in the way, we would see the whole circle.

Q. How does a Thermos flask retain heat?

A. A Thermos flask has mirrored interior walls that reflect the escaping heat back inside. It also has a vacuum partition between the walls that helps to stop heat from escaping by conduction.

Q. What is the sonic boom?

A. When something travels so fast that it goes faster than the speed of sound, it leaves its own noise behind. The sonic boom is the backlog of noise following a plane. This noise is trying to keep up with the plane but is restrained by the speed limit of sound.

These questions and answers are provided by Science Line. You can use its Dial-A-Scientist service on 0345 600444.

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