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Q Is it true that Venus rotates about the Sun in the opposite direction to all the other planets?

A No. Venus revolves around the Sun in the same way as the other eight planets. What is different about Venus is its rotation about its axis, which is backwards in relation to other planets. This is known as a retrograde revolution. On Venus, the Sun rises in the west and sets in the east.

Q If an electric kettle is turned on, there is a sizzling noise which then dies away. Why?

A When a kettle is turned on, the water around the element becomes very hot while the rest is still cool. Bubbles form and rise from the element, but when they hit the cold water they collapse. The noise of this sudden implosion causes the hiss, which dies away as the rest of the water approaches the same temperature.

Q Can we ever reach absolute zero Kelvin?

A Temperature is the vibration of molecules or atoms in a material. In non-quantum physics, all random vibrations disappear. Although in theory it is possible to reach this point, in practice heat energy would leak into the material from outside. In quantum mechanics, however, it would be impossible even in principle to reach a state where atoms are stationary.

Q Why is mercury a liquid?

A Everything exists in three states: solid, liquid and gas. A solid will turn to a liquid at its melting point. The liquid will turn to a gas at its boiling point. Water melts at 0oC and boils at 100oC so it is a liquid at room temperature. The differences in melting and boiling points depend on the how strongly the atoms are held together. Mercury has relatively weak bonds for a metal and melts at -39oC, so it is a liquid at room temperature.

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