Physics IGCSE question please help me?

Your answer to Q1 is excellent.

Q2. Correct . A bit brief though . Are you expected to know the   mechanism that causes the screen coating of fluorescent chemicals to flash when hit by a high speed electron? Probably not., so just leave your answer.

Q3. The North pole of a magnet is the bit of  the magnet that is attracted northwards by the Earth's magnetic field ( when the magnet is suspended in such a way that it is free to turn ). Since the North pole of the magnet is attracted towards he South pole of any other magnet, this means that close to the     Earth's North Geographic Pole, there must be a South Magnetic Pole.

Q4 Yes - the molecules of a hot solid are vibrating with greater speed and they are ( usually ) slightly further apart. Which means that hot objects have expanded a little. ( Not all heated objects expand - water, when heated from 0˚C to 4 ˚C , will actually contract.... and this is very important for the survival of life )

Q5 The board has a much greater   surface area than the area of the    4 feet of the    chair and so , with the same weight of  person sitting on the  chair, the pressure exerted by the board on the ground will be far less than  the pressure from the chair legs .

You have it all right really ;-)