Going Through Term 3 Common Test

3 Thoughts:
1) I have learnt that mercury is a silvery metal which is a liqud at room temperature. Mercury is a good conductor of both heat and electricity. Mercury will become a solid when it is below its melting point(very low) while it will become a colourless gas when it is above its boling point(very high).
2) I have learnt that for filtration to work properly, the size of the holes on the filter paper must be very small so that insoluble substances, which are very small in size, such as pepper can be collected as the residue on the filter paper.
3) I have also learnt that if you want to get a mixture which has a very low melting point and a very high boiling point, the substances that are mixed together must also have the properties(low melting point and high boiling point).

2 Questions:
1) When we want to get a mixture which has low melting point and high boiling point, must all the substances which are mixed together have those properties(low melting point and high boiling point)? Or just one substance that has those properties will be enough?
2) Is the colour of the mercury different when it is at the solid state and at the liquid state?

1 Useful application:
1) We know that mercury is a liquid at room temperature, thus we must be careful when handling with thermometers as mercury is found in them. When we are not careful and drop the thermometer, the thermometer will crack and the mercury in it will flow out. It will be very difficult for us to collect back the mercury which is scattered on the floor as it is in the liquid state but not in the solid state and mercury is also poisonous. Hence, we cannot touch it with our bare hands.