Define area and its SI unit. Explain why water forms a concave meniscus and describe how a siphon works.

1. a) Area is the measure of the extent of a surface or the amount of space a two-dimensional shape covers.

1. b) The SI unit of area is the square metre ($\text{m}^2$).

2. Water forms a concave meniscus in a glass tube because the adhesive forces between water molecules and the glass molecules are stronger than the cohesive forces between the water molecules themselves. This causes the water to climb up the sides of the glass tube.

3. The process shown is a siphon.