writting definitions by using which & who

1. a thermometer: is an instrument which is used to measure temperature.

2. a chemist: is a scientist who studies chemistry and does research in chemistry.

3. mercury: is an element which is metallic and liquid at normal temperature and pressure.

4. chemistry: is a science which is concerned with composition, structure, properties and reactions.

5. an elephant: is a large land animal which has a thick skin, four legs, a trunk and tusks.

6. a physicist: is a scientist who studies and does research in physics.

7. physics: is a science which is concerned with matter and energy and their interactions.

8. a carpenter: is a person who constructs and repairs wooden objects.

9. a fuel: is a substance which supplies energy when it is burned.

10. oxygen is a nonmetallic element which has the atomic number 8 and an atomic weight of 14.9994.

11. geologists: are people who study the rocks and soil which make up the earth and the way they have changed since the earth was formed.

if any body does not know how define just ask