The hardest natural substance found on Earth is:

Sound cannot travel through:

The energy released when a substance burns in the presence of oxygen is called:

The process by which plants lose water in the form of vapor is called:

The chemical formula for common table salt is:

The pH value of pure water at room temperature is:

Which of these is not a renewable source of energy?

Which vitamin is produced in human skin upon exposure to sunlight?

The study of heredity and variation in living organisms is called:

Rusting of iron is an example of which type of reaction?

Which gas is used in the preparation of soft drinks to add fizz?