Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Explain the differences between scalar and vector quantities.

### Response:
Scalar quantities have only magnitude or size, while vector quantities have both magnitude and direction. Scalar quantities can be expressed in numbers, while vector quantities require a direction to be expressed accurately. Examples of scalars include mass, temperature, and time, while examples of vectors include force, velocity, and momentum.