Mass is a measurement that describes how much matter there is in an object. It is typically measured in kilograms (kg).

Mass is measured with a balance, which makes use of the acceleration due to gravity. This is an essential measure in science and engineering.

## Weight

Mass is a measure of the amount of matter in an object. It is directly related to the number and type of atoms that make up the object.

Weight is a measure of the force exerted by gravity on an object. It is also a vector quantity, meaning that it describes how an object’s position changes due to the acceleration of gravity at a particular location.

The International System of Units defines the kilogram (kilograms or kg) as the basic unit of mass. Commonly encountered multiples and sub-multiples of mass include the metric tonne (one metric tonne is equal to one thousand kilograms), and the gram.

The law of conservation of mass states that the total mass of a closed system must remain constant over time. This principle is used in mass measurement to keep the units of mass precise.

## Force

Force is a push or pull that affects an object’s shape, size, speed, or motion. Forces can also change the direction of an object’s motion.

Unless acted upon, objects will tend to stay put or move in a straight line. That is, if an air hockey puck is left to its own devices it will keep sliding on the same path forever.

In physics, forces can be classified into contact and action-at-distance forces. Direct contact forces include friction and air resistance.

The unit of force in the International System of Units (SI) is the newton (N). It is defined as the amount of force needed to accelerate a kilogram of mass by one meter per second squared.

## Density

Density is a physical property of matter that expresses the relationship of mass to volume. It is measured in units of grams per cubic centimetre (g/cm3), milliliters per milliliter (ml/ml), and kilograms per cubic metre (kg/m3).

Density varies from element to element on the periodic table and is also affected by environmental conditions including temperature and atmospheric pressure. It is generally less dense in liquids and gases because the particles are more free to move around than in solids, which have tightly packed particles.

Density is used to determine the weight of objects, such as an anchor or helium balloon, and to identify different materials. It is also used in pipe design, shipbuilding, and weight distribution in an aeroplane.

## Volume

Volume is a measure of the amount of space occupied by a solid, liquid or gas. It can be expressed in a variety of units, including liters (L), cubic metres (m3), gallons, milliliters and teaspoons.

It is commonly used in physical sciences like chemistry, where it is necessary to measure samples with high precision. The standard unit of volume is the cubic meter (m3), but in practice it is most often measured in millilitres (mL).

For simple three-dimensional shapes, volume can be easily calculated using a formula. A box is a common example, and you can calculate its volume by multiplying its length times width and then its height.

A cylinder is another common shape. To find the volume of a cylinder, multiply its height by the area of its base.