Mass explained to kids

Mass is a measure of the amount of matter in an object. It is measured in grams (g) in the metric system, or in ounces (oz) in the English system. The amount of space an object takes up is its volume. The more matter in an object, the more mass it has. Mass is different from weight. Weight is the force of gravity on an object. It is measured in Newtons (N) in the metric system, or in pounds (lbs) in the English system. An object with more mass will have more gravity. Most objects are a combination of different materials. The mass of an object is the sum of the masses of all the materials it is made of. For example, the mass of a wooden box is the sum of the masses of the wood, the nails, the paint, etc. The mass of an object is usually constant. However, it can change if the object gains or loses matter. For example, a person's mass will change if they eat or if they sweat. The standard unit of mass in the metric system is the kilogram (kg). The standard unit of mass in the English system is the slug.