Scales are the most appropriate instrument for measuring mass on Earth. Mass and weight are not necessarily the same, even though the terms are sometimes used interchangeably.
Scales come in a wide variety of styles. For example, some scales are designed so that a heavy object pulls a spring that moves an indicator, which tells the operator how much the item weighs. Other scales, such as a bathroom scale, work by using a small computer to calculate the amount of force pushing the scale down. In laboratories, most scientists use balances that allow them to compare an object with a known weight to one with an unknown weight. These types of scales often have three different arms that hold counterweights of different sizes and are called triple beam balances.
Mass refers to the amount of material in an object, whereas weight refers to the gravity affecting the object. For example, an object with 100 grams of mass does not change its mass, no matter where it is. However, the Earth's gravity pulls the object down enough to make it weigh 100 grams, but if the object were on the moon, it would weigh significantly less because the moon’s gravity is not as strong as the Earth's gravity.