In my opinion, Weighing is the best method of measuring the quantity of matter in any form- solid, liquid or gaseous. Liquids can be measured by volume but volume changes with temperature. Some material's length change with temperature. But nothing can affect mass or weight.

Mass and weight are not same.

Mass is how heavy an object is without gravity or how much matter an object has. SI unit for mass is kilograms.

Weight is the force of gravity on the object or the product of mass and acceleration of gravity.

Weight = mass x gravity
SI unit for weight is Newton.

1 kilogram (mass) weighs 9.8 Newtons under standard conditions on the Earth's surface. However, kilogram is the most commonly used unit for weight for commercial purposes.

1000 grams = 1 Kilogram
100 kilograms = 1 Quintal
1000 kilograms = 1 Tonne

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