Here's why:
* Density is the key: The relationship between volume and mass is governed by density. Density is the mass per unit volume of a substance.
* Different densities: Different substances have different densities. For example, water has a density of 1 gram per milliliter, while iron has a density of 7.87 grams per milliliter.
* Example: If you have 20 ml of water, its mass will be 20 grams because the density of water is 1 g/ml. But if you have 20 ml of iron, its mass will be significantly higher (around 157 grams) because iron is denser than water.
To calculate the mass of a substance, you need to know both its volume and its density using the following formula:
Mass = Volume x Density
