Mass and Liquid Volume

When we want to know how heavy something is or how much liquid a container can hold, we use specific units of measurement. Let's learn about the metric units for mass and liquid volume!

What is Mass?

Mass tells us how heavy an object is. To measure mass, we use grams (g) and kilograms (kg).

• Gram (g): We use grams to measure very light objects. For example, a single paperclip or a small grape weighs about $1\text{ g}$.
• Kilogram (kg): We use kilograms to measure heavier objects. A heavy dictionary or a small puppy might weigh about $1\text{ kg}$.

The most important rule to remember about mass is how they connect: $1\text{ kg} = 1,000\text{ g}$

What is Liquid Volume?

Liquid volume (sometimes called capacity) tells us how much liquid fits inside a container. We measure this using milliliters (mL) and liters (L).

• Milliliter (mL): We use milliliters for small amounts of liquid. A few drops of water or a spoonful of medicine is measured in mL.
• Liter (L): We use liters for larger amounts of liquid. A big bottle of soda or a pitcher of lemonade is measured in liters.

The rule connecting liters and milliliters is exactly like the rule for mass: $1\text{ L} = 1,000\text{ mL}$

Solving Measurement Problems

Let's look at a few examples to see how we use these measurements in real life.

Example 1: Would you measure a watermelon in grams or kilograms? Answer: A watermelon is quite heavy. Because it is heavy, you would use kilograms to measure its mass.

Example 2: A cup holds about 250 ___. Answer: A standard drinking cup holds a small amount of liquid, much less than a large $1\text{ L}$ bottle. Therefore, it holds about $250\text{ mL}$.

Example 3: Which is heavier: $2\text{ kg}$ or $1,500\text{ g}$? Answer: To compare them, they need to be in the same unit. Let's change kilograms to grams. Since $1\text{ kg} = 1,000\text{ g}$, we multiply by $1,000$: $2\text{ kg} = 2,000\text{ g}$ Now compare $2,000\text{ g}$ and $1,500\text{ g}$. Because $2,000$ is greater than $1,500$, $2\text{ kg}$ is heavier.