Mass: Comparing, adding and subtracting

In a nutshell

Mass is how you describe how heavy an object is. You can compare the weights of objects using mass and you can use a weighing scale or balance to find and compare masses of objects.

Comparing mass

Heavier objects have greater mass, so a $500g$ pot is heavier than a $100g$ fork. Remember that you can only compare masses if they have the same unit; a $150g$ book is not heavier than a $5kg$ chair! Use this equation to convert between units:

$1000g = 1kg$

Adding and subtracting mass

Procedure

1.	Make sure the units are the same.
2.	Identify what the question is asking you: "Find the combined mass of ..." means summing the masses. "How much heavier is ..." means subtracting one mass from the other.
3.	Convert the answer back into appropriate units (if required).

Examples

How much heavier is a $2.3kg$ paperweight compared to a $750g$ bottle of water?

$2.3kg = 2300g$

$2300 - 750 =\underline{1550g}$

What is the combined weight of the paperweight and the bottle of water?

$2.3kg = 2300g$

$2300 + 750 = \underline{3050g}$