Weight, mass and volume

Weight and Mass

Distinguishing between Mass and Weight

We often use the terms mass and weight to refer to the same thing. Eg. A grocery store states that a hamburger patty weighs 200g. In science, mass and weight have different meanings and different units of measurement.

MASS – the quantity of matter found in an object. Mass can be measured using a balance or a scale. Common units include grams and kilograms. The mass of an object remains the same everywhere/anywhere in the universe.

WEIGHT – is the force of EARTH’s gravity acting on an object. It is measured in Newtons (N). The Newton is named after Sir Isaac Newton, who lived from 1642 – 1727. A spring scale can be used to measure weight, and often, mass, as well. Weight is the measure of a force, so it has a magnitude and a direction. A mass of 1 kg has a weight of almost 10N downward (toward EARTH). The weight of an object can change depending on its location. For example, an astronaut with a weight of 900N downward on EARTH, weighs only 1/6 as much on the moon (150 N). This is because the moon has a much smaller force of gravity than EARTH.

Volume Volume is a measure of how much space an object occupies; to

determine the volume of a ‘regular’ solid, you can multiply it’s three dimensions together:

volume = length x width x height

This gives measurement in cubic units; gases are often measured in cubic metres (m^3)

To measure liquid volume, the basic unit of measurement is the L; a container measuring 10cm x 10 cm x 10 cm holds 1000cm cubed or 1 L

Since a litre is also equal to 1000mL, 1 cm cubed = 1 mL

mL are used to measure small volumes of fluids

Volume of irregularly shaped objects

How can you measure the volume of an object that does not have a regular shape? You may have noticed that whenever you take a bath, the water rises

as you settle into the tub. You essentially displace the water from where it sits, forcing it to take up other parts of its container.

You can measure irregularly shaped objects by determining the volume of displaced fluids – “finding volume by displacement”

Practise

Volume of larger objects

When objects are too big to fit into a graduated cylinder, volume displacement can be measured using something called an overflow can

Practise