Hello, everyone! Welcome to our Basic Science class for Primary 3. In the previous lesson, we learned about the measurement of length. Today, we will be learning about the measurement of mass.

### Lesson Objectives

By the end of this lesson, you will be able to:

- Explain the meaning of Mass & Weight
- Identify and mention various instruments for measuring mass & Weight
- Identify the metric units of measuring mass
- Use mass balance to estimate the masses of objects in the classroom such as pencils, notebooks

Let’s begin our exciting lesson to understand how to measure mass!

### What is Mass and Weight?

Mass is the amount of matter in an object. It’s a measure of how much “stuff” an object contains. Weight, on the other hand, is the force of gravity acting on an object’s mass.

Imagine you have a big, heavy rock and a small, light feather. The rock has more mass than the feather, meaning it contains more matter. However, the weight of the rock will be greater than the feather because gravity pulls on it more strongly due to its larger mass.

### Instruments for Measuring Mass and Weight

There are several instruments we use to measure mass and weight:

**Mass Balance**: This is used to measure the mass of objects. It works by comparing the object’s mass to known standard masses.**Spring Balance**: This measures the weight of objects. It uses a spring that stretches or compresses based on the force of gravity acting on the object.**Digital Scale**: This is an electronic device used for precise mass measurements. It uses sensors to detect the object’s mass and displays the reading digitally.**Beam Balance**: This measures mass by comparing an unknown mass with a known mass. It has a beam that balances when the masses on both sides are equal.**Triple Beam Balance**: This is a type of beam balance with three beams to measure mass more accurately. Each beam has a set of weights that can be moved to balance the object’s mass.**Kitchen Scale:**A kitchen scale is a small, compact scale designed for measuring food items. It often has a digital display and can measure in grams or ounces.

### Metric Units of Mass and Weight

Below is a chart to help you understand the metric units of mass and how to convert from one unit to another:

Symbol | Unit | Equivalent |
---|---|---|

mg | Milligram | 1 mg |

dg | Decigram | 10 mg |

cg | Centigram | 10 dg |

g | Gram | 10 cg |

kg | Kilogram | 1000 g |

t | Tonne | 1000 kg |

### Estimating Masses of Classroom Objects

Now, let’s use a mass balance to estimate the masses of some objects in our classroom. For example, you can estimate the mass of a pencil, a notebook, or any other small item you have.

- Place the object on the mass balance.
- Read the measurement on the scale.
- Record the mass in grams or kilograms.

### Sources

- Measuring Mass – Measuring Instruments
- Explainer: How do mass and weight differ?
- Weight – Students | Britannica Kids

### Quiz & Evaluation

Let’s see how much you’ve learned, complete this quiz to test your knowledge.

Question 1: What is the unit for measuring mass that is abbreviated as “g”?