Parts of a Computer – Input, Output, and Storage Devices

TOPIC: Measurement of Mass
SUBTOPIC: Meaning, Instruments, Metric Units (g, kg), Practical Weighing
CLASS: Basic 3
AGE: 8–9 years
DATE: __________
PERIOD: __________
DURATION: 40 minutes

LEARNING OBJECTIVES (as per scheme)

By the end of the lesson, pupils should be able to:

1. Mention past methods of obtaining mass (e.g., hand-hefting, comparing with stones on a balance).
2. Explain the meaning of mass.
3. Mention instruments for measuring mass.
4. Identify metric units (g, kg).
5. Measure and record weights/masses of objects.
6. Compare masses of different objects.
7. Analyze reasons for differences in mass readings (zero error, moving pointer, uneven surface).

KEY VOCABULARY

Mass, weight (everyday use), scale, balance, gram (g), kilogram (kg), zeroing, pointer, beam.

INSTRUCTIONAL MATERIALS

Tabletop beam balance, spring/digital scale, sample objects (apple, chalk box, water bottle), 100 g/200 g calibration masses (or labeled packets), chart of unit conversions.

CONTENT OF THE LESSON

Meaning of Mass:
Mass is the amount of matter in an object. We measure it to know how heavy things are.

Past (Non-standard) Methods:
Hefting by hand; comparing two objects on a simple balance using stones/sand as counterweights.

Standard Instruments:

• Beam balance (two pans).
• Spring scale (pointer shows reading).
• Digital scale (numbers displayed).

Metric Units:

• Gram (g): small masses (snacks, fruits).
• Kilogram (kg): heavy items (bags, rice).
  Conversion: 1 kg = 1000 g.

How to Measure Accurately:
Zero the scale first; place object gently; keep on a flat surface; wait for pointer/display to settle; record with units.

Why Readings May Differ:
Scale not zeroed, moving while measuring, reading before pointer settles, using different instruments.

DIAGRAMS/ILLUSTRATIONS

• Labeled beam balance (pans, beam, pointer).
• Digital scale reading in g/kg.

INTRODUCTORY ACTIVITY

Give two objects of similar size (e.g., chalk box and eraser). Ask which is heavier by hand, then verify using the scale.

CLASS EXERCISE 1

Measure the mass of three classroom objects using the scale. Record in g or kg.

CLASS EXERCISE 2

Convert:
(a) 2 kg = ______ g
(b) 750 g = ______ kg
(c) 1.5 kg = ______ g

CLASS EXERCISE 3 (Reasoning)

Two groups get different masses for the same object. List two reasons why.

ASSIGNMENT (MCQs)

1. The instrument that compares two masses directly is a ______.
   a) ruler b) beam balance c) thermometer d) clock
2. 1 kilogram equals ______ grams.
   a) 10 b) 100 c) 1000 d) 10,000
3. A digital scale shows 250. The unit is most likely ______.
   a) cm b) g c) L d) m
4. Before measuring mass, we should first ______ the scale.
   a) warm b) zero c) shake d) paint
5. Which is likely heavier?
   a) pencil (10 g) b) textbook (0.5 kg) c) paper clip (1 g) d) seed (0.2 g)