Learning Objectives
- Understand the concept of weight (heavy and light)
- Compare the weights of different objects
- Learn about kilograms (kg) and grams (g)
- Use a balance to compare weights
- Solve simple problems on weight
Key Concepts
Heavy and Light
Some things are heavy, like a bag full of books, and some things are light, like a feather. We can often tell which is heavier by holding one object in each hand. But to know the exact weight, we need to measure it using a weighing scale or a balance.
Kilograms and Grams
We measure weight in kilograms (kg) and grams (g). A kilogram is used for heavier things like a bag of rice or your body weight. A gram is used for lighter things like a biscuit or a small packet of salt. 1 kilogram = 1000 grams. A packet of chips might weigh about 50 grams, and a watermelon might weigh about 3 kilograms.
Using a Balance
A balance has two pans. You put the object on one pan and known weights on the other pan. When both pans are level (at the same height), the weight of the object equals the total of the known weights. If the object side goes down, the object is heavier.
Everyday Weights
Here are some common weights to remember: A loaf of bread is about 400 g. An apple is about 200 g. A bag of sugar is usually 1 kg or 5 kg. You might weigh about 25 kg to 35 kg. Knowing common weights helps you estimate.
Important Terms
- Weight: How heavy or light an object is
- Kilogram (kg): A unit used to measure heavier things; 1 kg = 1000 g
- Gram (g): A unit used to measure lighter things
- Balance: A tool used to compare and measure weight
- Weighing Scale: A machine that shows the weight of an object
Quick Revision
- 1 kilogram = 1000 grams
- Half a kilogram = 500 grams
- Use kg for heavy things and g for light things
- A balance compares weights by making both sides level
- Common weights: apple ~ 200 g, bread ~ 400 g, sugar packet ~ 1 kg
- Estimate first, then measure to check