How Heavy How Light - Units of Weight (Grams and Kilograms)

Understanding Weight: Weight measures how heavy an object is. In our daily lives, we use different units to measure weight based on the size of the object. We use grams ($g$) for light objects and kilograms ($kg$) for heavy ones. Visualise a single toffee or a paperclip; these are measured in grams. Visualise a large watermelon or your own body; these are measured in kilograms.

The Gram ($g$): The gram is a small unit of weight. If you hold a single dry bean or a small button, you are feeling a weight of approximately $1\text{ g}$. Grams are used for things like spices, jewellery, and small stationery items.

The Kilogram ($kg$): The kilogram is the standard unit for heavier items. Imagine a $1\text{ litre}$ bottle of water; it weighs about $1\text{ kg}$. We buy vegetables like potatoes or staples like rice in kilograms.

The Relationship Between Units: The most important rule to remember is that $1000$ grams make up $1$ kilogram ($1\text{ kg} = 1000\text{ g}$). If you have a balance scale with a $1\text{ kg}$ weight on one side, you would need $1000$ tiny $1\text{ g}$ weights on the other side to keep it perfectly level.

Using a Balance Scale: A balance scale or beam balance is used to compare weights. It consists of two pans hanging from a central bar. Visualise the scale: if the left pan is lower than the right pan, it means the object on the left is 'heavier'. If both pans are at the exact same height, the weights are 'equal'.

Standard Weights: To measure accurately, we use fixed weights made of metal. These usually come in denominations such as $50\text{ g}, 100\text{ g}, 200\text{ g}, 500\text{ g}, 1\text{ kg}, 2\text{ kg}, 5\text{ kg},$ and $10\text{ kg}$. Shops often use these on manual scales to weigh flour or sugar.

Converting Units: To change kilograms into grams, we multiply by $1000$ because $1\text{ kg}$ is a larger unit. To change grams into kilograms, we divide by $1000$. For example, half a kilogram is represented as $\frac{1}{2}\text{ kg}$, which is exactly $500\text{ g}$ because $1000 \div 2 = 500$.