Measurement - Measurement of Weight using Metric Units

Understanding Mass and Weight: Weight (or mass) tells us how heavy an object is. In Grade 3, we use weighing balances and digital scales to measure weight. Imagine a balance scale with two pans: if one pan is lower than the other, the object in that pan is heavier. If the pans are level, the weights are equal.

The Unit 'Gram' ($g$): The gram is the standard metric unit used to measure the weight of light objects. For example, a single paperclip weighs about $1\ g$, and a pencil weighs about $5\ g$. Think of a few drops of water in your palm to visualize the weight of $1\ g$.

The Unit 'Kilogram' ($kg$): The kilogram is the standard metric unit used to measure the weight of heavy objects. For example, a large textbook or a liter of water weighs approximately $1\ kg$. Visualize holding a large bag of sugar to understand how $1\ kg$ feels.

Conversion Rule: There is a fixed relationship between the two units: $1000$ grams make up $1$ kilogram. This is written as $1\ kg = 1000\ g$. This means a kilogram is $1000$ times heavier than a gram.

Converting $kg$ to $g$: To change kilograms into grams, we multiply the number of kilograms by $1000$. For example, $4\ kg$ becomes $4 \times 1000 = 4000\ g$. A quick way to visualize this is adding three zeros to the end of the kilogram value.

Converting Mixed Units: When we have both kilograms and grams (like $2\ kg\ 500\ g$), we convert the kilogram part to grams first and then add the remaining grams. For example, $2\ kg\ 500\ g = 2000\ g + 500\ g = 2500\ g$.

Standard Weights: In shops, you might see metal weights used on balance scales. These typically come in denominations like $50\ g, 100\ g, 200\ g, 500\ g, 1\ kg, 2\ kg,$ and $5\ kg$. To weigh an object of $750\ g$, a shopkeeper might use a $500\ g$ weight and a $200\ g$ weight and a $50\ g$ weight together.

Comparison of Weights: To compare two weights, they should be in the same unit. Since $1\ kg = 1000\ g$, a $900\ g$ box is lighter than a $1\ kg$ box, even though $900$ is a larger number than $1$.