Understanding the Weight of 100 Milliliters of Water

The weight of 100 milliliters (mL) of water is a fundamental concept in various fields, from scientific research to everyday cooking. This article delves into the calculation of the weight of water based on its density. We will explore why the weight of 100 mL of water is 100 grams (g) using the metric system, and how this can be understood in different contexts.

The Density of Water

The density of water is a constant and convenient measure, with a density of 1 gmL-1. This means that 1 milliliter (mL) of water weighs 1 gram (g). This constant density is a key feature of the metric system and makes it easy to calculate the weight of any volume of water.

Calculation of Weight

To find the weight of 100 mL of water, you can use the following formula:

Weight Volume × Density

Weight 100 mL × 1 g/mL 100 g

This calculation shows that 100 mL of water weighs 100 grams. This is a direct result of the density of water being 1 g/mL, which means that the mass of 100 mL of water is exactly 100 grams.

Historical Context and Practical Implications

It's worth noting that this relationship between volume and weight of water has a historical context. The metric system, particularly the definition of the liter, was based on the weight of water. Specifically, 1000 mL (1 liter) of water was defined to weigh 1 kilogram (kg). Consequently, 100 mL of water would weight 1/10th of a kilogram, or 100 grams.

Let's break it down step by step. Since 1000 mL of water weighs 1 kg, and 1 kg is equivalent to 1000 g, then 100 mL would weigh:

1000 mL 1000 g (1 kg)

100 mL 1000 g / 10 100 g

Temperature and Pressure Considerations

It's important to note that the density of water can vary slightly with temperature and pressure. The denser the water, the more grams it will contain for a given volume. At 4 degrees Celsius (which is its densest temperature), the density of water is 1000 kg/m3 or 1 g/mL. Therefore, the mass of 100 mL of water at this temperature is indeed 100 grams.

At 20 degrees Celsius, the density of water is approximately 0.99802 g/mL. So, the mass of 100 mL of water at this temperature would be 99.802 grams:

100 mL × 0.99802 g/mL 99.802 g

Practical Examples

In daily life, it's common to measure liquids in liters or milliliters. Since 1 liter (L) is equal to 1000 mL, then 0.1 liter is equal to 100 mL. Therefore, 100 mL is equal to 0.1 liter.

Conclusion

The weight of 100 mL of water is 100 grams, a simple and precise calculation based on its density. This metric system makes it easy to measure and understand the weight of water for both scientific and practical applications.