# Pipetting and Accuracy in Measurement

## What was the mass of the water you pipetted? The volume? Explain why the density of water is 0.998 g/ml and not 1.0 g/ml

## Pipetting and Accuracy in Measurement:

When pipetting, accuracy in measurement is critical to obtaining reliable results. Hence the density of water is 0.998 g/ml and not 1.0 g/ml. The most common sources of error are the users, pipette, and environmental variables, such as humidity and temperature. Measurements can be made in volumes ranging from a few microliters to several milliliters, and they must be precise and accurate.

### The mass of water that was pipetted:

To answer this question, additional information is required. Without the information on how much water was pipetted, it is impossible to determine its mass.

### Volume:

The pipetted volume of water must also be determined to determine its mass. The volume pipetted should be indicated on the pipette.

### Explain why the density of water is 0.998 g/ml and not 1.0 g/ml:

The density of water varies with temperature. The density of water at 4°C is 1.0 g/ml. As temperature rises, water expands, and its density decreases. At 20°C, the density of water is 0.998 g/ml. As the temperature of water rises above 4°C, it becomes less dense, but as the temperature decreases below 4°C, water becomes more dense. Hence the density of water is 0.998 g/ml and not 1.0 g/ml.

## More than 100 words

**Inaccuracies in measurement can lead to inaccurate results**. As a result, when pipetting, accuracy in measurement is critical to obtaining reliable results. The most common sources of error are the users, pipette, and environmental variables, such as humidity and temperature. Measurement can be done in volumes ranging from a few microliters to several milliliters, and it must be precise and accurate. When pipetting, ensure that the pipette is correctly calibrated and that the user's technique is correct. Temperature and humidity should be kept constant, and the lab's guidelines must be followed when pipetting. The mass of water that was pipetted can be calculated by multiplying its volume by its density. To calculate the mass, the pipetted volume of water must also be determined, and the volume pipetted should be indicated on the pipette. The density of water varies with temperature. The density of water at 4°C is 1.0 g/ml. As temperature rises, water expands, and its density decreases. At 20°C, the density of water is 0.998 g/ml. As the temperature of water rises above 4°C, it becomes less dense, but as the temperature decreases below 4°C, water becomes more dense. Hence the density of water is 0.998 g/ml and not 1.0 g/ml.