### Key Concepts

Just like solids, liquids additionally have their own characteristic thickness.The volume of a liquid can be measured straight with a graduated cylinder.The molecules of various liquids have actually various size and also mass.The mass and size of the molecules in a liquid and exactly how closely they are packed together determine the thickness of the liquid.Just like a solid, the thickness of a liquid amounts to the mass of the liquid split by its volume; D = m/v.The density of water is 1 gram per cubic centimeter.The density of a substance is the exact same regardless of the size of the sample.

You are watching: How to find the density of an unknown liquid

### Summary

Students measure the volume and also mass of water to determine its density. Then they meacertain the mass of various quantities of water and also discover that the density is always the same. Students make a graph of the partnership between the volume and the mass of water.

### Objective

Students will certainly be able to measure the volume and mass of water and calculate its thickness. Students will certainly be able to describe that since any volume of water constantly has actually the very same thickness, at a given temperature, that density is a characteristic residential or commercial property of water.

### Evaluation

Downpack the student activity sheet, and also distribute one per student once mentioned in the task. The activity sheet will serve as the “Evaluate” component of each 5-E leskid arrangement.

### Safety

Make certain you and your students wear properly fitting goggles.

### Materials for Each Group

Graduated cylinder, 100 mlWaterBalance that steps in grams (able to meacertain over 100 g)Dropper

### Materials for the Demonstration

WaterTwo similar buckets or huge containers
Engage

## Do a demonstration to introduce the principle that water has actually thickness.

### Materials

WaterTwo identical buckets or big containers

### Teacher preparation

Half-fill one bucket and also include only around 1 cup of water to the other.

### Procedure

Select a student to lift both buckets of water. Explore

## Discuss through students just how to discover the volume and also mass of water.

Tell students that they are going to attempt to find the thickness of water.

What 2 points carry out you must know in order to find the density of water?Students need to realize that they require both the volume and mass of a sample of water to uncover its thickness. How have the right to you measure a volume of water? Suggest that students use a graduated cylinder to meacertain volume in milliliters. Remind students that each milliliter equates to 1 cm3.
How deserve to you measure the mass of water?Suggest that students use a balance to measure the mass in grams. Tell students that they can discover mass by weighing the water. However before, considering that water is a liquid, it requirements to be in some kind of container. So in order to weigh the water, they have to weigh the container, too. Exsimple to students that they will need to subtract the mass of an empty graduated cylinder from the mass of the cylinder and water to acquire the mass of just the water.

## Have students find the mass of various volumes of water to show that the thickness of water does not depfinish on the size of the sample.

### Inquiry to investigate

Do various amounts of water have actually the exact same density?

### Materials for each group

Graduated cylinder, 100 mLWaterBalance that steps in grams (able to measure over 100 g)Dropper

### Procedure

Find the mass of an empty graduated cylinder. Record the mass in grams in the chart on the activity sheet.

Pour 100 mL of water right into the graduated cylinder. Try to be as precise as possible by checking that the meniscus is right at the 100-mL note. Use a dropper to add or rerelocate small quantities of water.

Weigh the graduated cylinder via the water in it. Record the mass in grams. Find the mass of only the water by subtracting the mass of the empty graduated cylinder. Record the mass of 100 mL of water in the chart. Use the mass and volume of the water to calculate density. Record the thickness in g/cm3 in the chart.Pour off water until you have 50 mL of water in the graduated cylinder. If you accidentally pour out a little also a lot, include water till you obtain as close as you have the right to to 50 mL.

Find the mass of 50 mL of water. Record the mass in the activity sheet. Calculate and record the density.

Next off, pour off water till you have actually 25 mL of water in the graduated cylinder. Find the mass of 25 mL of water and also record it in the chart. Calculate and record the thickness.Table 1. Finding the density of different volumes of water.Volume of water100 mililiters50 mililiters25 mililitersMass of graduated cylinder + water (g)Mass of empty graduated cylinder (g)Mass of water (g)Density of water (g/cm3)

### Expected results

The thickness of water need to be close to 1 g/cm3. This is true for 100, 50, or 25 mL.

Look at your values for thickness in your chart. Does the density of the different volumes of water seem to be about the same? Help students see that a lot of of the different worths for thickness are close to 1 g/cm3. They may wonder why their values are not all precisely 1 g/cm3. One reason might be inaccuracies in measuring. Anvarious other factor is that the thickness of water alters with temperature. Water is a lot of dense at 4 °C and at that temperature has actually a density of 1 g/cm3. At room temperature, roughly 20–25 °C, the density is about 0.99 g/cm3. What is the thickness of water in g/cm3? Students answers will certainly vary, yet their worths need to mostly be about 1 g/cm3.

## Discuss student observations, information, and also graphs.

Use your graph to find the mass of 40 mL of water. What is the density of this volume of water?The mass of 40 mL of water is 40 grams. Due to the fact that D = m/v and also mL = cm3, the density of water is 1 g/cm3.Choose a volume between 1 and 100 mL. Use your graph to find the mass. What is the thickness of this volume of water? Whether students weigh 100, 50, 25 mL or any various other amount, the thickness of water will certainly always be 1 g/cm3.

Tell students that density is a characteristic residential or commercial property of a substance. This indicates that the thickness of a substance is the same regardmuch less of the size of the sample.