### Key Concepts

Just choose solids, liquids additionally have their very own characteristic density.The volume that a liquid can be measured straight with a graduated cylinder.The molecules of different liquids have various size and also mass.The mass and size the the molecules in a liquid and also how carefully they are packed together determine the thickness of the liquid.Just prefer a solid, the density of a liquid amounts to the mass of the liquid separated by the volume; D = m/v.The thickness of water is 1 gram every cubic centimeter.The thickness of a substance is the exact same regardless the the dimension of the sample.

You are watching: What is the density of the unknown liquid?

### Summary

Students measure the volume and also mass that water to recognize its density. Then they measure up the fixed of various volumes that water and also discover that the thickness is constantly the same. Students do a graph of the relationship in between the volume and the massive of water.

### Objective

Students will be able to measure the volume and also mass that water and calculate its density. Students will be able to explain that since any volume that water always has the exact same density, in ~ a given temperature, that density is a characteristic property of water.

### Evaluation

Download the student task sheet, and also distribute one per student when specified in the activity. The task sheet will certainly serve as the “Evaluate” component of each 5-E great plan.

### Safety

Make sure you and your student wear appropriately fitting goggles.

### Materials for Each Group

Graduated cylinder, 100 mlWaterBalance that actions in grams (able to measure up over 100 g)Dropper

### Materials for the Demonstration

WaterTwo identical buckets or big containers
Engage

## Do a demonstrate to present the idea that water has density.

### Materials

WaterTwo identical buckets or big containers

### Teacher preparation

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

### Procedure

Select a student to lift both buckets that water. Explore

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

Tell students that they room going to try to find the density of water.

What 2 things carry out you need to understand in bespeak to uncover the thickness of water?Students should realize that they need both the volume and also mass of a sample the water to uncover its density. How can you measure a volume that water? imply that students use a graduated cylinder to measure up volume in milliliters. Remind students that each milliliter equates to 1 cm3. How deserve to you measure up the mass of water?Suggest that students use a balance to measure the fixed in grams. Tell students the they can find mass by weighing the water. However, since water is a liquid, it needs to it is in in some kind of container. Therefore in bespeak to sweet the water, they need to weigh the container, too. Define to students that they will need to subtract the massive of one empty i graduated cylinder native the massive of the cylinder and also water to obtain the massive of just the water. ## Have students discover the massive of different volumes the water to display that the thickness of water does not rely on the size of the sample.

### Question to investigate

Do different amounts of water have the exact same density?

### Materials for each group

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

### Procedure

Find the massive of an empty graduated cylinder. Document the mass in grams in the graph on the activity sheet.

Pour 100 mL of water into the graduated cylinder. Shot to it is in as accurate as possible by checking the the meniscus is ideal at the 100-mL mark. Use a dropper to include or remove little amounts that water. Weigh the i graduated cylinder v the water in it. Document the fixed in grams. Uncover the fixed of just the water by subtracting the fixed of the empty graduated cylinder. Document the mass of 100 mL of water in the chart. Use the mass and also volume of the water to calculation density. Document the density in g/cm3 in the chart.Pour off water till you have 50 mL that water in the graduated cylinder. If friend accidentally pour the end a little too much, add water until you get as close together you can to 50 mL.

Find the massive of 50 mL the water. Record the fixed in the task sheet. Calculate and also record the density. Next, to water off water until you have 25 mL of water in the graduated cylinder. Discover the mass of 25 mL the water and also record the in the chart. Calculate and also record the density.Table 1. Detect the density of various volumes the water.Volume the water100 mililiters50 mililiters25 mililitersMass of i graduated cylinder + water (g)Mass that empty graduated cylinder (g)Mass that water (g)Density the water (g/cm3)

### Expected results

The density of water must be close to 1 g/cm3. This is true because that 100, 50, or 25 mL.

Look at your values for thickness in her chart. Does the density of the different volumes that water seem to be around the same? aid students view that most of the various values for density are close to 1 g/cm3. They may wonder why your values space not all precisely 1 g/cm3. One reason could be inaccuracies in measuring. Another reason is the the density of water changes with temperature. Water is most thick at 4 °C and also at the temperature has a thickness of 1 g/cm3. In ~ room temperature, about 20–25 °C, the thickness is about 0.99 g/cm3. What is the density of water in g/cm3? students answers will vary, however their values should mostly be about 1 g/cm3.

## Discuss student observations, data, and graphs.

Use her graph to discover the massive of 40 mL that water. What is the density of this volume that water?The massive of 40 mL the water is 40 grams. Because D = m/v and mL = cm3, the thickness of water is 1 g/cm3.Choose a volume in between 1 and also 100 mL. Use your graph to discover the mass. What is the density of this volume that water? whether students sweet 100, 50, 25 mL or any other amount, the density of water will always be 1 g/cm3.

Tell student that density is a characteristic residential or commercial property of a substance. This way that the thickness of a problem is the same regardless the the dimension of the sample. 