Key Concepts

Density is a characteristic building of a substance.The thickness of a problem is the relationship between the mass of the substance and also how much space it takes increase (volume).The massive of atoms, your size, and also how they space arranged recognize the density of a substance.Density equates to the massive of the substance separated by the volume; D = m/v.Objects v the very same volume but different mass have various densities.

You are watching: Why is density a characteristic property

Summary

Students will certainly observe a copper and also an aluminum cube of the exact same volume put on a balance. Lock will see that the copper has a better mass. College student will shot to build an explanation, ~ above the molecule level, for just how this deserve to be. Students room then offered cubes of different materials the all have the very same volume. Students identify the thickness of every cube and identify the problem the cube is made from.

Objective

Students will be able to calculate the thickness of different cubes and also use these values to identify the substance each cube is made of. Students will have the ability to explain that the size, mass, and also arrangement the the atoms or molecules of a problem determines that density.

Evaluation

Download the student task sheet, and distribute one per student when specified in the activity. The activity sheet will serve together the “Evaluate” component of every 5-E lesson plan.

Safety

Make certain you and your students wear correctly fitting goggles.

Materials for Each Group

Cubes significant A–H the you will certainly share with other groupsBalance that have the right to measure in gramsCalculator

Materials for the Demonstration

Copper cube and also aluminum cube of the same volumeBalance

Notes about the materials

Cubes

For this lesson, you will require a collection of cubes of various materials that are all the exact same volume. This sets that cubes are available from a range of suppliers. Flinn clinical sells a density Cube Set, Product #AP6058. This collection comes through 10 cubes—4 metal, 3 plastic, and 3 wood. The is simpler for student if you minimize the number come 8 by using all the samples the metal but only two wood and also two plastic cubes. We suggest using the nylon (off-white, the very least dense) plastic cube and the PVC (gray, many dense) plastic cube. Because that the wood, we suggest using the oak (darker and most dense) and also either the jaw or poplar (paler, much less dense). In the activity, each team will should measure the massive of every of the eight cubes. Groups will should measure and also record their data for a cube and also pass it along to one more group until each team has used each the the cubes.

Balances

Use a simple, plastic, two-sided balance the looks favor a see-saw because that the demonstration. Among the least expensive is Delta education Primary Balance (21-inch) Product #WW020-0452. Have actually students use any balance that have the right to measure in grams.

Metric ruler

Students will use a metric leader in the engage part of the activity when they measure the length, width, and also height of a cube together with you.

About this Lesson

This is the first lesson in i beg your pardon students view models of molecules that space more facility than a water molecule. Several of these molecules may look a small intimidating. Let students recognize that they do not must memorize or attract these molecules. Because that the function of this chapter, student only have to think about the size and mass that the atoms that consist of the molecule and how they are arranged in the substance.


Engage

Do a demonstrate to display that cubes that the very same volume however made of various metals have different masses.

Question to investigate

Do cubes of exactly the exact same size and also shape, have the exact same mass?

Materials because that the demonstration

Copper cube and also aluminum cube that the very same volumeBalance

Procedure

Place the copper and also aluminum cube on opposite political parties of a straightforward balance.

*

Expected results

The copper cube will have a higher mass than the aluminum cube.

Lead a discussion about why the copper cube has actually a better mass than the aluminum cube.

Tell students that both cubes are exactly the very same size and also both room solid through no hollow spots. Define that the aluminum cube is make of only aluminum atoms and also the copper cube is make of just copper atoms.

Ask students:

How can two objects, which are specifically the exact same size and shape, have a various mass?Help students understand that the difference in fixed must have something to execute with the atom in every cube. There are three feasible explanations about the copper and aluminum atom in the cubes that might explain the distinction in mass. Copper atoms might have an ext mass than aluminum atoms. Copper atoms can be smaller so more can right in the same volume. Explore

Have students calculate the thickness of eight various cubes and use the characteristic residential or commercial property of thickness to correctly determine them.

Student groups will not need to measure the volume the the cubes. The volume of every cube is the same, 15.6 cm3, and is offered in your chart ~ above the task sheet. Lock will have to measure the mass of each of the eight various cubes and also calculate their densities. Students will use their worths for thickness to recognize each cube.

Note: The densities students calculate might not be specifically the very same as the provided densities in this chart. However, their calculations will be close enough that they should be able to identify most of the cubes.

Question come investigate

Can friend use density to recognize eight cubes do of different materials?

Materials for the class

Set that eight cubes of equal volumeCalculator

Teacher preparation

Use a item of masking tape and a long-term marker to mark the eight cubes v the letters A–H.

Materials because that each group

Cubes significant A–H the you will certainly share with other groupsBalance that can measure in gramsCalculator

Procedure

The volume of every cube is offered in the chart. The is 15.6 cm3.Find the fixed in grams of each cube using a scale or balance. Document this fixed in the chart. Profession cubes with other groups until you have actually measured the fixed of all eight cubes.Calculate the density using the formula D = m/v and also record it in the chart.Table 1. Volume, mass, and density for unknowns A–HSampleVolume (cm3)Mass (g)Density (g/cm3)MaterialABCDEFGH
15.6
15.6
15.6
15.6
15.6
15.6
15.6
15.6
Table 2. Almost right densities for miscellaneous materials.MaterialApproximate density (g/cm3)AluminumBrassCopperSteelPVCNylonOakPine or poplar
2.9
8.8
9.3
8.2
1.3
1.2
0.7–0.9
0.4–0.6
Compare the value you discovered for density with the given value in the chart below to recognize which cube is made the end of i m sorry material. Compose the surname of the product in your chart for cubes A–H.

Expected results: Student worths for thickness for every cube will certainly not be exact, however will it is in close sufficient that lock should have the ability to identify each of the cubes. You may notice that the almost right densities provided for each cube in this lesson room slightly various than those offered in the cube set. Most of this difference is probably due to the worth for the volume of each cube. Because it is most likely that these are 1-inch cubes, each side must be 2.54 cm. We rounded come 2.5 cm due to the fact that students can make this measurement more easily.

Extend

Have students explain on the molecular level why two blocks of various materials that have actually the same mass can have various densities.

Remind students the they looked at cubes that had the exact same volume however different masses. Allude out the their activity sheet has illustrations of two blocks (Sample A and Sample B) do of various substances that both have the same mass, however different volumes.

*

Ask students:

What is the thickness of Sample A?Volume = 5 × 5 × 4 = 100 cm3Mass = 200 gDensity = 200 g/100 cm3 = 2g/cm3What is the thickness of Sample B?Volume = 5 × 5 × 2 = 50 cm3Mass = 200 g density = 200 g/50 cm3 = 4g/ cm3

Give two feasible explanations because that why one sample is more dense than the other.

Hint: The size, mass, and also arrangement of molecules impact the thickness of a substance. There space several feasible answers because that why sample B is much more dense than sample A.

Sample B atoms can have an ext mass 보다 Sample A atoms. Sample B atoms might be smaller than Sample A atom so much more can to the right in the exact same volume. Sample B atoms can be arranged differently so more Sample B atoms than Sample A atom fit in the same size cube.

See more: 4 Reasons Why Does My Dog Rub His Face On The Ground ? Why Does My Dog Rub Itself In The Grass

Any among these explanations alone, or any combination, might be the factor why Sample B is more dense 보다 Sample A.