Key Concepts

Density is a characteristic home of a substance.The thickness of a problem is the relationship in between the massive of the substance and also how much space it takes increase (volume).The massive of atoms, their size, and how they are arranged recognize the density of a substance.Density equals the mass of the substance divided by that volume; D = m/v.Objects with the very same volume yet different massive have various densities.

You are watching: Which has the greater mass?

Summary

Students will observe a copper and an aluminum cube of the exact same volume put on a balance. Lock will watch that the copper has actually a higher mass. Students will shot to develop an explanation, ~ above the molecular level, for how this deserve to be. Students are then offered cubes of various materials the all have the exact same volume. Students recognize the density of every cube and also identify the problem the cube is made from.

Objective

Students will have the ability to calculate the thickness of various cubes and also use these worths to identify the substance every cube is made of. College student will have the ability to explain the the size, mass, and arrangement of the atom or molecules of a substance determines its density.

Evaluation

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

Safety

Make certain you and your students wear appropriately fitting goggles.

Materials for Each Group

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

Materials because that the Demonstration

Copper cube and aluminum cube that the exact same volumeBalance

Notes around the materials

Cubes

For this lesson, girlfriend will require a collection of cubes of various materials that space all the exact same volume. These sets of cubes are easily accessible from a selection of suppliers. Flinn scientific sells a thickness Cube Set, Product #AP6058. This set comes v 10 cubes—4 metal, 3 plastic, and 3 wood. The is less complicated for college student if you mitigate the number to 8 by utilizing all the samples of metal but only two wood and also two plastic cubes. We imply using the nylon (off-white, the very least dense) plastic cube and the PVC (gray, most dense) plastic cube. Because that the wood, we indicate using the oak (darker and also most dense) and also either the pine or poplar (paler, less dense). In the activity, each group will should measure the massive of every of the eight cubes. Groups will should measure and record their data for a cube and also pass it along to an additional group until each group has provided each the the cubes.

Balances

Use a simple, plastic, two-sided balance the looks prefer a see-saw for the demonstration. One of the the very least expensive is Delta education and learning Primary Balance (21-inch) Product #WW020-0452. Have students use any type of balance that can measure in grams.

Metric ruler

Students will usage a metric ruler in the engage portion of the activity when they measure up the length, width, and height the a cube along with you.

About this Lesson

This is the first lesson in i beg your pardon students check out models of molecule that room more complex than a water molecule. Several of these molecules might look a small intimidating. Allow students recognize that they do not must memorize or attract these molecules. Because that the objective of this chapter, students only have to think around the size and mass the the atoms that make up the molecule and also how they are arranged in the substance.


Engage

Do a demonstration to display that cubes the the exact same volume but made of various metals have various masses.

Question come investigate

Do cubes of specifically the very same size and also shape, have the very same mass?

Materials for the demonstration

Copper cube and also aluminum cube of the same volumeBalance

Procedure

Place the copper and aluminum cube ~ above opposite sides of a basic balance.

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Expected results

The copper cube will have actually a better mass 보다 the aluminum cube.

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

Tell students the both cubes are exactly the very same size and both room solid through no hole spots. Explain that the aluminum cube is do of just aluminum atoms and also the copper cube is made of only copper atoms.

Ask students:

How deserve to two objects, i beg your pardon are exactly the same size and also shape, have a various mass?Help students recognize that the difference in mass must have actually something to execute with the atom in every cube. There room three feasible explanations around the copper and aluminum atom in the cubes that might explain the difference in mass. Copper atoms can have more mass than aluminum atoms. Copper atoms can be smaller so more can to the right in the same volume. Explore

Have students calculate the thickness of eight different cubes and also use the characteristic residential property of density to correctly recognize them.

Student teams will not should measure the volume of the cubes. The volume of every cube is the same, 15.6 cm3, and also is given in their chart ~ above the activity sheet. They will should measure the fixed of each of the eight different cubes and also calculate their densities. College student will usage their values for density to determine each cube.

Note: The densities college student calculate may not be specifically the exact same as the given densities in this chart. However, their calculations will be close sufficient that castle should have the ability to identify many of the cubes.

Question to investigate

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

Materials because that the class

Set of eight cubes of equal volumeCalculator

Teacher preparation

Use a item of masking tape and a irreversible marker to note the eight cubes with the letters A–H.

Materials for each group

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

Procedure

The volume of each cube is provided in the chart. It is 15.6 cm3.Find the massive in grams of each cube utilizing a range or balance. Record this mass in the chart. Profession cubes through other teams until you have actually measured the fixed of all eight cubes.Calculate the thickness using the formula D = m/v and record that in the chart.Table 1. Volume, mass, and also 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 assorted materials.MaterialApproximate thickness (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 uncovered for thickness with the given value in the chart below to recognize which cube is made out of i beg your pardon material. Create the name of the material in your chart because that cubes A–H.

Expected results: Student values for thickness for each cube will not it is in exact, but will it is in close sufficient that castle should be able to identify every of the cubes. Girlfriend may an alert that the almost right densities given for every cube in this lesson room slightly various than those offered in the cube set. Most of this difference is probably because of the value for the volume of each cube. Due to the fact that it is most likely that these room 1-inch cubes, each side have to be 2.54 cm. Us rounded to 2.5 cm because students can make this measurement an ext easily.

Extend

Have students define on the molecule level why two blocks of various materials that have actually the very same mass deserve to have various densities.

Remind students that they looked at cubes that had actually the same volume however different masses. Suggest out the their activity sheet has drawings of 2 blocks (Sample A and also Sample B) do of various substances the both have actually the very same mass, yet different volumes.

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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 density of Sample B?Volume = 5 × 5 × 2 = 50 cm3Mass = 200 g density = 200 g/50 cm3 = 4g/ cm3

Give two possible explanations because that why one sample is an ext dense 보다 the other.

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

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

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