Key Concepts

Density is a characteristic home of a substance.The thickness of a problem is the relationship between the massive of the substance and how much space it takes up (volume).The massive of atoms, their size, and also how they are arranged determine the density of a substance.Density amounts to the fixed of the substance split by its volume; D = m/v.Objects v the exact same volume but different mass have various densities.

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Summary

Students will certainly observe a copper and an aluminum cube that the same volume placed on a balance. Castle will see that the copper has actually a greater mass. Students will try to construct an explanation, ~ above the molecular level, for exactly how this have the right to be. Students are then offered cubes of various materials the all have the same volume. Students determine the density of each cube and identify the problem the cube is do from.

Objective

Students will have the ability to calculate the thickness of different cubes and use these values to recognize the substance every cube is do of. Student will be able to explain the the size, mass, and arrangement the the atom or molecule of a problem determines its density.

Evaluation

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

Safety

Make certain you and also your student wear properly fitting goggles.

Materials because that Each Group

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

Materials for the Demonstration

Copper cube and aluminum cube of the exact same volumeBalance

Notes about the materials

Cubes

For this lesson, friend will need a set of cubes of various materials that are all the very same volume. These sets that cubes are obtainable from a selection of suppliers. Flinn clinical sells a density Cube Set, Product #AP6058. This set comes through 10 cubes—4 metal, 3 plastic, and 3 wood. It is easier for students if you alleviate the number come 8 by utilizing all the samples of metal however only 2 wood and two plastic cubes. We indicate using the nylon (off-white, least dense) plastic cube and the PVC (gray, many dense) plastic cube. For 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 must measure the massive of every of the eight cubes. Teams will should measure and also record your data for a cube and pass it along to one more group till each team has offered each the the cubes.

Balances

Use a simple, plastic, two-sided balance that looks favor 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 have the right to measure in grams.

Metric ruler

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

About this Lesson

This is the first lesson in which students check out models of molecules that room more complex than a water molecule. Few of these molecules may look a tiny intimidating. Allow students know that they perform not need to memorize or attract these molecules. For the function of this chapter, student only need to think about the size and mass that the atoms that make up the molecule and how they space arranged in the substance.


Engage

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

Question come investigate

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

Materials for 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 an easy 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 greater mass 보다 the aluminum cube.

Tell students that both cubes are specifically the very same size and both are solid with no hollow spots. Describe that the aluminum cube is make of just aluminum atoms and the copper cube is made of just copper atoms.

Ask students:

How have the right to two objects, which are precisely the same size and also shape, have a various mass?Help students understand that the difference in fixed must have actually something to execute with the atom in every cube. There space three possible explanations about the copper and also aluminum atoms in the cubes that could explain the distinction in mass. Copper atoms could have much more mass 보다 aluminum atoms. Copper atoms can be smaller sized so an ext can to the right in the same volume. Explore

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

Student groups will not need to measure the volume the the cubes. The volume of each cube is the same, 15.6 cm3, and is provided in your chart on the activity sheet. Castle will need to measure the massive of each of the eight different cubes and calculate their densities. College student will use their values for thickness to identify each cube.

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

Question to investigate

Can you use density to identify eight cubes make of various materials?

Materials because that the class

Set of eight cubes of equal volumeCalculator

Teacher preparation

Use a item of masking tape and a long-term marker to note the eight cubes with the letter A–H.

Materials because that each group

Cubes marked A–H that you will share with various 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 fixed in grams of every cube making use of a range or balance. Document this mass in the chart. Profession cubes through other teams until you have measured the massive of every eight cubes.Calculate the thickness using the formula D = m/v and also 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. Approximate 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 worth you uncovered for density with the offered value in the chart listed below to identify which cube is made the end of which material. Write the name of the product in your chart for cubes A–H.

Expected results: Student values for thickness for each cube will certainly not be exact, however will it is in close enough that castle should be able to identify every of the cubes. Girlfriend may an alert that the almost right densities provided for each cube in this lesson space slightly different than those provided in the cube set. Many of this distinction is probably as result of the value for the volume of every cube. Due to the fact that it is most likely that these are 1-inch cubes, each side have to be 2.54 cm. We rounded to 2.5 cm due to the fact that students deserve to make this measurement more easily.

Extend

Have students define on the molecular level why 2 blocks of different materials that have actually the very same mass can have different densities.

Remind students that they looked in ~ cubes that had the exact same volume but different masses. Point out that their activity sheet has illustrations of 2 blocks (Sample A and Sample B) made of various substances that both have actually the very same mass, however different volumes.

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Ask students:

What is the density 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 보다 the other.

Hint: The size, mass, and arrangement that molecules impact the thickness of a substance. There are several feasible answers for why sample B is an ext dense than sample A.

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

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