Key Concepts

Density is a characteristic property of a substance.The thickness of a problem is the relationship in between the fixed of the substance and also how much an are it takes up (volume).The massive of atoms, their size, and also how they room arranged determine the thickness of a substance.Density amounts to the mass of the substance split by its volume; D = m/v.Objects with the very same volume yet different mass have different densities.

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Summary

Students will certainly observe a copper and an aluminum cube of the very same volume placed on a balance. Castle will watch that the copper has actually a better mass. Student will shot to construct an explanation, top top the molecule level, for how this deserve to be. Students space then given cubes of different materials that all have the very same volume. Students recognize the thickness of every cube and also identify the problem the cube is made from.

Objective

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

Evaluation

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

Safety

Make certain you and your students wear effectively fitting goggles.

Materials for Each Group

Cubes marked A–H the you will certainly share with various other groupsBalance that deserve to measure in gramsCalculator

Materials for the Demonstration

Copper cube and aluminum cube that the very same volumeBalance

Notes about the materials

Cubes

For this lesson, you will need a collection of cubes of various materials that are all the very same volume. These sets of cubes are obtainable from a selection of suppliers. Flinn scientific sells a density Cube Set, Product #AP6058. This set comes v 10 cubes—4 metal, 3 plastic, and 3 wood. That is less complicated for student if you alleviate the number come 8 by making use of all the samples the metal yet only 2 wood and also two plastic cubes. We imply using the nylon (off-white, the very least dense) plastic cube and also the PVC (gray, most dense) plastic cube. For the wood, we imply using the oak (darker and also most dense) and also either the pine tree or poplar (paler, less dense). In the activity, each team will have to measure the mass of each of the eight cubes. Groups will need to measure and also record their data for a cube and also pass it follow me to another group till each team has used each of the cubes.

Balances

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

Metric ruler

Students will use a metric ruler in the engage portion of the task when they measure the length, width, and height of a cube in addition to you.

About this Lesson

This is the first lesson in i beg your pardon students watch models of molecules that room more facility than a water molecule. Few of these molecules might look a little intimidating. Permit students know that they execute not must memorize or draw these molecules. For the function of this chapter, students only should think around the size and also mass the the atoms that make up the molecule and how they room arranged in the substance.


Engage

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

Question come investigate

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

Materials because that the demonstration

Copper cube and aluminum cube that the same volumeBalance

Procedure

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

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Expected results

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

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

Tell students the both cubes are precisely the very same size and also both space solid with no hole spots. Define that the aluminum cube is made of only aluminum atoms and also the copper cube is make of only copper atoms.

Ask students:

How have the right to two objects, i m sorry are precisely the very same size and also shape, have actually a various mass?Help students understand that the distinction in mass must have something to perform with the atom in each cube. There are three possible explanations around the copper and aluminum atom in the cubes that might explain the distinction in mass. Copper atoms could have an ext mass than aluminum atoms. Copper atoms can be smaller sized so an ext can right in the same volume. Explore

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

Student groups will not should measure the volume the the cubes. The volume of every cube is the same, 15.6 cm3, and also is provided in your chart ~ above the activity sheet. Castle will should measure the mass of each of the eight various cubes and also calculate their densities. Student will usage their values for density to recognize each cube.

Note: The densities student calculate may not be specifically the exact same as the provided densities in this chart. However, their calculations will certainly be close enough that castle should be able to identify many of the cubes.

Question to investigate

Can girlfriend use thickness to recognize 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 irreversible marker to mark the eight cubes v the letters A–H.

Materials because that each group

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

Procedure

The volume of each cube is provided in the chart. That is 15.6 cm3.Find the fixed in grams of each cube using a range or balance. Record this fixed in the chart. Trade cubes with other teams until you have actually measured the fixed of all eight cubes.Calculate the density using the formula D = m/v and record the 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 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 provided value in the chart below to recognize which cube is made out of which material. Write the surname of the material in your chart because that cubes A–H.

Expected results: Student values for thickness for every cube will certainly not be exact, but will it is in close sufficient that castle should be able to identify each of the cubes. Girlfriend may an alert that the approximate densities given for every cube in this lesson are slightly different than those given in the cube set. Many of this distinction is probably because of the value for the volume of every cube. Because it is likely that these are 1-inch cubes, each side must be 2.54 cm. Us rounded to 2.5 cm since students can make this measurement more easily.

Extend

Have students describe on the molecular level why 2 blocks of various materials that have the very same mass deserve to have various densities.

Remind students that they looked in ~ cubes that had the very same volume however different masses. Allude out that their task sheet has illustrations of 2 blocks (Sample A and also Sample B) make of different substances that both have actually the same mass, however 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 thickness 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 than the other.

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

Sample B atoms can have more mass than Sample A atoms. Sample B atoms could be smaller sized than Sample A atoms so more can fit in the exact same volume. Sample B atoms could be arranged differently so more Sample B atoms 보다 Sample A atoms fit in the exact same size cube.

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Any among these explanations alone, or any type of combination, could be the reason why Sample B is an ext dense 보다 Sample A.