# How does the relationship between mass and volume affect density

### Density: A relationship of mass and volume using liquids - Objects with the same mass but different volumes have different densities. - Objects with different How does volume affect density? What happens when two. Mass is a factor in density, the density is proportional to the mass. So as the mass increases, so does the density, provided the volume remains. Objects that have a large mass and small volume have a high density. Learning Objectives: What will students know and be able to do as a result of . What is the relationship between mass and volume for an object that has a low density?.

Factors Affecting Density of Matter by Ron Kurtus revised 5 April The density of an object or quantity of matter is its mass divided by its volume. This is usually measured under standard conditions for temperature and pressure: One factor affecting the density of a material is how concentrated the atoms are in a given volume. In some cases, materials made of atoms with a lower atomic weight have a greater density than those with a higher atomic weight, due to the atoms being more tightly packed. This is especially true for solids. Non-standard conditions can result in a change of volume, affecting the density of the materials. Also, certain temperatures and pressures can result in a change the state of the matter, which also affects the density. Questions you may have include: How does atomic mass affect density? How does density change with temperature and pressure?

How does change of state affect density? This lesson will answer those questions. Units Conversion Concentration of atoms An important factor in determining the density of a material is its mass for a given volume. Although you would think the total mass would only be a function of the material's atomic weight relative atomic massit is not always the case. The atoms in some materials—especially solids—are closely packed compared to those of other materials.

Thus, it is possible for a material made of atoms of a lower atomic number to be heavier than that of a high atomic number for a given volume.

• Factors Affecting Density of Matter
• How does mass affect density? How does volume affect density?
• Density: A relationship of mass and volume using liquids

How does mass affect density? How does volume affect density? What happens when two liquids with different densities are put together? How will the teacher introduce the lesson to the students? Two beakers, labeled A and B, filled with clear colorless liquids.

Students are in groups of 3. Each chooses a number — 1, 2. On the white wipe board, 3's draw a picture of beakers A and B. The teacher places an ice cube in each. What could be different to cause one ice cube to float and one to sink? Students brainstorm answers, without them specifically stating what they think the substances are. Randomly call on students to share the group's suggestions. They should answer that it could be the cubes that are different substances or the liquids are different.

What can we test to see which one is different? You should get the suggestion to switch the cubes. Based on these results, what is different — the liquid or the cubes? Answer — the liquids are different. Which liquid has the greater density — the liquid in beaker A or B? After the group's discuss the answer, 2's label the liquids in the drawings of the beakers - one high density and the other low density.

What substances do you think each of the liquids are? Randomly call on students. Then, tell them what the liquids were and which beakers they were in. Answer — one liquid is plain water and the other is rubbing alcohol.

Some of these molecules may look a little intimidating. Let students know that they do not need to memorize or draw these molecules. For the purpose of this chapter, students only need to think about the size and mass of the atoms that make up the molecule and how they are arranged in the substance.

Engage Do a demonstration to show that cubes of the same volume but made of different metals have different masses.

## What is Density?

Question to investigate Do cubes of exactly the same size and shape, have the same mass? Materials for the demonstration Copper cube and aluminum cube of the same volume Balance Place the copper and aluminum cube on opposite sides of a simple balance. Expected results The copper cube will have a greater mass than the aluminum cube.

Lead a discussion about why the copper cube has a greater mass than the aluminum cube. Tell students that both cubes are exactly the same size and both are solid with no hollow spots. Explain that the aluminum cube is made of only aluminum atoms and the copper cube is made of only copper atoms. How can two objects, which are exactly the same size and shape, have a different mass? Help students understand that the difference in mass must have something to do with the atoms in each cube.

There are three possible explanations about the copper and aluminum atoms in the cubes that could explain the difference in mass. Copper atoms might have more mass than aluminum atoms. Copper atoms might be smaller so more can fit in the same volume. Copper and aluminum atoms might be arranged differently so more copper atoms fit in the same size cube. Explain that any one of these explanations alone, or two or three together, could be the reason why the copper cube has more mass.

Give each student an activity sheet. Students will record their observations and answer questions about the activity on the activity sheet.

Look at the teacher version of the activity sheet to find the questions and answers. Project an illustration and use the pictures of the copper and aluminum atoms to introduce the concept of density.

### Factors Affecting Density of Matter by Ron Kurtus - Physics Lessons: School for Champions

Have students turn to the illustration of copper and aluminum cubes and their atoms on their activity sheet. Show students the image Aluminum and Copper Atoms Point out that the copper atoms are slightly smaller than aluminum atoms.

This smaller size means that more copper atoms can fit in the same amount of space. So, the copper cube contains more atoms than the aluminum cube.

## Density – a relationship of mass and volume

Although they are smaller, individual copper atoms actually have more mass than individual aluminum atoms. The combination of more atoms, each with a greater mass, makes a copper cube weigh more than an aluminum cube of the same size and shape. Explain to students that this idea of how heavy something is compared to the amount of space it takes up is called density. The density of an object is the mass of the object compared to its volume.