What do density

Will the water overflow when the ice melts? Explain your answer. Mercury is commonly supplied in flasks containing What is the volume in liters of this much mercury? What is the density of a g rock that displaces Suppose you have a coffee mug with a circular cross section and vertical sides uniform radius. What is its inside radius if it holds g of coffee when filled to a depth of 7. Assume coffee has the same density as water.

What is the depth of the tank if it is 0. A trash compactor can reduce the volume of its contents to 0. Neglecting the mass of air expelled, by what factor is the density of the rubbish increased? What is the average density of the full gas can, taking into account the volume occupied by steel as well as by gasoline? What is the density of These values are parts by mass, not volume. Assume that this is a simple mixture having an average density equal to the weighted densities of its constituents.

The nucleus of an atom has a radius about 10 -5 that of the atom and contains nearly all the mass of the entire atom. The average density of your body decreases when you take a deep breath, because the density of air is substantially smaller than the average density of the body before you took the deep breath.

Skip to main content. Fluid Statics. Search for:. Density Learning Objectives By the end of this section, you will be able to: Define density. Calculate the mass of a reservoir from its density. Compare and contrast the densities of various substances. Which weighs more, a ton of feathers or a ton of bricks? For example, gold will always have a density of You probably have an intuitive feeling for density in the materials you use often.

For example, sponges are low in density; they have a low mass per unit volume. You are not surprised when a large sponge is easy to lift. In contrast, iron is dense. If you pick up an iron skillet, you expect it to be heavy. Students, and even teachers, often confuse mass and density. The words heavy and light on their own refer to mass, and not density. A very large sponge may weigh a lot have a high mass , but its density is low because it still weighs very little per unit of volume. For density, you also need to consider the size, or volume, of the object.

A concrete cube will weigh more than a cube of air the same size because it is denser Show credits Hide from Pitsco Lighter-Than-Air Flight Density is not something that is directly measured. Typically if you want to know the density of something you will weigh it and then measure its volume. Another tricky thing about density is that you can't add densities. If I have a rock that is made up of two minerals, one with a density of 2. This is because both the mass and the volume of the two minerals will be added, and so when they are divided to get the density the result will be between the two.

Typical densities for gasses are on the order of thousandths of grams per cubic centimeter. 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. 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. Each substance has its own characteristic density because of the size, mass, and arrangement of its atoms or molecules. Explain to students that volume is a measure of the amount of space an object takes up. It is always in three dimensions. If measured in centimeters, the answer will be in cubic centimeters cm 3.

Note : Students often confuse volume and area. Check their understanding to make sure they know the difference. Area is a measure of the amount of surface. Volume is a measure of the entire object, including the surface and all the space the object takes up. While the animation is playing, you can demonstrate the measuring process with a cube and ruler. Have students measure along with you to confirm the volume of the cubes. Student groups will not need to measure the volume of the cubes.

The volume of each cube is the same, They will need to measure the mass of each of the eight different cubes and calculate their densities.

Students will use their values for density to identify each cube. Note : The densities students calculate may not be exactly the same as the given densities in this chart. However, their calculations will be close enough that they should be able to identify most of the cubes.

Use a piece of masking tape and a permanent marker to mark the eight cubes with the letters A—H. Expected results : Student values for density for each cube will not be exact, but will be close enough that they should be able to identify each of the cubes. You may notice that the approximate densities given for each cube in this lesson are slightly different than those given in the cube set. Most of this difference is probably due to the value for the volume of each cube.

Since it is likely that these are 1-inch cubes, each side should be 2. We rounded to 2. Explain to students that each substance has its own density because of the atoms and molecules it is made from. The metal, plastic, and wood cubes that students measured each have their own unique density. In general, the density of metal, plastic, and wood can be explained by looking at the size and mass of the atoms and how they are arranged.

In general, the density of wood and plastic are similar because they are made of similar atoms arranged in long chains. The difference in density is mostly based on the arrangement and packing of the polymer chains. Also, since wood is from a living thing, its density is affected by the structure of plant cells and other substances that make up wood. Remind students that they looked at cubes that had the same volume but different masses.

Point out that their activity sheet has drawings of two blocks Sample A and Sample B made of different substances that both have the same mass, but different volumes. Hint : The size, mass, and arrangement of molecules affect the density of a substance.

There are several possible answers for why sample B is more dense than sample A. Any one of these explanations alone, or any combination, could be the reason why Sample B is more dense than Sample A. The American Chemical Society is dedicated to improving lives through Chemistry.

Skip Navigation. Lesson 3. Engage Do a demonstration to show that cubes of the same volume but made of different metals have different masses. 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 Procedure Place the copper and aluminum cube on opposite sides of a simple balance.