Density Objective Learn how to calculate density

Density is a way of comparing the mass of an object to its size (volume). If an object feels heavy for its size, it has a high density. A dense object has more material (atoms) packed into a smaller area. Density cannot be measured directly, it must be calculated. The formula used to calculate density is density = mass/volume or D = m/v. The typical label for density is g/mL or g/cm3. Density is a useful tool for scientist. It is often used to help identify a pure substance. A pure substance will have one unique density. For example, each element on the periodic table has a density from any other element. If you had an unknown gas, you could calculate the density of it to identify it. The same is true for minerals- though several minerals may have the same density so other properties would also need to be used to identify the mineral. If you have ever noticed oil floating on water, that is an example of density. Objects that are less dense than water, it will float. Waters density is 1.0g/mL.

1. In general terms, describe what density is.

2. How could density be used to identify an unknown substance?

3. Density must be calculated using a math formula. What is the formula for density?

4. What is a typical label for density?

*Obviously both water and ice are the same substance- so should have the same density. But does it? Then why does ice float? Suggest an explanation.

Part 2- Working with the density formula Using basic algebra, the density formula can be “changed” to solve for mass or volume. However when solving for either mass or volume, I would encourage you to use the original formula and use your algebra skills to solve for the unknown. The other option is to learn the other 2 formulas- not what I would encourage. I would rather see you use the skills you have learned than memorize more “stuff”.

1. What would the formula be for calculating mass if you know the density and volume? Use you algebra to come up with it. What would the normal label for mass be?

2. What would the formula be for calculating volume if you know the density and mass? What would the normal label for volume be?

3. Calculate the density of a metal that has a mass of 27.32g and volume of 6.85cm3.

4. Calculate the mass of a gas that has a density of 0.000048g/cm3 and occupies 60.0cm3.

5. Calculate the volume occupied by a mineral that has a mass of 27.16g and a density of 2.91g/cm3.

http://www.elmhurst.edu/~chm/vchembook/120Adensity.html This website contains information on density.