What is Density? DENSITY is a physical property of matter, as each element and compound has a unique density associated with it. Density defined in a qualitative manner as the measure of the relative "heaviness" of objects with a constant volume. For example: A rock is obviously more dense than a crumpled piece of paper of the same size. A styrofoam cup is less dense than a ceramic cup.

Density may also refer to how closely "packed" or "crowded" the material appears to be - again refer to the styrofoam vs. ceramic cup.

What is the relative density of ice and water?

Density of Ice vs. Water

Title: Density of Unknown Solids Activity 10 Title: Density of Unknown Solids

Read pg. A-41 Challenge: How can you use density to identify solids? Hypothesis/Initial Thoughts:

If you had a 5-g piece of plastic, and were told its density was 1 If you had a 5-g piece of plastic, and were told its density was 1.1 g/cm3, how could you identify the type of plastic it was made from? Turn to table 3 in activity 9 The characteristic density of a material is one piece of information that can lead to the deduction of the identity of a substance Further identification tests would be needed

Substances have characteristic densities (at specific temperatures and pressures). If the density of a substance is known, this evidence can help identify the material of an object.

Materials: 2 unknown solids balance graduated cylinder water source pipette Calculator Forceps Goggles

Safety: Put on goggles and use forceps to work with the metals. This is because we do not know what they are and they might be hazardous.

Procedure: 1. Use a balance to determine the mass of each solid. Record its mass in the data table. 2. Fill the graduated cylinder with 20-mL of water. Place one of the solids gently in the graduated cylinder. Read how much the water level goes up. Record the change in volume in the data table. 3. Repeat for the second solid.

Calculate the density of the two solids Calculate the density of the two solids. To do this divide the mass of each by its measured volume. Record the density in the data table. Record the results of 3 other groups. Find the average density.

Data/Observation: Table 1: Data for Two Metallic Solids Name of Object Mass (g) Volume (cm3 or mL) Density (g/ cm3 or g/mL)

Data/Observation: Table 2: Average Density Name of Object Our Density (g/ cm3 or g/mL) Grp ___ Density (g/ cm3 or g/mL) Avg. Object’s Material

Identify the Unknown Solids Complete Student Sheet 5.1, Chemical Safety Data Sheet.