Matter

Chapter Twelve: The Physical Properties of Matter 12.1 Density 12.2 Buoyancy 12.3 Properties of Materials

Investigation 12A How does density determine if an object floats or sinks? Density

12.1 Density Density describes how much mass is in a given volume of a material.

12.1 Density Solids, liquids and gases are matter, so they all have density.

12.1 Volume Volume is the amount of space an object takes up. The volume of a rectangular solid is found by multiplying length times width times height.

12.1 Volume Measuring the volume of liquids is easy. Pour the liquid into a marked container called a graduated cylinder and read the volume.

12.1 Displacement You can find the volume of an irregular shape using a technique called displacement. Find the volume of an irregularly shaped object by putting it in water and measuring the amount of water displaced.

12.1 Density The units used for density depend on whether the substance is solid or liquid. –For liquids use units of grams per milliliter (g/mL) –For solids use density in units of g/cm 3 or kg/m 3.

12.1 Density of common materials Density is a property of material independent of quantity or shape.

12.1 Density of common materials Liquids tend to be less dense than solids of the same material. Water is an exception to this rule. The density of solid water, or ice, is less than the density of liquid water.

12.1 Determining Density To find the density of a material, you need to know the mass and volume of a solid sample of the material. 1.Mass is measured with a balance or scale. 2.Use the displacement method or calculate the volume.

12.1 Determining Density When calculating volume, all of the units of length involved in the calculation must be the same.

12.1 Why density varies Density changes for different substances because: 1.Atoms have different masses. 2.Atoms may be “packed” tightly or loosely.