7A9 Mass and Density

Vocabulary

• Mass:– How much matter is in an object

• Density:– Physical property of a substance– Mass of a substance per unit of Volume– Mass / Volume, in g / mL or g / cm3

• Quantitative: describe with numbers• Qualitative: describe with words

Background

• Measure Mass AND Volume of a substance.• Calculate Density by dividing mass by volume.• Pure substances have characteristic densities.• So you can use the calculated density to

identify the type of material it is made from.

Data Table: Mass, Volume, Density• Turn lab book sideways and make 5 columns: 3

narrow, 1 wide, and 1 narrow• Object: (Light gray cylinder, Dark gray cylinder,

Light gray bar, Dark gray bar, Light gray cube, and Dark gray cube)

• Mass (g): from balance• Volume cm3: Cylinder=6,

Bar=7.9, Cube=15.6• Density Calculation: M/V• Density (g/cm3)

Procedure 1• Same 6 Objects: 2 cubes, 2 cylinders, 2 bars• Use a Balance to find mass to nearest 0.1gram• Enter the Volumes from the 7A8 Volume Lab• Calculate Densities; divide Mass by Volume• Compare results with table partners. Repeat

any measurements you are unsure of.

New Data Table: Density Identity• Make a new data table with 4 columns.• Object: (Light gray bar, Dark gray bar, Light gray

cube, Dark gray cube, Light gray cylinder, and Dark gray cylinder)

• Density calculated: copy from first data table• Closest Density from Table 3: see page A40• Type of Solid from Table 3:

see page A40

Table 3: Solid Material Densities

PLASTICSHigh-density polyethylene (HDPE)----------Polystyrene (PS)---------------------------------Polyvinylchloride (PVC)------------------------METALSMagnesium---------------------------------------Beryllium------------------------------------------Aluminum-----------------------------------------Titanium-------------------------------------------Zinc-------------------------------------------------Iron-------------------------------------------------Tungsten------------------------------------------

DENSITY (g / cm3)0.951.11.3

1.71.92.74.57.17.919.4

7A9 Mass/Density Analysis pA40

On separate paper, answer each in 1 paragraph.2) Now that you have identified each solid, look at their hazards in Table 2 on page A31. Explain the precautions you must take for each of them.3) A block of wood is 4cm wide, 5cm long, and 10cm high. It weighs 100g. (a) Find its volume (b) Calculate its density (c) Will it sink or float (water is 1g/cm3), (d) If you cut the block in half, calculate the new mass, volume, and density of each piece (e) How do new densities compare to the original?