# TOPIC: Lab Skills AIM: How do we determine density?

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TOPIC: Lab Skills AIM: How do we determine density?
DO NOW: Explain how layers exist in cappuccino. Layers exist in cappuccino because ________________________________________________________________________________

Density The measure of the amount of mass that is in each unit of volume mass per unit volume

Instruments needed To measure density
Triple beam balance for mass Graduated cylinder for volume of a liquid Metric ruler for volume of a solid

Units used for density or Grams/ml or Grams/cm3

Box A has a greater density than Box B
Because Box A has a greater mass (more matter/ molecules) in the same volume

Warm air rises b/c it is less dense than cold air which sinks.

Density of water 1 gm/mL

Why will an object float or sink? FLOATS when the density of the object is LESS than the density of the liquid.

SINKS when the density of the object is GREATER than the density of the liquid.
Less dense than water More dense than water

Which is more dense? Salt water

Warm water rises b/c it is less dense than cold water which sinks.

Each pure substance has it’s “own density” no matter what size it is.
Facts Each pure substance has it’s “own density” no matter what size it is.

Cut the substance in half each half would still have the same density
So……If I Cut the substance in half each half would still have the same density cut it in half

Cut the block in half M = 20 gm V = 10 mL M = 10 gm V = 5 mL
Density = 20/10 = 2 gm/mL Cut the block in half M = 10 gm V = 5 mL Density = 10/5 = 2gm/mL

wood plastic rubber copper

How is denisty calculated?
AIM: Mass How is denisty calculated? Density = Volume M D V

M D V Denisty = Mass / Volume Mass = Density X Volume

Example #1: 1. What is the density of a metal block that has a mass of 525 gm and a volume of 50 cm3?

D = m v D = 525 gm 50 cm3 D = 10.5 gm/cm3

What is the block made of?
Silver = 10. 5 g/cm3

Example #2 The mass of a marble is 8.8 gm. It has a volume of 2 mL. What is it’s density?

D = m v D = 8.8 gm 2 mL D = 4.4 gm/mL

Example #1 M = 45gm D = 20.1 gm/mL Volume = ? M D V

V = M D V = 45 gm 20.1 gm/mL V = 2.2 mL

It’s density is greater than the density of water (1 gm/mL)
Will this object float or sink in water? Why? Sink It’s density is greater than the density of water (1 gm/mL)

Example #2 D = gm/mL V = 1.6 mL Mass = ? M D V

M = D x V M = 3.5 gm/mL x 1.6mL M = 5.6 gm