 # How tightly the atoms are packed together in an object

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How tightly the atoms are packed together in an object
Density How tightly the atoms are packed together in an object

Density At the conclusion of our time together, you should be able to:
Define density Calculate the density of a given object if given the volume and mass Calculate the volume or mass if the density is given with the volume or mass

Density Density = mass volume Mass = the amount of matter in an object
Volume = the amount of space the object takes up Units = g/mL (liquid) OR g/cm3 (solid)

DENSITY - an important and useful (qualitative) intensive physical property
Aluminum Platinum Mercury 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

Density Calculations M D V Cover up whatever unit you are solving for, the two units remaining will show you how to solve the problem.

Density Calculations Regularly Shaped Solid : mass = balance
volume = measure (l x w x h) Irregularly Shaped Solid: volume = water displacement

mass = tare graduated cylinder, mass liquid

Problem A piece of copper has a mass of 57. 54 g. It is 9
Problem A piece of copper has a mass of g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3). M D V

Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.

1. Get dimensions in common units.
SOLUTION 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3 Note only 2 significant figures in the answer!

DENSITY Density is a (qualitative) intensive property of matter.
does NOT depend on quantity of matter. like temperature Contrast with (quantitative) extensive property depends on quantity of matter. like mass and volume. Styrofoam Brick

Problem: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?

Strategy First, note that 1 cm3 = 1 mL
1. Use density to calculate mass (g) from volume. 2. Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb

Strategy 1. Convert volume to mass 2. Convert mass (g) to mass (lb)

Learning Check Osmium is a very dense metal. What is its
density in g/cm3 if g of the metal occupies a volume of 2.22 cm3? 1) g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = g = volume 2.22 cm3 = g/cm3 = g/cm3

Learning Check Osmium is a very dense metal. What is its
density in g/cm3 if g of the metal occupies a volume of 2.22 cm3? 1) g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

Volume (H2O) Displacement
A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

Learning Check What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm ) 6 g/cm ) g/cm3 33 mL 25 mL

Liquid Layers If you pour together liquids that don’t mix and have different densities, they will form liquid layers. The liquid with the highest density will be on the bottom. The liquid with the lowest density will be on the top. Objects or substances with MORE density will sink below objects or substances with LESS density Which do you think is MORE dense, Water or Oil???

Water, Oil…and a Superball
The oil is less dense than the water, so it’s on top. The superball is less dense than water, but more dense than oil, so it sinks to the bottom of the oil layer, yet floats on the top of the water layer.

The density of five liquids are measured as follows:
Liquid 1: 1.0 g/mL Liquid 2: 1.38 g/mL Liquid 3: 0.77 g/mL Liquid 4: 2.95 g/mL Liquid 5: g/mL Draw a picture of all 5 liquids in a test tube how they would layer according to density Liquid 5 Liquid 3 Liquid 1 Liquid 2 Liquid 4

Liquid Layers Check out this picture. Which layer has the highest density? Which layer has the lowest density? Imagine that the liquids have the following densities: 10g/cm3. 3g/cm3. 6g/cm3. 5g/cm3. Which number would go with which layer? 3 g/cm3 5 g/cm3 6 g/cm3 10 g/cm3

Density Let’s see if you can:
Define density Calculate the density of a given object if given the volume and mass Calculate the volume or mass if the density is given with the volume or mass

Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) ) ) K V W V W K W V K

Learning Check The density of octane, a component of gasoline, is g/mL. What is the mass, in kg, of 875 mL of octane? 1) kg 2) 614 kg 3) 1.25 kg

Learning Check If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) L 2) L 3) L 4) 548 L

Learning Check A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.00 pound of aluminum, how many liters of aluminum (D = 2.70 g/cm3) are obtained from the cans? (1 kilogram = 2.2 pounds) 1) L 2) L ) L

Which is heavier, a quart of water or a quart of mercury?
Water has a density of 1.0 g/ml and mercury (Hg) has a density of 13.6 g/ml. Which is heavier, a quart of water or a quart of mercury? If we have equal volumes of two different substances, then the one with the greater density will have the greater mass.

Which is heavier, a ton of feathers or a ton of bricks?
Neither Which is larger? Feathers If two objects have the same mass, the one with the higher density will be smaller.

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