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Chapter 5.8 Density Mrs

Chapter 5.8 Mrs. Baldessari

Objective: You will define and calculate density with appropriate units.

1 Density

 Take a look at the two boxes below. Each box has the same . If each ball has the same , which box would weigh more? Why?

2 Density

 Answer: The box that has more balls has more mass per .

 This property of is called density. The density of a material helps to distinguish it from other materials.

 Density d = mass/volume (g/ml)

3 Density

 Calculate the density of each block.

Block I Block II Mass = 79.43 Mass = 25.41 grams Volume=29.8 ml Volume = 29.8 ml

4 Density

 Block I – Density = 79.43 grams / 29.8 ml = 2.67 g/ml

 Block II – Density = 25.41 grams / 29.8 ml = 0.853 g/ml

5 Density units

Density compares the mass of an object to its volume

D = mass = g or g volume mL cm3

Note: 1 mL = 1 cm3 6

Density

 Density is a physical characteristic of a material and allows us to determine what each block is made of.

 All pieces of matter made of the same material will have the same density.

 Different matter will have different .

7 Example #1

A certain has a mass of 17.8 g and a volume of 2.35 cm3. What is the density of this mineral? mass Density = volume 17.8 g Density = 2.35 cm3

Density = 7.57 g/cm3

9 Example #2

•What is the mass of a 49.6 mL sample of a , which has a density of 0.85 g/mL?

mass •Cover the variable that your are Density = volume solving for x •Perform the math operation as it is 0.85 g/mL = shown in the triangle 49.6 mL

mass = x = 42 g m m=(D)(V) D v 10

Concept Check

Copper has a density of 8.96 g/cm3. If 75.0 g of is added to 50.0 mL of in a graduated , to what volume reading will the water level in the cylinder rise?

a) 8.4 mL b) 41.6 mL c) 58.4 mL d) 83.7 mL 11 Having trouble with the math?

• Cover the variable that your are solving for m •Perform the math operation as it is shown in the triangle d v

12 Volume Displacement A displaces a matching volume of water when the solid is placed in water.

33 mL

25 mL

13 Learning Check What is the density (g/cm3) of 48 g of a if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3

33 mL

25 mL

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2) 6 g/cm3 Volume (mL) of water displaced = 33 mL - 25 mL = 8 mL

Volume of metal (cm3) = 8 mL x 1 cm3 = 8 cm3 1 mL

Density of metal = mass = 48 g = 6 g/cm3 15 volume 8 cm3

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) 2) 3)

V W K K V W K V W 16

Solution

(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL)

1) V

W K 17 Density Connections

Mass Volume

kg L

g mL (cm3)

mg 18 Learning Check

The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? 1) 0.614 kg

2) 614 kg

3) 1.25 kg

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Solution

1) 0.614 kg Unit plan: mL  g  kg

Equalities: 1 mL = 0.702 g and 1 kg = 1000 g

Setup:

875 mL x 0.702 g x 1 kg = 0.614 kg 1 mL 1000 g density metric factor factor 20 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) 0.548 L 2) 1.25 L 3) 1.83 L

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Solution

1) Unit Plan: g mL L

575 g x 1 mL x 1 L = 0.548 L 1.05 g 1000 mL 22

Learning Check

A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 of aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans? Note, 1 mL = 1 cm3

1) 1.0 L 2) 2.0 L 3) 4.0 L

23 Solution

1) 1.0 L

125 cans x 1.0 lb x 454 g x 1 cm3 21 cans 1 lb 2.70 g

x 1 mL x 1 L = 1.0 L 1 cm3 1000 mL

24 Learning Check

You have 3 metal samples. Which one will displace the greatest volume of water? 1 2 3 25 g Al 45 g of 75 g of 2.70 g/mL 19.3 g/mL 11.3 g/mL

25 Discuss your choice with another student. Solution

1) 25 g Al x 1 mL = 9.2 mL 2.70 g

25 g Al 2.70 g/mL

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