Unit 1-5 Density

1. Unit 1-5 Density

2. physical and chemical properties • Matter has both physical and chemical properties. Physical properties: • are the characteristics of a substance that do not involve changing to another substance. • they are physical characteristics that can be observed or measured without changing the identity of a substance • Examples are: melting point, boiling point, shape, size, color, conductivity, solubility, hardness

3. 2 types of physical properties • Extensive- depends on the amount of matter • Ex: volume, mass, amount of energy, …. • Intensive- does not depend on the amount • Ex: color, odor, density, boiling point, ability to conduct ….

4. Platinum Mercury Aluminum DENSITY - an important and useful physical property 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

5. Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

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

7. 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!

8. Learning Check Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

9. Solution Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 = 22.5 g/cm3

10. How about the object with an irregular shape? Archimedes of Syracuse and the crown

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

12. 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/ cm3 2) 6 g/m3 3) 252 g/cm3 33 mL 25 mL

13. 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

14. Float or not float? • At normal temperature, the density of water is close to 1 g/mL. • principle of buoyancy : • If density of object> 1 g/ml, sink in water • If density of object< 1 g/ml, float in water • What about density of object= 1 g/ml? • Can you swim?

15. 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) K W V V K W W V K

16. 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

17. Learning Check A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D=2.70 g/cm3) are obtained from the cans? 1) 1.0 L 2) 2.0 L 3) 4.0 L

18. Homework • Page 40 question 61-66 • Due tomorrow.