1. C HAPTER 11.1 AND 11.2 G UIDED R EADING A NSWERS

2. 1. What is pressure? It refers to a force exerted on a surface. 2. How is pressure and force related? PRESSURE decreases as the area over which a FORCE is distributed increases. 3. How does surface area affect pressure? The larger the area over which the force is distributed, the less pressure is exerted. 4. What is the equation for pressure? Pressure= Force/ Area 5. What are two units for pressure? Pascal (Pa)

3. 6. What is a fluid? A material that can easily flow. 7. What is fluid pressure? All of the forces exerted by the individual particles in a fluid combine to make up the pressure exerted by the fluid. 8. Why does air exert pressure? Air exerts pressure bc it has mass. 9. What is the mass of a cubic meter of air? 1.28kg 10. Why does air pressure not crush your body? Your body contains fluids that exert outward pressure. The weight of the atmosphere does not just press down on your hand. It presses on your hand from every direction.

4. 11. How is the pressure on your hand balanced? The weight of the atmosphere does not just press down on your hand. It presses on your hand from every direction. The pressures balance each other. 12. What happens when air pressure becomes unbalanced? A change will take place in order to stabilize the pressure. 13. Why do your ears pop? At higher elevation, there is less air above you and therefore less air pressure. As your elevation increases, atmospheric pressure decreases. Your ears pop to help stabilize the pressure. 14. What happens when your elevation is increased? Atmospheric pressure decreases. 15. What happens to water pressure as you descend? Water pressure increases.

5. 16. What is a barometer? An instrument used to measure atmospheric pressure. 17. What are 2 types of barometers? Mercury barometer and aneroid barometer. Aneroid barometer is the one you usually see hanging on a wall. 18. What does decreasing pressure mean? A storm is on the way! 19. What does increasing pressure mean? A sign of fair weather!

6. Do Math practice 4 and 5 on page 378 4. Find the area of a rectangle photo that is 20cm long and 15 cm wide. 20cm X 15xm = 300cm 2 5. Which has a greater area: a square table that measures 120cm X 120cm, or rectangular table that measures 200cm X 90cm? 120cm X 120cm = 14,400cm 2 200cm X 90xm = 18,000cm 2 Therefore the rectangle has a greater area.

7. 11.2 1. What is buoyancy? The tendency of an object to float. 2. What is buoyant force? An upward force. 3. Why does it make objects feel lighter? Buoyant force acts in the direction opposite to the force of gravity, so it makes an object feel lighter. 4. When does an object sink? Force of weight > buoyant force. 5. When does an object float? Buoyant force > force of weight

8. 6. Who was Archimedes? Greek mathematician 7. What is Archimedes principal? State that the buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces. 8. Why does a ship float? A large object displaces more fluid than a small object. A greater buoyant force acts on the larger object. 9. What is density? Mass per unit volume. 10. What is the equation for density? Density = mass/volume

9. 11. How does density help us tell if something will sink or float? An object that is more dense than the fluid in which it is immersed will sink. An object that is less dense than the fluid in which it is immersed will float. 12. How do submarines change density? Changing the water level in the flotation tanks changes the weight of the submarine. The submarine dives when its weight is greater than the buoyant force and rises when its weight is less. 13. Why does a helium balloon fly into the air? Helium gas is less dense than air.

10. 14. Calculate the density of each of the following:( show all work) A. 252 mL of a solution with a mass of 500. g D= m/v 500/252 = 1.98g/ml B. 252 mL of a solution with a mass of 500 g D= m/v 500/252 = 1.98g/ml C. A 6.75 g solid with a volume of 5.35 cm 3 D= m/v 6.75/5.35= 1.26 g/ cm 3 D. 50.0 mg of a gas which occupies a volume of 0.0064 L D= m/v D= 50.0/.0064= 7812.5 mg/L