# Focus On Physical Science: California Grade 8

## Chapter 3: Densityand Buoyancy

### Standards Review

 1. How does the density of 25.0 g of a substance compare with the density of 5.0 g of the same substance? 8.a A) The densities are the same. B) The density of 25-g sample is 5 times larger. C) The density of the 25-g sample is twice as large. D) The density of 25-g sample is 5 times smaller. 2. Which is not a unit for density? 8.a A) kg/m3 B) km/m3 C) g/cm3 D) g/mL 3. How is the density of an object calculated? 8.b A) Add the mass of the object and its volume. B) Divide the volume of an object by its mass. C) Divide the mass of the object by its volume. D) Multiply the object's mass by its volume. 4. What is the density of an object whose mass is 15.0 g and whose volume is 5.0 cm3? 8.b A) 75.0 g/cm3 B) 3.0 km/m3 C) 0.33 g/cm3 D) 3.0 g/cm3 5. Density is a physical property because it can be measured without changing the _______ of a material. 8.a A) mass B) volume C) composition D) weight 6. The formula V = lwh is used to calculate the volume of what type of object? 8.b A) irregular solid B) rectangular solid C) sphere D) cylinder 7. What causes the upward buoyant force on an object placed in a fluid? 8.c A) The pressure exerted by the fluid is the same at all depths. B) The pressure exerted by the fluid increases with depth in the fluid. C) The pressure exerted by the fluid is always upward. D) The pressure exerted by the fluid on all sides of the object is balanced. 8. What must be true for an object to float? 8.c A) The mass of the object equals the buoyant force. B) The object's weight is greater than the buoyant force. C) The object's volume equals the volume of fluid displaced. D) The buoyant force equals the object's weight. 9. What is Archimedes' principle? 8.c A) The pressure on an object equals the weight of the fluid the object displaces. B) The buoyant force on an object equals the volume of the fluid the object displaces. C) The buoyant force on an object equals the weight of the fluid the object displaces. D) The pressure on an object equals the density of the fluid. 10. According to Archimedes' principle, an object floats if _______. 8.c A) The weight of the object equals the weight of the fluid displaced. B) The weight of the object equals the volume of the fluid displaced. C) The volume of the object equals the volume of the fluid displaced. D) The mass of the object equals the weight of the fluid displaced. 11. What will happen if the density of an object placed in a fluid is greater than the density of the fluid? 8.d A) The object will sink downward in the fluid. B) The object will float on top of the fluid. C) The object will rise upward in the fluid. D) The object will float below the surface of the fluid. 12. The depth to which a hydrometer sinks in fluid depends on the _______. 8.d A) weight of the fluid B) mass of the fluid C) volume of the fluid D) density of the fluid 13. What is the mass of an ice cube with a density of 0.92 g/cm3 and a volume of 5 cm3? 8.b A) 0.18 g B) 5.4 g C) 4.6 g D) 4.08 g 14. A hydrometer sinks twice as deep in a certain fluid as it does in water. This means that _______. 8.d A) the density of the fluid is twice the density of water. B) the density of the fluid is one half the density of water C) the volume of the fluid is one half the volume of water. D) the volume of the fluid is twice the volume of water. 15. A balloon rises in air because _______. 8.d A) the weight of the balloon equals the buoyant force on the balloon B) the density of the balloon equals the density of air C) the weight of the balloon is greater than the weight of the air the balloon displaces D) the density of the balloon is less than the density of air