1. Properties of Fluids Objective 4 IPC 7A Investigate and identify properties of fluids (gases and liquids) including density, viscosity, and buoyancy.

2. Density is the ratio of mass to volume. Mass is measured in grams (g). Volume is measured in mL (for liquids) or cm 3 (for solids). D = mass/volume = grams/mL or grams/cm 3 MASS = amount of matter in an object VOLUME =amount of space an object takes up

3. Density is defined as the mass of a substance divided by its volume. D = m/V, m is the mass of the object, V is its volume. More dense liquids will sink in the presence of less dense liquids.

4. If you’ve ever carried bags of groceries, you know that some bags have greater mass than others, even though the volumes of the bags are the same. Mass and volume are general properties of all matter. So density is also a property of all matter. The density of a specific kind of matter helps to identify it and to distinguish it from other kinds of matter. Density

5. The density of a piece of matter is a combination of how compressed the material is and the mass and volume of its atoms or molecules. Which has a greater density: water or steam? Explain your choice. Water is more dense because the molecules are closer in water than they are in steam.

6. Why should the density of an object be the same on the Moon as on earth. Since density is related to the mass of an object, the density of a given volume of lead would be the same on both the Earth and the Moon, although the lead would weigh less on the Moon because of the lower gravity there.

7. As temperature is increased (or decreased) there is no change in the mass of an object. However, since substances generally expand as they are heated, the volume will increase with an increase in temperature. This increase in temperature will cause the density to decrease. Why are hot air balloons heated before they float?

8. Heating the air in the balloons causes the air to increase in volume, making the density decrease. When the density of the air in the balloon is less than the air outside the balloon, it floats.

9. Typically, when you freeze a liquid, its atoms or molecules get closer together, such that the solid is more dense than the liquid. An exception to this is when you freeze water. When ice is formed, it actually expands, thus making it less dense than water. The water molecules bond together in an open hexagonal shape.

10. Gases have low densities and variations in pressure can be observed. The air pressure in a typical room is the same everywhere, but it is much lower at the top of a mountain than at sea level. Its density decreases with increasing altitude. Why do you think this is true? There is less pressure on the air at the top of a mountain so the molecules of air spread out more, decreasing the density.

11. Gas pressure is influenced by four things 1. The amount of gas present As the number of gas particles increase in a container increases the volume increases proportionally. (Think of blowing up a balloon) 2. The temperature of the gas An increase in the temperature of a gas increases the volume of the gas proportionally. 3. The volume of the gas. The volume of a gas increases with an increase in temperature or decreases with a increase in pressure. 4. The pressure on the gas. The pressure of a gas increases with an increase in temperature, decreases with an increase in volume, and increases with an increase in the amount of gas present.

12. Did you know that 90% of an iceberg lies below the water? Why is that? What determines whether something sinks or floats, and, if it floats, how much of it remains above the surface?

13. Buoyancy! Buoyancy is the ability of a fluid (a liquid or a gas) to exert an upward force on an object immersed in it. It is controlled by differences in density between the object and the fluid.

14. Two important forces are in play when Surfing: Buoyancy and Gravity: The water exerts its buoyant force on the surfboard.The weight of the surfer and board give a downward force due to gravity. When the forces are equal the surfer and board float.

15. Whether an object floats or sinks, is based on not only its weight, but also the amount of water it displaces. That is why a very heavy ocean liner can float. It displaces a large amount of water. When the weight of the displaced water (the buoyant force) equals the weight of the ship, it floats. Buoyant force Weight of ship

16. When an object displaces a fluid it is basically pushing the fluid out of the way. Objects will push the fluid out of the way until the weight of the displaced fluid equals the weight of the object.

17. A block of wood made of oak, for example, sits deeper in the water (and therefore displaces more of the water) than does a block of pine. The reason is that it's heavier for its size, or denser -- in this case, the molecules that make it up are more closely packed together than the molecules that make up the pine.

18. But what about the buoyant force for an object that sinks???? The weight of the water displaced is less than the weight of the object, so it sinks.

19. A standard hot air balloon has a volume of 1590 cubic meters (56,000 cubic feet) which is larger than the average house. How can it fly? [Hint: relate to buoyancy]

20. Gases are fluids, therefore an object in air also experiences an upward force equal to the amount of weight of air displaced. If the upward force exceeds the weight of the balloon, the balloon and its contents it will rise.

21. Viscosity is a property that is often called on when liquids need to be classified. Each liquid has a different viscosity, or resistance to flow. Peanut butter has a much higher resistance to flow than milk, and thus it has a much higher viscosity than milk. We like ketchup that has a high viscosity. Likewise, motor oil is more viscous than gasoline.Viscosity

22. Viscosity is a measure of the ease with which molecules move past one another. Viscosity depends on the attractive force between the molecules. Viscosity decreases with increasing temperature - the increasing kinetic energy overcomes the attractive forces holding the molecules together, so the molecules can more easily move past each other.

23. The viscosity of a given liquid is due to: the shapes of the molecules the attractive forces present between the molecules. Substances with a high viscosity typically have both of these characteristics. The polar ends of the molecules attract each other, while the long structures of the molecules "get tangled" with other molecules. A viscous liquid is somewhat like a tank of snakes with each snake biting another snake’s tail, and each snake’s body wrapped around another snake’s body.