Fluids Review Test Friday

The many uses of fluids (p. 192-195) Read and understand the following concepts Fluids can transport solids Fluids can hold other materials Fluids can become solids Other uses for fluids (oil in a car, paint for iron to prevent rust, etc.)

The particle theory of matter (p. 197-200) Know the difference between matter, mass and volume Know that the particle theory of matter is a simple way of describing matter and its behavior - 6 points All matter is made up of tiny particles All particles are in constant motion All particles of one substance are identical Temperature affects the speed at which particles move In liquids and solids, the particles are close together and have strong forces of attraction between them In a gas, there are spaces between particles

Particle theory and properties of fluids Liquids and gases can flow Thermal expansion is an increase in the volume of a substance in response to an increase in its temperature

Viscosity and the effects of temperature (p. 210-213) Viscosity is the resistance of a fluid to flow Know how temperature affects the flow rate of a fluid Temperature changes in liquids Temperature of liquid increases, viscosity decreases Temperature changes in gases is different than it is in liquids Friction is a force that works to slow down motion as a result of surfaces rubbing against one another) As temperature of a gas increases, friction increases, and so the viscosity of the gas increases. The warmer the gas, the slower it flows.

Flow rate Flow rate of a fluid is a measure of the speed at which a fluid flows from one point to another Flow rate is determined by measuring the amount of fluid that flows past a given point in a given time.

Density (p. 213-218) Density is the amount of mass contained in a given volume Density describes how closely packed together the particles are in a substance Solid – most dense Gas - least dense

density Density of substance > Density of fluid = substance will sink Density of substance < density of fluid = float Density of substance = density of fluid = substance will hover A substance can have different densities depending on its temperature Warm water floats on the top of the water because it has a lower density than that of the cold water.

Calculating density Density (D) = Mass (m) / volume (v) We can rearrange this formula for both mass and volume

Comparing densities Review graph on page 218

Forces in fluid: buoyancy (page 219-221) A force is a push or pull that acts on an object. For example, weight is the amount of downward pull on an object due to the force of gravity. The measuring unit of force is the newton (N) Buoyancy is the tendency of an object in a fluid to rise or sink due to density difference with its surroundings. While earth’s gravitational force attracts matter downward toward earth’s center, a fluid has an opposite force that pushes matter upward. This upward force is called buoyant force.

Buoyancy and gravity An object will rise in a fluid when The density of the object is less than the density of the fluid The buoyant force on the object is greater than the force of gravity on the object An object will sink in a fluid when The density of the object is greater than the density of the fluid The buoyant force on the object is less than the force of gravity on the object An object will float in a fluid when The density of the object is equal to the density of the fluid The buoyant force on the object is equal to the force of gravity on the object

Archimedes’ principle The buoyant force on an object is equal to the weight of the fluid displaced by the object You must know different applications of buoyancy Sperm whale Hot air balloons

Changes in density of fluids (p. 221) Heavy ships sink lower in fresh water than salt water because the fresh water is less dense than the salt water. Heavy ships sink lower in warm water than cold water because the warm water is less dense than the cold water. Plimsoll line shows how heavily a ship can be safely loaded in different water conditions (p. 221)

Pressure in fluids (page 227-229) When you swim in water, you might noticed the pressure of the water around you, especially when you dive to the bottom of a pool Air pressure is also the reason why your ears may pop when you change altitude quickly. (when the pressure outside changes, the air pressure on the inside of your middle ear has to adjust, resulting in the pop). Pressure is the amount of force applied to a given area.

Changes in pressure (p. 228) Air pressure changes with altitude The layers of air in Earth’s atmosphere extend more than 160km above the earth’s surface Close to the surface, we experience air pressure as a result of all those air particles above us being pulled toward Earth by the force of gravity. There is less air pressure if we travel to higher altitudes because there are fewer layers of air above us and the air is less dense. You can view this effect on a weather balloon (expands as it rises, until it busts). Weather balloon: https://www.youtube.com/watch?v=dLpyTodmfg8

Pressure (depth, flow, temperature) (p. 228-229) The weight of water at the top of a pool presses down on the water in the lower parts of the pool. There is more pressure at the bottom. If fluid can move, it will always travel from an area of higher pressure to an area of lower pressure If the temperature of a fluid is increased, and if it is trapped inside a container, this leads to an increase in pressure. If the volume of the container cannot increase, its pressure increases, and this might result in an explosion (i.e. microwave).

Compression (p. 229) Compression is a decrease in volume caused by a force Compression socks Change in shape of a soccer ball when kicked Compressibility is the property of being able to be compressed. Materials in a liquid state are said to be incompressible which means they cannot be compressed easily.

Observation: Flow rate

Lab: Archimedes principle

Lab: foil boat