Unit A – Mix and Flow of Matter Concept 3: Properties of gases and liquids (viscosity, density, buoyancy, compressibility)

FluidThickerThinner

Viscosity All fluids can move and flow A fluid’s VISCOSITY is how quickly and easily that fluid flows The particles of a fluid can roll over each other and slide past one another The harder it is for them to do this (friction), the higher the viscosity of that fluid HIGH VISCOSITY = “THICKER” FLUIDS (ketchup) LOW VISCOSITY = “THINNER” FLUIDS (juice)

Viscosity and Temperature What happens to honey when it is heated up? When heat or energy is added to a fluid, the movement of the particles increases This allows them to slide around easier Therefore, heating a fluid DECREASES its viscosity Cooling a fluid INCREASES its viscosity

Cars need engine oil in order to run. What is one problem we have in Canada related to engine oil and viscosity?

The Ramp Method One method of testing viscosity is by pouring a fluid down a ramp and timing how long it takes to get to the bottom In your Science Log, rank the following substances from LEAST to MOST viscous… Ketchup, Syrup, Shampoo, Vegetable Oil, Water

Density Density is the amount of matter within a given volume of a substance The density of a fluid depends on what kind of particles are in a substance, as well as how closely packed together they are

Calculating Density Density is the mass per unit volume Calculate density by DIVIDING THE MASS OF A SUBSTANCE BY ITS VOLUME (mL or cm 3 ) 2.0 mL of mercury has a mass of 27.1 grams. What is the density?

Calculating Density 0.5 mL of silver has a mass of 5.25 g. What is the density? 2.5mL of lead has a density of 11.4 g/mL. What is the mass?

Calculating Density A substance with a mass of 0.8g has a density of 3.2g/mL. What is the volume? A substance has a volume of 10mL, and a density of 4.6g/mL. What is the mass?

Density and Temperature Lets think about a block of ice… what happens to the particles within the solid as heat (energy) is added? Particles in a substance move faster as energy is added This also means that the distance between particles increases as they become more active How does this affect Density??

Density and Concentration Dissolving one substance in another results in more particles in a certain volume Distilled water has a density of 1g/mL What happens when we dissolve salt in 1 mL of water? Because this lake is salt water, it is denser than human bodies. Therefore, we can float!!

Buoyancy We have seen that objects sink when they are more dense than fluids they are placed in because of the pull of gravity However, on the other hand, objects are also pushed up by the buoyant force of liquids BUOYANCY is the tendency of an object to float when placed in a liquid When the density of the liquid is greater than the object, the buoyant force of the liquid keeps it afloat

Compressibility As we have seen, fluids can be compressed This also means that they can transmit pressure SCIENCE LOG Why does the Water flow out of The can this way?

Pressure Pressure is the amount of force applied to a given area, and is measured in pascals (Pa) If we apply a force of 1 Newton (1N) over an area of 1 m 2, this will equal 1 Pa Pressure (p) = Force (F) / Area (A) = 1N/1m 2 = 1 Pa What is the pressure of 20 N acting on an area of 5m 2 ??

Pressure What is the pressure of 20N of force acting on an area of 8m 2 ? A pressure of 20 Pa is felt on an area of 5m 2. What is the force applied?

Pascal’s Law Blaise Pascal began to experiment with fluids in enclosed systems He developed what is now called Pascal’s Law, which states that an enclosed fluid transmits pressure equally in all directions This law is crucial for many machines we use daily, such as hydraulics and pneumatics