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 Forces of attraction between particles are strong when they are close together  Particles cannot flow in a solid b/c the force of attraction between them is too strong  Liquids and gases can flow because the molecules have enough energy to break the forces of attraction between the molecules 11

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Resistance and Aerodynamics 15

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 When comparing densities why is air less dense than liquids? 33 Liquids and gas

 When looking at two substances does it’s density change as it changes state?  Use the kinetic molecular theory to explain why it does.  What happens to the volume of a substance when heat is added or taken away? 34

35 Water is exception to the rule.

36  If you have two 300ml bottles full of water that are the exact same size and you freeze bottle one and not bottle two?  Will one bottle get bigger?  What the mass in each bottle stay the same?  Will the

Comparing Densities – Things to Remember 37  Each pure substance has its own characteristic density  Solids have greater densities (usually) than liquids, and liquids have greater densities than gases

What portion of an iceberg is submerged? 38

Calculate 39  Calculate the percentage of a piece of birch that would float on the surface of vegetable oil  Birch D = 0.66g/cm3  Oil D = 0.92g/cm3  Formula to find comparing densities  Density of solid / Density of liquid x 100 %  Would more or less of the birch float in water compared to oil?

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 How is buoyancy different that volume?  Try this  Lump a ball a clay and drop it in water watch how much water displaces  Turn that lump into a bowl and submerge into water see what happen. What did you notice. 41 Buoyancy

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Buoyant force = Weight in air (N) – Weight in liquid (N) For example if 300g or clay weighs 2.9N in the air and 1.6 N in water what is the buoyant force? 44

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 Buoyancy acts on objects immersed in a gas the same way it acts on objects immersed in gas – however there is ONE big difference between them  Density – the density of air is about 1/800 of that of water  You must displace a much greater volume of air to “float” in it 48

Buoyancy in WaterBuoyancy in Air 49

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 What happens to a substance when it’s mass stays the same but it’s volume increases?  What are the three types of bouyancy?  The density of air is _______ of that of water? Which means in order for something to float in air you must? 51 Let’s Recap

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 Viscosity is the resistance of a fluid to flow and move  Like in the oil lab when happen when heat is added to the oil? Think about the oil’s molecules  What happens when heat is taken away from the oil? Think about the oil’s molecules 53 Viscosity

 Density Is the mass of a substance per unit volume of a substance. D = M/V  Generally, what happens to a liquids density when we heat a substance?  Hint – think about it’s molecules, now think about it’s volume.  Generally, what happens to a liquids density when heat is removed? Again think of molecules and volume. 54 Density

55  As just discussed fluids run more easily when they are warm because molecules are able to slide past each other. Syrup!  Viscosity, density and buoyancy all change with changes in temperature  We also know that density changes as heat being added or removed affects it’s volume. Heat expand & cool shrinks.

Water Behaves Differently 56  Water is the only liquid that has a reverse effect only when you remove heat.  What happens as you remove heat from water?  Hint think of an ice cube in water.

57  Water behaves differently from other fluids when the temperature changes

Go into Skitch and Draw a picture of what molecules look like at 0ºC, 4ºC and 8º C 58