1. 2 3 4 5 6 7 8 9 10 Forces of attraction between particles are strong when they are close together Particles cannot flow in a solid b/c.

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Unit B – Fluids Chapter 4 – The Properties of

FluidsChapter 5 - The Use of FluidsChapter 6 – Fluids and Living

Things

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Chapter 4 – The Properties of Fluids

Key Ideas• FLUID FLOW IS IMPORTANT WHEN AN OBJECT IS MOVING THROUGH A

FLUID OR A FLUID AROUND AN OBJECT• FLUIDS CAN BE DESCRIBE USING THEIR PROPERTIES• THE KINETIC MOLECULAR THEORY CAN EXPLAIN THE BEHAVIOUR OF

FLUIDS• TEMPERATURE CAN AFFECT THE PROPERTIES OF FLUIDS

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4.1 – A Close-Up Look at Fluid Flow

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Fluids are things that flow – Gases & Liquids Fluids flow because some sort of force is pushing or

pulling them

FORCE – a push or pull that causes movement The most common force is the force of gravity

FLOW RATE – how quickly a fluid flows in a given amount of time

Fluids Flow

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Fluids Flow

Systems that involve movement, such as moving fluids, are said to be dynamic

Air or gas moving around solid objects is referred to as aerodynamics

Water or liquids moving around solid objects is referred to as hydrodynamics

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Solids That Seem to Flow

Some solids can be poured (powder, sand) and can appear to flow but these are not fluids

If it can form a pile – it is not a fluid

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The Kinetic Molecular Theory

All matter can exist in three states and can change from one state to another Solid Liquid

Gas

The Kinetic Molecular Theory is a model that helps us understand how matter can change from one state to another.

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Kinetic Molecular Theory

The Kinetic Molecular Theory states that:

1. All matter is made up of very small particles (molecules and atoms)

2. Particles are constantly movingI. Solids – particles packed so tight that they

can only vibrateII. Liquids- particles farther apart so they can

slide past each otherIII. Gases- particles very far apart, move

quickly3. There are forces of attraction among particles

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Kinetic Molecular Theory

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Temperature and Changes of State

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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

Explaining Flow Using the Kinetic Molecular Theory

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4.2 – Fluid Flow Around Objects

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Shape of an object determines how fluids flow around it

Laminar Flow- Flow in which a fluid travels in straight, or almost straight lines

Turbulent Flow- fluid flow characterized by irregular patterns when a fluid is unable to travel in straight lines

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Shape of an object determines how fluids flow around it

Drag- A force (air or water resistance) that acts to slow an object moving through a fluid.

Streamlined- shaped to create laminar flow, has less air or water resistance (less drag) also called aerodynamic

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Wind TunnelsResistance and Aerodynamics

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4.3 – Viscosity: A Property of Fluids

VISCOSITY- The resistance of a fluid to flowing and movement

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The Kinetic Molecular Theory helps us understand that resistance is due to the forces among particles

COHESION – The attractive forces among the particles of the same substance

The stronger the forces of attraction are, the greater the resistance of particles moving past one another

Viscosity

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ADHESION – The attractive forces between the particles of a fluid and the particles of another substance The reason why ketchup sticks to the sides of a

bottle

Viscosity

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SURFACE TENSION

In liquids, the attractive forces among the particles at the surface are greater than the attractive forces among the particles deeper in the liquid – this is called surface tension

SURFACE TENSION– The increased attraction among the particles at the surface of a liquid

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An Instrument that measures viscosity is called a viscometer

Measuring Viscosity

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4.5 – Measuring Matter: Mass, Weight, & Volume

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Mass– the amount of material in an object An object’s mass stays constant everywhere in the

universe Mass is measured in grams (g) (kilo, milli, micro)

Weight– a measurement of the force of gravity pulling on an object An object’s weight varies depending where it is in the

universe Weight is measured in Newtons (N)

Mass & Weight

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Mass vs. Weight

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Volume– a measure of the amount of space an object occupies. It is measured in cubic meters, cubic centimetres,

litres, or millilitres

Meniscus– curved surface where a liquid contacts the wall of a container Forms due to the adhesive forces between the fluid

and the container

Volume

Measuring Volume

Measuring the Volume of a Liquid: You can measure a small

volume in a graduated cylinder

Remember to read the volume from the bottom of the meniscus at eye level

Measuring Volume

Calculating the Volume of a Rectangular Solid: Volume = length x width x

height

If you measure all the sides in centimetres then the volume will be in cubic centimetres (cm3)

*REMEMBER* - one cm3 = one mL

Measuring Volume

Calculating the Volume of an Irregular Solid: Use technique called DISPLACEMENT

Volume of solid = (volume of water + solid) – volume of water

Measuring Volume

Calculating the Volume of an Irregular Solid

4.7 – Density: Another Property of Fluids

DENSITY – Mass per unit volume of a substance

Using Density

It is expressed as grams per cubic centimetre (g/cm3) or grams per millilitre (g/mL)

Density is calculated by dividing the mass of an amount of a substance by its volume.

Density= mass/volume or D=m/V

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Density is a Property of Fluids and Solids

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4.9 – Comparing Densities

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When comparing densities why is air less dense than liquids?

Liquids and gas

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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?

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Water is exception to the rule.

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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

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Comparing Densities – Things to Remember

Each pure substance has its own characteristic density

Solids have greater densities (usually) than liquids, and liquids have greater densities than gases

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What portion of an iceberg is submerged?

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Calculate

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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4.10 – The Ups and Downs of Buoyancy

The volume of fluid displaced is equal to the volume of the object in

the fluid

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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.

Buoyancy

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Buoyancy

Buoyancy – The upward force that a fluid exerts on an object

Buoyancy is not the only force that acts on an object in a fluid – The force of gravity (weight) also acts on the object

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Archimedes Principle

Archimedes Principle – the buoyant force on an object immersed in a fluid is equal to the weight of the fluid that the object displaces

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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?

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4.11 – How and Why Do Things Float?

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Positive Buoyancy- the tendency of an object to float or rise in a fluid because the object weighs less than the fluid it displaces

Neutral Buoyancy- The tendency of an object to remain at a constant level in a fluid because the object weighs the same as the fluid it displaces

Negative Buoyancy- the tendency of an object to sink in a fluid because the object weighs more than the fluid it displaces.

Forces Acting on a Floating Object

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Forces Acting on a Floating Object

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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

Buoyancy in Air

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Buoyancy in Air

Buoyancy in Water Buoyancy in Air

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Plimsoll Lines

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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?

Let’s Recap

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4.12 – How Does Temperature Affect

Viscosity and Density?

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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

Viscosity

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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.

Density

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How Does Temperature Affect Viscosity and Density?

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.

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Water Behaves Differently

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.

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Water: A Special Case

Water behaves differently from other fluids when the temperature changes

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Go into Skitch and Draw a picture of what molecules look

like at 0ºC, 4ºC and 8º C