Fluids and DynamicsUnit 3

Science 8Tannant

Chapter 7

Kinetic Molecular Theory Explains The Characteristics of Solids,

Liquids, and Gases

7.1 States of Matter

Matter—anything that has mass and volume

Mass = amount of ‘stuff’ or particlesVolume = space or size

Example

The Basketball has greater volume, but the bowling ball has greater mass.

The Particle Model

1. All matter is made of particles.

ATOMS

2. There are spaces between the particles.

The amount of space is different for each state of matter.

3. The particles are ALWAYS moving.

The more ENERGY particles have, the more they move.

4. Particles are attracted to other particles.

The strength of attraction depends upon the type of particles.

Strong attraction = particles mix

Weak attraction = particles separate

Kinetic Molecular TheoryKinetic = motion (energy)

Molecules (or atoms) are the particles in matter.

KMT = the THEORY that explains how matter behaves when the energy of particles changes and allows you to predict those behaviors.

The KMT and Particle Theory are almost identical.

Particle Theory of Matter Kinetic Molecular Theory

1 All matter is made up of particles.

1. All matter is made up of atoms and molecules.

2. There are spaces between particles.

2. There is empty space between particles.

3. Particles are always moving. 3. Particles are always moving—they collide with each other and the sides of their container.(a) Solids = vibrate(b) Liquids = slide past each other(c) Gases = move quickly and are far apart from

each other4. Particles are attracted to each other.

4. Energy makes particles move. The more energy they have, the faster they move and the farther they move apart.

Thermal Expansion

As the heat (ENERGY) increases, The particles move faster and farther apart The substance EXPANDS.

Thermal ContractionAs a substance LOSES energy, the particles move slower,

and move closer together causing the substance to get smaller

(decrease volume)

Contraction and Expansion

The Difference Between Heat and Temperature

Kinetic Energy = Energy of MOTION

When particles heat up, they have more energy and MOVE more…

So—Kinetic Energy is also THERMAL energy (or Heat energy)

Thermal Energy• The total amount of kinetic

energy in a substance.

Energy Flow

• If two substances with DIFFERENT thermal energies come into contact, the energy will ALWAYS flow from an area of HIGH energy to an area of LOW energy.

[High Low]

Heat

• The energy transferred from one type of matter to another

(As a result of a difference in temperature or a change in state.)

Temperature

• The AVERAGE kinetic energy of all a substances particles.

Energy Transfer and Heat Flow

Changes in State occur due to Changes in Energy

Melting

• Change in state from a solid to a liquid• Energy is added• Particles spread out and slide/flow past each

other.

Melting point

• The temperature at which a solid changes state to a liquid.

• Although energy is added—there is NO change in temperature

• Example: The melting point (or freezing point) of water is 0˚C.

The melting point and freezing point are the same thing!

Evaporation

• Change of state from a liquid to a gas• More energy is added• Particles move rapidly and spread apart

Boiling Point

• The temperature at which a liquid changes state to a gas.

• Although energy is added, the temperature remains constant.

• Example: The boiling point of water = 100˚C

Condensation

• Change in state from a gas to a liquid• LOSS of energy—particles move

slower and get closer together.

Solidification/Freezing

• Change of state from a liquid to a solid.• LOSS of energy—particles slow down

(vibrate only) and get as close as possible together (contract)

Sublimation

• Direct change of state from solid to a gas

• Example: Dry ice

Deposition

• Direct change of state from a gas to a solid• Example: Frost

Change of State versus Temperature

7.2 Fluids and Density

Fluid• Any form of matter that can flow (particles

slide past each other)

•Liquids and Gases ONLY

Density

• A property of matter

• The amount of MASS contained in a given VOLUME.– How closely packed the particles are

Less dense particles ‘float’ on denser particles

Density and KMT

• As particles heat up they move faster….• As they move faster, they have more space

between them…• The more space = LESS DENSE, so they ‘float’

Expansion

• When substances heat up and particles expand (less dense)

Contraction

• When substances cool down and particles move closer

• More dense

Water—the Exception

• Water is densest at 4˚C.• As water cools lower than 4˚C, the particles

form rigid bonds that cause the water to expand!

• That’s why ice floats!

Water Particles

Density

• Generally, solids are denser than liquids, and liquids are denser than gases.

• There are SOMEexceptions…

Density Chart for Pure Substances

Pay attention to units

g/mL—liquids or gases

g/cm3 –solids

Comparing DensityLayering different substances works well to compare density

Measuring Density

To measure density, we must measure both the SIZE (volume) of the substance and its MASS (weight)

Volume

Volume = height x length x width

Measured in mL or cubic cm (cm3)

Volume Displacement

• Volume can also be recorded by the amount of water displaced by an object.

Meniscus Measurement

Using a Graduated Cylinder

Measuring Mass

Calculating Density

1 mL of glycerol has a mass of 1.26 g. What is the density of glycerol?

Use the formula: D = m/v1.26g 1 mL

= 1.26 g/mL Density

What is the density of a 2 cm^3 sugar cube that has a mass of 3.18 g?

A 3 mL sample of oil has a mass of 2.64 g. What is the density?

Look on the density chart on p.262.

Which is more dense, lead or iron?How do you know?