chapter 8 solids, liquids, and gases

Chapter 8 Solids, Liquids, and Gases

Objectives

• 8.1 Describe the four states of matter • 8.1 Use the kinetic theory of matter to explain

the characteristics of solids, liquids, and gases • 8.1 Explain the thermal expansion of matter

Objectives

• 8.2 Describe how people use and pollute water

• 8.2 Discuss how people can save water and stop pollution

• 8.3 Interpret state changes in terms of the kinetic theory of matter

• 8.3 Account for the energy of the heats of fusion and vaporization in state changes

States of Matter• Solid

– Fixed Volume, Fixed Shape, Incompressible, Strong Forces

• Liquid– Fixed Volume, Flexible

Shape, Incompressible, Weak Forces

• Gas– Flexible Volume, Flexible

Shape, No Forces

States of Matter

• Dictated by – Temperature

• Higher Temperatures favor Gas– Pressure

• Higher Pressures favor solids– Forces present between matter

• Large forces favor solids

• Kinetic Theory of Matter: Tiny particles (that make up matter) are constantly in motion.

States of Matter

• Which state of matter has the most energy at room temperature? – Is it the table (solid)?– Is it the water (liquid)?– Is it the air (gas)?

State of Matter

• All states of matter have the same amount of energy– Temperature is a measure of kinetic energy. As

long as two substances have the same temperature, they have the same amount of energy

– The table molecules are larger, move slower– The air molecules are smaller, move faster

Solids

• Two types– Crystalline Solids

• Repeating Pattern– Amorphous Solids

• No form, no repetition

Examples

• Crystalline Solids– Salts, snowflakes

• Amorphous Solids– Wax, plastics, glass– Some people consider these to be “thick liquids”

Liquids

– Close together, but able to move freely around one another

• Incompressible but able to change shape

Gases

– Very far apart, no attraction to other molecules– Expand to fill volume– Very variable density (can be compressed)

• To put the gas in perspective: Water as a liquid, compared to water as a gas. The liquid water is 1200x more dense

Plasma

• State of matter where the particles become charged (ionized). – The nucleus is separated from some of the

electrons• Most common state of matter in universe,

(99%) of universe– The sun

• Has to be very hot– Not in your stove, try a few million degrees

Thermal Expansion

• As substances heat up, they increase in size– Kinetic Theory: If the molecules move more, they

take up more space. – If a kid eats a donut, they take up more space…

• Bridges (gaps), Thermometers (liquid expands), Houses creak at night (as they shrink in size)

Thermal Expansion

• Leads to convection in boiling water • Leads to gases having very different densities

– Think Hot Air Balloons• Caused the St.Louis Arch to not fit the first

time– Called up the Fire Department

Water Pollution and Water Issues

• How much water do we use on a daily basis?• What/who are the culprits for polluting

water?• How clean is USA drinking water anyway?• Is there enough fresh water to go around?• Should our water usage be more regulated?

Phase Changes

• When a substance changes state of matter, it is called a phase change

• The molecules don’t change, they just change how they are bonded– If you boil water, you are not changing the water into

another substance, it is still water• Does freezing take energy or release energy?• How do orange farmers keep the crops safe

when it is cold?

Changes of States

• Solid to Liquid Melting• Solid to Gas Sublimation

– Dry Ice and Moth Balls• Liquid to Gas Evaporation• Gas to Liquid Condensation• Gas to Solid Deposition

– Frost• Liquid to Solid Freezing

How much heat to evaporate?

• Heat of Vaporization: Energy required to make a substance evaporate– Also energy released when condensing

• Heat of Fusion: Energy required to make a substance melt– Also energy released when freezing

Lots of energy to evaporate

• Why we feel cold after being in the pool

End Notes for Quiz 8.1 – 8.3

Objectives

• 8.4 Explain how a gas exerts pressure on its container

• 8.4 State and explain how the pressure of a container of gas is affected when the volume is changed

• 8.4 Explain the relationship between temperature and the volume of gas

Objectives

• 8.5 State Archimedes principle and predict whether an object will sink or float in water

• 8.5 State Pascal's principle and describe the operation of a machine that uses Pascal's principle

• 8.5 State Bernoulli's principle and describe a way that Bernoulli's principle is applied

• Pressure is the amount of force applied to an area.

Pressure

• Measured in Pascals

P = FA

Weight of the Atmosphere

• Varies on a regular basis– High and Low

pressure• Varies by location

– Mountains have less air on top

• less pressure = lower BP

• Some people claim that they can detect these changes… myth or fact?

Pressure

• Increase Temperature: More Pressure

• Increase the amount of molecules: More Pressure

What is the pressure (in PSI)

• On your feet?• On an elephant’s

feet?• On a high heel

shoe?

Boyle’s Law

• Boyle’s Law: A law which relates how volume and pressure of a gas are related

• Pressure goes up, volume goes down

Boyle’s Law Examples

• Pertinent to our breathing. • How big of a pressure difference do you think

our chest cavities can create? – What is the volume of your lungs when fully

inhaled?– What is the volume of your lungs when fully

exhaled?• Explain how a vacuum works

Boyle’s Law Examples

• Relevant to weather balloons• As the balloon rises, the pressure on the

outside decreases, the balloon expands so that the pressure inside is the same as the outside– At approximately 15 km, the altitude is 1/10 of sea

level, so the balloon will expand to a volume of 10x its original

– Balloons pop at certain height

Boyle’s Law Examples

• Relevant to deep sea divers– 10 m of water depth is equal approximately to the

atmosphere– At high pressure, gas is forced into the blood

stream easier. Later on, when you return, the gas in the vessels and arteries expands, called the Benz

Boyle’s Law Examples

• Relevant to medicine– Hyperbaric chambers: High pressure container

designed to help the body heal– Used by sports teams, used to treat premature

babies, used for patients after heart attacks– Some Young Earth Creationists speculate that

before the flood, pressure was larger allowing for large animals to exist

– Used for bigger plants too (super green house)

Charles Law

• Charles Law: A law which relates how volume and temperature of a gas are related

• As Temperature goes up, the volume goes up– Think Hot Air Balloons. More volume = Less

Density

Buoyancy

• Buoyant Force: The ability of a fluid to exert an upward force on an object immersed in it– Based on Densities

dictates how much lift you get

Archimedes Principle

• Archimedes Principle: Buoyant force on an object is equal to the weight of the fluid displaced– If the object has a

weight of 50 g, it will displace 50 g of water (if it floats)

• Only works if you are floating

Pascal’s Principle

• Pascal’s Principle: A principle which states that pressure exerted on a fluid is transferred to another location unchanged through the fluid

Mechanical Advantage

Bernoulli’s Principle

• Bernoulli’s Principle: A principle which relates the velocity of a fluid and the pressure the fluid exerts

Venturi Effect

• Venturi Effect: A special case of Bernoulli’s principle seen in windy cities