Chapter 13

Chapter 13

States of Matter

13.1- Properties of Fluids

• Fluids- liquids and gases; materials that flow and have no definite shapes of their own

*For now imagine these are ideal– Particles take up no space– Particles have no intermolecular attractive forces

Pressure in Fluids

• Pressure- the force on a surface divided by the area of the surface

• P=F/A

• Anything that exerts pressure is capable of producing change and doing work.

• Pascal (Pa)- 1N/m2

Solids, Liquids, and Pressure

Gas Particles and Pressure

Atmospheric Pressure

• On every square centimenter of Earth’s surface at sea level, the atmospheric gas exerts a force of approximately 10 N, about the weight of a 1 kg object.

• Why don’t we “feel” this pressure?

• When might we “feel” this pressure?

The Gas Laws

• Boyle’s Law- P1V1=P2V2

(Pressure must be in kPa)

• Charles’s Law- V1/T1=V2/T2

(Volume must be in Liters)• Combined Gas Law- P1V1/T1=P2V2/T2

(Temperature must be in Kelvins)• Ideal Gas Law- PV=nRT

Ideal Gas Law

• PV=nRT– P is pressure in _______________– V is volume in _______________– n= number of moles of the substance

• 1 mole= _______________ particles (Avagadro’s Number)

– R= 8.31 Pa m3/mol K– T= temperature in _______________

Does not work well with high pressures or low temperatures

• The pressure on a can of soda is 375 kPa and the volume is 20.8 L. What would the new volume be if the pressure increased to 480 kPa?

• Do pressure and volume have a direct or inverse relationship?

• If a Balloon has a volume of 20.0 L at a temperature of 27.2 oC what will be the new volume if the temperature decreases to 0.00 oC?

• Do volume and temperature have a direct or inverse relationship?

Thermal Expansion

• Hot items become less dense and fill up more space- They will _______________

• Cold items become more dense and take up less space- They will _______________

Plasma

• Gas-like state of negatively charged and positively charged ions– Found in stars, lightning, and neon signs

13.2- Forces within Liquid

• Surface Tension- tendency of the surface of a liquid to contract to the smallest possible area

• Cohesive Forces- attraction between like molecules

Viscosity

• Ability to resist flow

Maple syrup vs Kool-Aid

Water vs Honey

Rubbing Alcohol vs Ketchup

Adhesive Forces

• Electromagnetic attractive forces that act between particles of different substances

• Capillary Action- liquid rising due to adhesive forces– Water in Tube– Wax on Wick of Candle– Water in Soil and Roots

Evaporation and Condensation

• Evaporation- escape of the most energetic particles of a liquid to a gas; Leaves liquid with less KE so temperature will _______________.

• Condensation- loss of energy causing particles of gas to convert to liquid

Isopropyl ( ) Methyl( ) Ethyl( )

+ Δ

• Easy to follow• Fun!• Hands On• Visualize what we talk

about in class!

• Go over more questions together

• Some questions are confusing

• Long questions• Goggles

13.3- Fluids at Rest and in Motion

• Pascal’s Prinicple- any change in pressure applied at any point on a confined fluid is transmitted undiminished throughout a fluid– Example: Squeezing a tube of toothpaste

• F1A1=F2A2

• Pascal's Principle

Swimming Under Pressure

• The pressure of the water is equal to the weight of the water directly above the object divided by the cross sectional area of the column above the object

• P=Fg/A• Density=mass/volume• Volume=length x width x height• Area=length x width• Force=mass x acceleration

Use these formulas to derive P=phg from P=Fg/A

(5 minutes: YOU CAN DO IT!!!)

• P=F/A• P=ma/A• P=ρVg/A• P=ρhAg/A• P=ρhg

The pressure that a column of water exerts on a body is equal to the density of water times the height of the column times the acceleration due to gravity.

Buoyancy

• Archimedes Principle and Buoyant Force

• Buoyant force- the increase in pressure with increasing depth creates this upward force

• To see if an object will float compare downward force to upward force– Ptop=Ftop/Atop=ρhgA

– Pbottom=Fbottom/Abottom=ρ(l+h)gA

– Fbuoyant=Fbottom-Ftop=ρlga=ρfluidVg

Fbuoyant=Fbottom-Ftop=ρlga=ρfluidVg

• The buoyant force on an object is equal to the weight of the fluid displaced by the object, which is equal to the density of the fluid in which the object is immersed multiplied by the object’s volume and the acceleration due to gravity.

Archimedes' Principle

• An object immersed in a fluid has an upward force on it that is equal to the weight of the fluid displaced by the object.

Sink or Float?

• All objects in a liquid, even those that sink, have an apparent weight that is less than when the object is in air.

• Fapparent= Fg- Fbuoyant