Physics II

PHY 202/222

Temp, Heat & Gas Laws

452 South Anderson Road Rock Hill, SC 29730 www.yorktech.com

Temp, Heat & Gas Laws Test 2

Beiser Chapters 18, 19 & 22 - Multiple Choice – Odd - Supplementary Problems - Odd Browne Chapter 17 for PHY 221 Students - Supplementary Problems - 4,5,10,14

Beiser Chapter 18 - Heat

Beiser p.213

Stuff

Remember: All matter is composed of molecules which are moving rapidly. Since these molecules are moving and have mass, they have kinetic energy!

Beiser p.213

Definitions • Internal Energy – sum of the kinetic energies of molecules of matter • Temperature – measure of average kinetic energy of molecules • Heat – internal energy in transit • Thermometer – a device to measure temperature Beiser p.213-4

Water freezes Water boils 100 o C Temperature Scales

Celsius Kelvin (Celsius +273) Fahrenheit

0 o C 273 K 32 o F T 373 K 212 o F T F  9 5 T C  32 T C  5 9 (T F  32) Beiser p.214

Heat (Internal energy in transit) Units of heat • Joule - SI unit • Calorie (cal) - heat needed to raise 1 g of water 1 o C • Kilocalorie (kcal) – heat needed to raise 1 kg of water 1 o C (same as calorie in food info) • 1 kcal = 1000 cal Q Beiser p.214

Heat “British” Units of heat • British Thermal Units (BTU) – heat needed to raise 1 lb of water 1 o F • 1 kcal = 3.97 BTU = 4185 J Q Beiser p.214

Iron Water Ice Specific Heat Capacity Wood J/(kg o C) 4187 2090 1700 1.00

0.5

0.4

C How much energy does it take to change the temperature of the material.

Aluminum Glass 900 840 cal/(g o C) or kcal/(kg o C) 0.215

0.200

448 0.107

Copper 390 0.0920

Beiser p.214

Change of State Beiser p.216-7

Calorimetry

• Sensible heat – adding heat raises temperature Q  • Latent heat – adding heat changes state Q  m L Beiser p.215-7

Calorimetry example

• How much heat will it take to melt 2 kg of ice?

Q  m L f  2kg(335 kJ / kg)  670 kJ 670 kJ • How much heat will it take to raise the temperature of 2 kg of water by 17 o Q  C?

 o o  • How much heat will it take to melt 2 kg of ice and raise the temperature to 17 o C?

Q Total   812 kJ Beiser p.215

142 kJ

Mixing problem

Add 200 g of iron at 100 o C to 600 g of water at 20 o C. Find the final temperature.

Heat gained by water = Heat lost by bar m water c water  T water  m c bar bar  T bar (.6 kg)(4.185

kJ o kg C )(T  o 20 C)  (.2 kg)(.448

kJ o kg C  2.56 T  o 59.18 C T  o 23.1 C o  Beiser p.216

18.4

18.6

18.8

18.10

18.12

18.14

18.16

18.18

18.20

18.22

18.24

Beiser Chapter 19 Thermal Expansion Beiser p.224

Linear Expansion

a L O  T L O ΔL ΔT Beiser p.224

Volume Expansion

b V O  T V O V = V O + ΔV ΔT Beiser p.224

Boyle’s Law

p V 1 1  p V 2 2 when T is constant V 1 P 1 ΔT= 0 V 2 P 2 As volume goes up, pressure goes down to keep the product constant.

Beiser p.226

V 1 T 1

Charles’s Law

V 1 T 1  V 2 T 2 when p is constant Δp = 0 V 2 T 2 As volume goes up, temperature drops.

T must be in K!

Beiser p.227

The Ideal Gas Law

p V 1 1 T 1  p V 2 2 T 2 V P T 1 1 1 V 2 P 2 T 2 Volume, pressure and temperature are all related by the Ideal Gas Law.

Beiser p.228

19.2

19.4

19.6

19.8

19.14

19.16

Chapter 22 Heat Transfer Beiser p.259

Rate of Heat Conduction

Heating by contact/collisions between molecules.

Q  t d Q heat t time k thermal conductivity - look up A cross section area ΔT ΔT from 1 hot to cold side d length/thickness of material Beiser p.259

Thermal Resistance

R k thickness thermal conductivity

Material

Air Wood Water Glass Iron Aluminum Copper Silver

k (W/m o C)

.026

0.12

0.61

0.8

80.3

237 398 427 Beiser p.260

Convection

Heating by motion of a hot fluid.

Q  t Q heat t time h factor will be given A area of contact hot to fluid ΔT ΔT between hot and fluid Beiser p.261

Radiation

Heating by energy from electro-magnetic waves.

Stefan-Boltzmann Law R  P A 4 R rate of radiation P power emitted A surface area T temperature σ = 5.67 E-8 W/(m 2 K 4 ) e emissivity 0 total reflection 1 blackbody/total absorption 0

22.4

22.6

22.10