Chapter-10 Temperature and Heat



Download 7,89 Kb.
Date conversion11.09.2018
Size7,89 Kb.

Chapter-10 Temperature and Heat

  • 1 Temperature and First Law of Thermodynamics
  • Heat and Specific Heat Capacity
  • First Law of Thermodynamics
  • Ideal Gas law
  • The Flow of Heat
  • Essay Topic for Final: Global Warming

Body Temperature

  • Thermometer
  • Thermometric Property
  • Constant-volume gas thermometer
  • Pressure of the gas
  • Thermocouple
  • Voltage
  • Ear thermometer
  • Infrared radiation

The zeroth Law of Thermodynamics

  • If system A is in thermal equilibrium with system T and system B is in thermal equilibrium with system T, then systems A and B are in thermal equilibrium with each other.

Thermometer

  • Standard Temperatures
  • Calibration

Temperature Conversion

  •  
  • Fahrenheit scale
  • Celsius scale
  • 212
  • 100
  •  
  •  
  • Unknown temperature
  •  
  •  
  •  
  • Tf
  •  
  •  
  • Tc
  •  
  •  
  • Freezing point of water
  • 32
  • 0

Absolute Zero Temperature

Temp. Conversion Problems E1 & E4

  • E1: An object has a temperature of 45°C. What is its temperature in °F?
  • E4: The temperature on a warm summer day is 95 degrees F. What is this temperature a. In degrees Celsius?
  • b. In Kelvin?

Heat

  • Heat is energy that flows from a higher-temperature object to a lower-temperature object because of the difference in temperatures.

Units for Heat

  • SI unit for heat is the joule, J.
  • Calorie is another unit for heat. It comes with a lower case and an upper case.
  • Nutritionists use the word “Calorie,” with a capital C, to specify the energy content of foods. For example, a regular 12-oz can of soda has about 140 Calories.
  • The cgs unit of heat is the calorie, with a lower case. One calorie (1 cal) is defined as the amount of heat needed to raise the temperature of one gram of water by one Celsius degree.
  • 1 food Calorie = 1000 calories = 1 kcal
  • 1 calorie = 4.186 J.

Specific Heat Capacity

  • Specific heat capacity of a material is the quantity of heat needed to change a unit mass of the material by a unit change in temperature. It is a property of the material.
  • Specific Heat Capacities of Some Common Substances
  • Substance
  • Specific heat capacity [cal/(g. C°)]
  • Water
  • 1.0
  • Ice
  • 0.49
  • Steam
  • 0.48
  • Ethyl alcohol
  • 0.58
  • Steel
  • 0.11
  • Aluminum
  • 0.215
  • Lead
  • 0.0305

Heat Q

  • The heat Q that must be supplied or removed to change the temperature of a substance of mass m by an amount T is,
  • where c is the specific heat capacity of the substance.
  • Unit for Specific Heat Capacity:
  • SI: J/(kg · C°)
  • cgs: cal/(g. C°)
  • E6: How much heat is required to raise the temperature of 70 g of water from 20°C to 80°C?

Calorimetry

  • SP4: A 150-g of a certain metal, initially at 120°C, is dropped into an insulated beaker containing 100 g of water at 20°C. The final temperature of the system is 35°C.
  • Ignore the heat capacity of the beaker.
  • How much heat has been transferred to the water from the metal?
  • What is the specific heat capacity of the metal?

Phase Changes: Latent Heat

  • Latent heat changes the phase of water without changing its temperature.
  • Latent heat of fusion of water = Lf = 80 cal/g.
  • Latent heat of vaporization of water = Lv = 540 cal/g.
  • E8: How much heat must be added to 60-g of ice at 0°C to melt completely?

The First Law of Thermodynamics

  • ΔU = Q - W

Ideal Gas Law

  • PV =NkT

The Flow of Heat

  • Heat can flow via conduction, convection, and radiation.

Conduction and Convection

  • When a metal block and a wooden block, both at room temperature, are picked up, the metal block feels cooler, due to conduction of heat.
  • Conduction is the process whereby heat is transferred directly through a material.
  • Convection is the process in which heat is carried from place to place by the bulk movement of a fluid.

Radiation

  • Radiation is the process in which energy is transferred by means of electromagnetic waves.
  • Heat transfer by radiation can take place through vacuum.
  • This is because electromagnetic waves are involved in radiation and they can propagate through empty space.
  • Thermos Bottle
  • Q30: Which heat transfer process is responsible when heat flows through a glass windowpane?


The database is protected by copyright ©sckool.org 2016
send message

    Main page