# Chapter-10 Temperature and Heat

 Date conversion 11.09.2018 Size 7,89 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

## 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

## 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?

• ΔU = Q - W

• 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.