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What are temperature and heat?
Are they the same?
What causes heat?
How do we measure
temperature?What are we
actually measuring?
Temperature and Its MeasurementHow do we measure temperature?Thermometer: Device with a physical
property that changes with temperature and can be easily measured quantitatively.
If two objects are in contact with one another long enough, the two objects have the same temperature (thermal equilibrium).
Two or more objects in thermal equilibrium have the same temperature.
Zeroth law of thermodynamics.
Temperature Scales
The first widely used temperature scale was devised by Gabriel Fahrenheit.
Water freezing point: 32FWater boiling point: 212F
Another widely used scale was devised by Anders Celsius.
Water freezing point: 0C.Water boiling point: 100C
Temperature Scales
Conversion between two scales:
E1. An object has a temperature of 45C. What is its temperature in degree Fahrenheit?
E2. The temperature of a winter day is 14F. What is the temperature in degree Celsius?
TC 59
TF 32
TF 95
TC 32
Zero TemperatureThe zero point on the
Fahrenheit scale was based on the temperature of a mixture of salt and ice in a saturated salt solution.
The zero point on the Celsius scale is the freezing point of water.
Both scales go below zero.Is there an absolute
zero?
What is absolute zero?If the volume of a gas is kept
constant while the temperature is different, the pressure will be different.
The Third Temperature Scale
Absolute Temperature Scale (Kelvin Scale)
ExampleWater freezing point: 0C =273.2 K.Water boiling point: 100C = 373.2 K
TK TC 273.2
Heat and TemperatureHeat:
Heat is the energy that flows from one object to another when there is a difference in temperature between the objects. Heat is the average kinetic energy of atoms or molecules making up the system.
Temperature: Temperature is an indication of whether or not and in which direction, the heat will flow (Temperature is an indication of the average of kinetic energy of atoms or molecules).
The Flow of Heat
Three basic processes for heat flow:ConductionConvectionRadiation
A metal block at room temperature will feel colder than a wood block of the exact same temperature. Why?
The rate of heat flow depends on: a) the temperature difference between the objects.b) the thermal conductivity of the materials, a measure of how well the materials conduct heat.
Conduction: heat flow when in contact
Convection: heat is transferred by the motion of a fluid containing thermal energy.
Radiation, heat energy is transferred by electromagnetic waves. can take place across a vacuum.
What heat-flow processes are involved in the greenhouse effect?
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