Slide 1 / 105 Slide 2 / 105 Topics to be covered Thermal Physics Temperature and Thermal Equilibrium Kinetic Theory Gas Laws Internal Energy Heat Work Laws of Thermodynamics Heat Engines Slide 3 / 105 Slide 4 / 105 Temperature Thermodynamics System The concept of temperature is rooted in qualitative Originally, in 1824 Sadi Carnot describe a ideas of "hot" and "cold" based on our sense of thermodynamics system as the working touch. An object that feels hot has a higher substance under study. temperature than a similar object that feels cold. Measuring temperature based on our sense is In Thermodynamics - system is any region very subjective. When we touch different objects completely enclosed within a well defined in our classroom we will find that metallic objects boundary. Everything outside the system is feel cooler than wooden or plastic objects which then defined as surroundings. is not true because they have all been in the same Very often in this chapter we will use a word room for a long time. They all have the same "system" instead of cylinder of gas, container temperature. filled with water, ice cube. Slide 5 / 105 Slide 6 / 105 Temperature Temperature Thermometers are instruments designed to measure temperature. There is a better way of measuring temperature based on properties of matter that depend on temperature. The volume of liquid, length of a metal rod, gas pressure, electroconductivity, and the color of a hot glowing object.
Slide 7 / 105 Slide 8 / 105 Temperature Temperature In everyday life, we use liquid-in-tube thermometers The relationships among three different temperature scale are presented by the table below. which are based on thermal expansion of liquids. In addition to thermometers we need some kind of a common scale that we can use to present different temperatures. In Europe, the most common is Celsius scale. In the United State, the most common is Fahrenheit scale. In science, the most important is Absolute or Kelvin scale. Slide 9 / 105 Slide 10 / 105 1 Which temperature scale never gives negative temperatures? Temperature A Fahrenheit The following formulas we can use to convert temperature B Kelvin from one scale to another. C Celsius D Reaumur E All of the above Slide 11 / 105 Slide 12 / 105 2 Freezing point of water is 32 ̊F; what is this on Celsius scale? 3 “Room temperature” is often taken to be 68 ̊F; what is this on the Celsius scale? A 32 A 25 B 0 B 45 273 C C 34 212 D D 20 E 25 E 15
Slide 13 / 105 Slide 14 / 105 4 The temperature of a human body is 37 ̊C; what is this on 5 The temperature of boiling water is 100 ̊C; what is this on the Fahrenheit scale? the Fahrenheit scale? A 25.9 A 0 B 60.5 B 32 C 78.2 C 100 D 98.6 D 273 E 42.8 E 212 Slide 15 / 105 Slide 16 / 105 6 Melting point of ice is 0 ̊C; what is this on the Kelvin scale? 7 Absolute zero is what temperature on the Celsius scale? A 0 A 0 B 32 B 273 C 373 C -32 D 273 D -273 E 212 E 32 Slide 17 / 105 Slide 18 / 105 8 Three objects A, B, and C initially have different temperatures T A >T B >T C . Objects A and B are Thermal Equilibrium and the Zeroth Law separated by an insulating plate but they are in contact with object C through a conducting of Thermodynamics platform. Which of the following is true when objects A and B reach thermal equilibrium with Two objects placed in thermal contact will eventually object C? come to the same temperature. When they do, we say A The temperature of all three objects stays unchanged they are in thermal equilibrium. B Object A has higher temperature than object B and C The zeroth law of thermodynamics says that if two C Object C has higher temperature that object A and B objects are each in equilibrium with a third object, they D Object B has higher temperature that object A and C are also in thermal equilibrium with each other. E All three objects have the same temperature
Slide 19 / 105 Slide 20 / 105 9 A simple pendulum is made of a steel string supporting a brass sphere. The temprerature in a room with the pendulum is increased from 15 C to 30 C. Which of the folowing is true about the period of oscillations? A The period is doubled B The period stays unchanged C The period is increased by # 2 The period is decreased by # 2 D E The period is slightly increased Slide 21 / 105 Slide 22 / 105 10 A glass flask is filled with glycerin up to the top. When the Thermal Expansion temperature of surroundings is increased by a few degrees, which Volume thermal expansion occurs when increasing of the following is true about the level of glycerin in the flask? (The coefficients of volume expansion are: # glycerin =49x10 -5 K -1 , temperature causes increases in volume for both solid # glass = 2x10 -5 K -1 ) and liquid materials. A The level of glycerin in the flask goes down The level of glycerin stays unchanged B because the both expand Where # is the coefficient of volume expansion. C Glycerin spills out of the flask It can't be determined from the given D information Slide 23 / 105 Slide 24 / 105 Thermal Expansion Kinetic Theory Water, in the temperature range from 0 o C to 4 o C, decreases in its volume and increases in density. Above 4 o C, water expands when Many properties of matter such as: thermal expansion, heated. Hence water has its greatest density at 4 o C. Water also melting, boiling, cooling, heating... can be explained based expands when it freezes, which is why a piece of ice floats on water on the concept that matter is made up of tiny particles. surface.
Slide 25 / 105 Slide 26 / 105 Kinetic Theory Kinetic Theory Kinetic Theory studies the macroscopic properties of The idea that all familiar matter is made up of atoms goes matter in terms of its atomic structure and behavior. This back to the ancient Greeks. According to them if we were theory has a tremendous practical importance; once we cut a piece of iron into smaller and smaller portions, have this understanding , we can design materials with eventually a smallest piece of iron would be obtained specific desired properties. which could not be divided further. This smallest piece is The analysis to this theory has led to development of high- called an atom (indivisible). strength steels, glasses with special optical properties, semiconductors. Slide 27 / 105 Slide 28 / 105 Kinetic Theory Kinetic Theory The assumptions of ideal gas model are: The study of a real gas is very complicated from 1. A container contains a very large number of particles mathematical point of view. In our discussion of the (atoms, molecules). kinetic theory we will be using a simplified mathematical model which is called - ideal gas. 2. The atoms behave as point particles; their size is small in comparison to the average distance between particles and to the size of the container. 3. The particles are in constant motion; they obey Newton's Laws of motion. Each particle collides occasionally with a wall of the container. These collisions are perfectly elastic. 4. The walls of the container are rigid and very massive. Slide 29 / 105 Slide 30 / 105 Kinetic Theory 11 Which of the following is not included into the assumptions of the Now we will calculate the pressure in the ideal gas ideal gas? based on kinetic theory. First we will find the change in momentum during one single collision of a molecule A The number of molecules in a container is very large with a wall of the container. B The molecules interact when they collide with each other The change in momentum in the The molecules interact all the time during their motion because C direction perpendicular to the of intermolecular forces wall is: D The collisions between molecules are perfectly elastic E The size of molecules can be ignored Assuming that the collision is perfectly elastic and
Slide 31 / 105 Slide 32 / 105 Kinetic Theory Kinetic Theory The time between the collisions is If a molecule is going to collide with very small, so the number of a given wall area A during a small collisions per second is very large. time interval # t, which is the time it According to Newton's Laws the average force will be equal to the takes the molecule to travel across force exerted during one collision the box and back again, a distance equal to 2L. Where 2L = v x # t. divided by the time between the collisions. Slide 33 / 105 Slide 34 / 105 Kinetic Theory Kinetic Theory To calculate the force due to The force due to all molecules is all the molecules in the box, we have to add the contributions of each. From Pythegorian Theorem: Since all molecules move in random directions and The average value of the square of the x component there is no preference between x, y, and z we can of velocity is write the following: or Slide 35 / 105 Slide 36 / 105 Kinetic Theory Kinetic Theory The last equation can be modified by replacing average velocity with the average kinetic energy Now we can change the square of of molecules. the velocity component to the square of the velocity. The pressure on the wall is It was found from the series of experiments that force per unit of area. which is called the ideal-gas equation. Where k= 1.38x10 -23 J/K is Boltzmann's constant. or
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