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Chapter # 12 Section 12.1. Temperature, Heat and Thermal Energy. Learning Objectives. How are temperature and thermal energy related? How is thermal energy transferred? Describe the system and its surroundings. Identify, in terms of energy transfer, whether the system is open or closed.
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Chapter # 12 Section 12.1 Temperature, Heat and Thermal Energy
Learning Objectives • How are temperature and thermal energy related? • How is thermal energy transferred? • Describe the system and its surroundings. • Identify, in terms of energy transfer, whether the system is open or closed.
SECTION12.1 Heat and Thermal Energy Heatis a transfer of thermal energy that occurs spontaneously from a warmer object to a cooler object. • Thermal energy is related to the motion of an object’s particles and can be transferred and transformed.
Transfer of thermal Energy Example balloon • When you fill up a balloon with helium, the rubber in the balloon is stretched by the repeated pounding from helium atoms. • Gas atoms collide with the rubber wall, bounces back, and hits the other side of the balloon wall.
If you put a balloon in sunlight, the balloon gets slightly larger. • Reason: • Each atomic collision with the balloon wall puts a greater force on the balloon and stretches the rubber. • Thus, the balloon expands.
if you refrigerate a balloon, you will find that it shrinks slightly. • Reason: • Lowering the temperature slows the movement of the helium atoms.
Conclusion • A hot object has more thermal energy than a similar cold object. • Thermal Energy Transfer of heat from Hot place to cold place.
Temperature • Temperature depends only on the average kinetic energy of the particles in the object.
What happens to the surroundings? The surroundings gain heat energy 0r get hotter?
Example: Temperature • Consider two blocks of steel. The first block has a mass of 1 kg, and the second block has a mass of 2 kg. • If the 1-kg block is at the same temperature as the 2-kg block, the average kinetic energy of the particles in each block is the same.
What is a system? • A system is the part of the universe that we are studying. • For example the cup.
What are the surroundings? • EVERYTHINGELSEINTHEUNIVERSE!!
Energy transfer is studied in three types of systems: 1-Open System 2-Closed System 3-Isolated System
Open systems • Open systems can exchange both matter and energy with an outside system. They are portions of larger systems and in intimate contact with the larger system. Your body is an open system.
Closed systems • Closed systems exchange energy but not matter with an outside system. • Example: The Earth is essentially a closed stem; it obtains lots of energy from the Sun but the exchange of matter with the outside is almost zero.
Isolated systems • Isolated systems can exchange neither energy nor matter with an outside system. • a closed thermos bottle is essentially an isolated
A cup of ice • Identify the system and its surroundings. • Predict the direction of the energy transfer. • Identify, in terms of energy transfer, whether the system is open or closed. • Define a new system by changing the boundary of the system, and define whether the new system is open or closed.
A cup of hot chocolate • Identify a system and its surroundings. • Predict the direction of the energy transfer. • Identify, in terms of energy transfer, whether the system is open or closed. • Define a new system by changing the boundary of the system, and define whether the new system is open or closed • .
Thermal Equilibrium • Thermal Equilibrium is the state in which the rate of energy flow between two objects is equal and the objects are at the same temperature.
Temperature CHAPTER12 Chapter Resources Thermometers
Temperature, Heat and Thermal Energy SECTION12.1 Equilibrium and Thermometers (cont.) • If an ideal gas, such as helium in a balloon is cooled, it contracts in such a way that it occupies a volume that is only the size of the helium atoms at –273.15°C. • At this temperature, all the thermal energy that can be removed has been removed from the gas. • It is impossible to reduce the temperature any further. • Therefore, there can be no temperature lower than–273.15°C, which is called absolute zero.
Temperature, Heat and Thermal Energy SECTION12.1 Thermometers (cont.) • The solution to this issue is to use a temperature scale based on absolute zero. • The zero point of the Kelvin scale is defined to be absolute zero.
Temperature, Heat and Thermal Energy SECTION12.1 Equilibrium and Thermometers (cont.) • The figure shows representative temperatures on the three most-common scales: Fahrenheit, Celsius, and Kelvin. • Very cold temperatures are reached by liquefying gases.
Temperature, Heat and Thermal Energy SECTION12.1 Equilibrium and Thermometers (cont.) • On the Kelvin scale, the freezing point of water (0°C) is about 273 K and the boiling point of water is about 373 K. • Each interval on this scale, called a kelvin, is equal to 1°C. • Thus, TC + 273 = TK.
