chapter 9: heat and states of matter section 1: temperature and thermal energy
TRANSCRIPT
Chapter 9:Heat and States of Matter
Section 1: Temperature and Thermal Energy
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• The motion of the particles in matter is described by KINETIC THEORY of matter.
• Matter is composed of particles that are atoms, molecules, or ions that always are in random motion.
Kinetic Theory of Matter
Temperature and Thermal EnergyTemperature and Thermal Energy
• The TEMPERATURE of a substance is a measure of the average kinetic energy of its particles.
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• The SI unit for temperature is the KELVIN (K).
Temperature
Temperature and Thermal EnergyTemperature and Thermal Energy
11 Temperature
Temperature and Thermal EnergyTemperature and Thermal Energy
• Commonly used temperature scales are the Celsius scale and the Fahrenheit scale.
°C = (5/9)(°F – 32) °F = 1.8 (°C) + 32
Conversion Equations:
11 Temperature
Temperature and Thermal EnergyTemperature and Thermal Energy
°F = 1.8 (°C) + 32°
Using Conversion Equations:
Room temperature is considered to be 22 °CWhat is this temperature in °F?
°F = 1.8 (22°) + 32°
°F = 39.6° + 32°°F = 71.6 °F
11 Temperature
Temperature and Thermal EnergyTemperature and Thermal Energy
°C = (5/9) (°F – 32)
Using Conversion Equations:
Water boils at 212 °F at standard temperature and pressureWhat is this temperature in °C?
°C = (5/9)(212° – 32)
°C = (5/9) (180°)°C = 100°F
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• The sum of the kinetic and potential energies of all the particles in an object is the THERMAL ENERGY of the object.
• The increase in an object’s speed doesn’t affect the random motion of its particles, so it doesn’t affect its thermal energy.
Thermal Energy
Temperature and Thermal EnergyTemperature and Thermal Energy
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• HEAT is thermal energy that flows from something at a higher temperature to something at a lower temperature.
• Heat is a form of energy, so it is measured in joules.
Heat
Temperature and Thermal EnergyTemperature and Thermal Energy
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• The amount of thermal energy needed to raise the temperature of 1 kg of some material by 1°C is called the SPECIFIC HEAT of the material.
• Specific heat is measured in joules per kilogram per degree Celsius.
Specific Heat
Temperature and Thermal EnergyTemperature and Thermal Energy
11 Changes in Thermal Energy
Temperature and Thermal EnergyTemperature and Thermal Energy
Change in Thermal Energy (J) =
mass (Kg) x change in temperature (C) x specific heat ( J/Kg°C)
Q = m (Tf – Ti) C
J = (Kg)(°C ) J Kg °C
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• The specific heat of a material can be measured using a device called a CALORIMETER.
• In a calorimeter, a heated sample transfers thermal energy to a known mass of water.
Measuring Specific Heat
Temperature and Thermal EnergyTemperature and Thermal Energy
11 Measuring Specific Heat
Temperature and Thermal EnergyTemperature and Thermal Energy
• The thermal energy released by the sample is equal to the thermal energy absorbed by the water.
11Section CheckSection Check
Question 1
How is temperature related to kinetic energy?
11Section CheckSection Check
Temperature is a measure of the average kinetic energy of the particles in an object or material. As the temperature increases, the average speed of the particles increases.
Answer
11Section CheckSection Check
Question 2
How does thermal energy differ from kinetic energy?
Answer
Thermal energy is the sum of the kinetic and potential energy of all the particles in an object.
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Question 3
The amount of heat that is needed to raise the temperature of 1 kg of a material by 1º C is called the __________ of the material.
A. densityB. massC. specific heatD. thermal energy
11Section CheckSection Check
Answer
The answer is C. Specific heat is measured in joules/kilogram °C.