Chapter 1.4 Notes Temperature

An object in motion is capable of doing work and contains energy. An object in motion is capable of doing work and contains energy. The random motion of vibration of an object’s atoms and molecules is called thermal motion. The random motion of vibration of an object’s atoms and molecules is called thermal motion.thermal motionthermal motion The total energy of the thermal motion of all particles that make up an object is called the thermal energy of the object. The total energy of the thermal motion of all particles that make up an object is called the thermal energy of the object.

Whenever two bodies are brought together, thermal energy flows from the hotter body to the colder body. Whenever two bodies are brought together, thermal energy flows from the hotter body to the colder body. The hotness of the body is called temperature. The hotness of the body is called temperature. Temperature is determined by the average kinetic energy of the random motion of the atoms and molecules in a body. Temperature is determined by the average kinetic energy of the random motion of the atoms and molecules in a body.

Thermal energy is measured in joules. Thermal energy is measured in joules. Temperature is measured in degrees. Temperature is measured in degrees.

Most materials expand when their temperatures increase and contract when temperature decreases. expand

A thermometer uses expansion and contraction of a liquid to measure temperature. The liquid is contained in a glass tube and when the thermometer is placed in contact with an object the faster-moving molecules in the water collide with the glass tube. A thermometer uses expansion and contraction of a liquid to measure temperature. The liquid is contained in a glass tube and when the thermometer is placed in contact with an object the faster-moving molecules in the water collide with the glass tube. When the thermal energy between the liquid and the thermometer are equal, the thermometer and liquid are at thermal equilibrium. When the thermal energy between the liquid and the thermometer are equal, the thermometer and liquid are at thermal equilibrium.

In some cases in the U.S., the Fahrenheit scale is still used. Thirty two degrees Fahrenheit is the Freezing point of water and 212 is the boiling point.

The Celsius scale is based on properties of water. Zero degrees Celsius is defined as the freezing point of water at sea level. One hundred degrees Celsius is defined as the boiling point.

To convert from Celsius to Fahrenheit use this equation: To convert from Celsius to Fahrenheit use this equation:convert T C = 5/9 (T F – 32) T C = 5/9 (T F – 32) To convert from Fahrenheit to Celsius use this equation: To convert from Fahrenheit to Celsius use this equation: T F = (9/5T C ) + 32 T F = (9/5T C ) + 32

Convert 50 degrees Fahrenheit to Celsius. Convert 50 degrees Fahrenheit to Celsius. T C = 5/9 (T F – 32) T C = 5/9 (T F – 32) T C = 5/9 (50 – 32) T C = 5/9 (50 – 32) Parenthesis first! Parenthesis first! T C = 5/9 (18) T C = 5/9 (18) T C =.56(18) T C =.56(18) T C = 10 T C = 10

Convert 20 degrees Celsius to Fahrenheit. Convert 20 degrees Celsius to Fahrenheit. T F = (9/5T C ) + 32 T F = (9/5T C ) + 32 T F = (9/5 x 20) + 32 T F = (9/5 x 20) + 32 Parenthesis First! Parenthesis First! T F = (1.8 x 20) + 32 T F = (1.8 x 20) + 32 T F = T F = T F = 68 T F = 68

When thermal energy flows from a hotter object to the cooler object, this is called conduction. When thermal energy flows from a hotter object to the cooler object, this is called conduction.conduction Heat is the energy that flows from one object to another because of a temperature difference. Heat is the energy that flows from one object to another because of a temperature difference. Heat Temperature Difference is the prime mover in thermal systems. Temperature Difference is the prime mover in thermal systems.

In metrics, the unit of thermal energy is the joule. Another commonly used unit is the Calorie In metrics, the unit of thermal energy is the joule. Another commonly used unit is the Calorie 1 cal = Joules 1 cal = Joules One calorie is the amount of thermal energy that must be added to water to change the temperature of 1 gram of water by 1 Degree Celsius. One calorie is the amount of thermal energy that must be added to water to change the temperature of 1 gram of water by 1 Degree Celsius.

The specific heat of a substance is the amount of energy that must be added to raise the temperature of a unit mass of the substance one temperature unit. The specific heat of a substance is the amount of energy that must be added to raise the temperature of a unit mass of the substance one temperature unit.specific heat specific heat The specific heat of water is 1 cal / gC 0 The specific heat of water is 1 cal / gC 0

The specific heat of a substance is represented by C. The specific heat of a substance is represented by C. The amount of heat transferred to an object is represented by the letter Q. The amount of heat transferred to an object is represented by the letter Q. Heat = mass x specific heat x Change in Temperature Heat = mass x specific heat x Change in Temperature Q = m x C x  T Q = m x C x  T

What is the amount of heat transferred when a 500 g mass of water is heated from 20 degrees Celsius to 100 degrees Celsius? What is the amount of heat transferred when a 500 g mass of water is heated from 20 degrees Celsius to 100 degrees Celsius? Q = m x C x  T Q = m x C x  T Q = 500 x 1 x (100 – 20) Q = 500 x 1 x (100 – 20) Q = 500 x 1 x (80) Q = 500 x 1 x (80) Q = 40,000 calories Q = 40,000 calories

When ice reaches 0 degrees Celsius it begins to change state. This is called the melting point. When ice reaches 0 degrees Celsius it begins to change state. This is called the melting point.melting pointmelting point When water reaches 100 degrees Celsius it again changes state. This is the boiling point. When water reaches 100 degrees Celsius it again changes state. This is the boiling point.

The amount of energy required to melt one gram of a solid substance is called the heat of fusion of the substance. The amount of energy required to melt one gram of a solid substance is called the heat of fusion of the substance. heat of fusion heat of fusion The amount of energy required to vaporize one gram of a liquid is called the heat of vaporization The amount of energy required to vaporize one gram of a liquid is called the heat of vaporization

Heat of fusion is represented by H F Heat of fusion is represented by H F Heat of vaporization is represented by H V Heat of vaporization is represented by H V Q (amount of heat needed to melt a solid) = mass x H F Q (amount of heat needed to melt a solid) = mass x H F Q (amount of heat needed to vaporize a liquid) = mass x H V Q (amount of heat needed to vaporize a liquid) = mass x H V

How much energy is needed to melt a 10 gram ice cube? (pg 75) How much energy is needed to melt a 10 gram ice cube? (pg 75) Q = mass x H F Q = mass x H F Heat of fusion of ice? Heat of fusion of ice? Q = 10 x 79.8 Q = 10 x 79.8 Q = 798 cal Q = 798 cal

How much energy is needed to vaporize 10 grams of water? How much energy is needed to vaporize 10 grams of water? Q = mass x H V Q = mass x H V H V of water? H V of water? Q = 10 x 540 Q = 10 x 540 Q = 5400 Q = 5400