# < BackNext >PreviewMain Section 1 Temperature What Is Temperature? Temperature is a measure of the average kinetic energy of the particles in an object.

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< BackNext >PreviewMain Section 1 Temperature What Is Temperature? Temperature is a measure of the average kinetic energy of the particles in an object. Kinetic energy is the energy of motion. All moving objects have kinetic energy. The amount of kinetic energy that an object has depends on the object’s mass and speed. Chapter 10

< BackNext >PreviewMain Section 1 Temperature What Is Temperature?, continued Temperature and Kinetic Energy All matter is made of atoms or molecules that are always moving. The faster the particles are moving, the more kinetic energy they have. The more kinetic energy the particles of an object have, the higher the temperature of the object is. Chapter 10

< BackNext >PreviewMain Section 1 Temperature What Is Temperature?, continued The gas particles on the right have a higher average kinetic energy than those on the left. So, the gas on the right is at a higher temperature. Chapter 10

< BackNext >PreviewMain Section 1 Temperature What Is Temperature?, continued Average Kinetic Energy of Particles The motion of particles in matter is random, so individual particles have different amounts of kinetic energy. When you measure an object’s temperature, you are measuring the average kinetic energy of the particles in the object. Chapter 10

< BackNext >PreviewMain Section 1 Temperature Measuring Temperature Using a Thermometer Thermometers can measure temperature because of a property called thermal expansion. Thermal expansion is the increase in volume of a substance in response to an increase in temperature. As a substance’s temperature increases, its particles move faster and spread out. Chapter 10

< BackNext >PreviewMain Section 1 Temperature Measuring Temperature, continued Temperature Scales Three common temperature scales are the Celsius scale, the Fahrenheit scale, and the Kelvin scale. The Kelvin scale is the official SI temperature scale. The lowest temperature on the Kelvin scale is 0 K, which is called absolute zero. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Transferred Thermal Energy Heat is the energy transferred between objects that are at different temperatures. When two objects at different temperatures come into contact, energy is always transferred from the object that has the higher temperature to the object that has the lower temperature. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Transferred Thermal Energy, continued Heat and Thermal Energy Heat is transferred in the form of thermal energy. Thermal energy is the total kinetic energy of the particles that make up a substance. Thermal energy depends partly on temperature. Thermal energy also depends on how much of a substance there is. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Conduction, Convection, and Radiation Thermal Conduction is the transfer of thermal energy from one substance to another through direct contact. Conduction can also occur within a substance. The particles of substances as different temperatures have different average kinetic energies. When such substances touch, their particles collide. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Conduction, Convection, and Radiation, continued When particles collide, particles with higher kinetic energy transfer energy to those with lower kinetic energy. This transfer of energy happens until all particles have the same average kinetic energy. As a result, the substances have the same temperature. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Conduction, Convection, and Radiation, continued Conductors and Insulators Substances that conduct thermal energy well are called thermal conductors. Most metals are thermal conductors. Substances that do not conduct thermal energy well are called thermal insulators. Wood and plastic are examples of thermal insulators. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Conduction, Convection, and Radiation, continued Convection is the transfer of thermal energy by the movement of a liquid or a gas. As water is heated, it becomes less dense. The warmer water rises through the cooler water above it. At the surface, the warm water cools and becomes more dense. The cooler water then sinks to the bottom and the cycle repeats. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Conduction, Convection, and Radiation, continued Radiation is the transfer of energy by electromagnetic (EM) waves. All objects radiate EM waves. Unlike conduction and convection, radiation can involve either a transfer of energy between particles of matter or an energy transfer across empty space. Chapter 10

< BackNext >PreviewMain Section 2 What Is Heat? Heat and Temperature Change Thermal Conductivity is the rate at which a substance conducts thermal energy. Because of its high thermal conductivity, metal transfers energy more rapidly than cloth does. If a piece of metal and a piece of cloth are left in sunlight and are at the same high temperature, the metal will feel hotter when touched. Chapter 10

< BackNext >PreviewMain Section 3 Matter and Heat States of Matter The states of matter are the physical forms in which a substance can exist. Three familiar states of matter are solid, liquid, and gas. The state a substance is in depends on the speed of its particles, the attraction between them, and the pressure around them. Chapter 10

< BackNext >PreviewMain Section 3 Matter and Heat Changes of State A change of state is a change of a substance from one state of matter to another. Changes of state include freezing (liquid to a solid), melting (solid to liquid), boiling (liquid to gas), and condensing (gas to liquid). Chapter 10

< BackNext >PreviewMain Section 3 Matter and Heat Changes of State, continued Chapter 10

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