1 1 Temperature and Thermal Energy Temperature and energy Glencoe: Chapter 9 – Section 1: pages

1 1 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 Energy

The temperature of a substance is a measure of the average kinetic energy of its particles. 1 1 The SI unit for temperature is the Kelvin (K). As kinetic energy increases the temperature increases Temperature Temperature and Thermal Energy

1 1 Here is a picture showing the three temperature scales side by side

1 1 Temperature Temperature and Thermal Energy B. Thermometer – device that measures temperature  Relies on expansion of heated materials and contraction of cooled materials

1 1 Temperature Temperature and Thermal Energy 1.Liquid thermometers – glass tube filled with a liquid  Limited temperature range a. Mercury filled b. Alcohol filled  Particles move faster as heated and expand and rise up the tube

1 1 Temperature Temperature and Thermal Energy 2. Metal thermometers  2 bonded strips of metal (2 different metals) that expand and contract at different rates  A coiled piece of metal

1 1 Temperature Temperature and Thermal Energy Commonly used temperature scales are the Celsius ( o C) scale, the Fahrenheit ( o F) scale, and the Kelvin (K) scale.

1 1 Temperature Temperature and Thermal Energy Energy Transfer (heat and temperature) - A sense of touch is very important for determining temperature - If the temperature of an object is lower than skin temperature = cold material (ice)  Energy is transferred from the warmer material (skin) to the cooler material as the object’s particles collide with the skin particles

1 1 Temperature Temperature and Thermal Energy If the temperature of an object is higher than skin temperature = warm material (hot water bottle)  Energy is transferred from the warmer material to the cooler material (skin) as the object’s particles collide with the skin particles

1 1 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 Energy

1 1 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. The flow of energy always flows from higher energy (hot) to lower energy ** Warmer will try to “heat up” the cooler** Heat Temperature and Thermal Energy

3 3 Ways to Transfer Thermal Energy Energy transfers from one object to another This transfer of energy as heat (thermal energy) as particles collide or objects collide is called conduction. Kinetic energy is transferred when these faster-moving atoms collide with slower- moving particles. Transferring Thermal Energy Conduction

3 3 Convection Convection is the transfer of thermal energy in a fluid by the movement of fluid from place to place. Transfer of energy by the movement of fluids with different temperatures. Transferring Thermal Energy A fluid expands as its temperature increases. The density of the fluid therefore decreases.

3 3 Convection Current Flow of a fluid due to heating and cooling Warm fluids rise because they expand and become less dense (lighter), then cool. Transferring Thermal Energy The warm water transfers thermal energy to the cooler water around it.

3 3 Convection Transferring Thermal Energy As the warm fluids cool, they contract and get heavier (denser) and sink. As fluids sink they are warmed up again by the heat source. The rising and sinking water forms a convection current.

3 3 Radiation Radiation is the transfer of energy by electromagnetic waves. Transferring Thermal Energy Radiation can pass through solids, liquids, and gases, but the transfer of energy by radiation is most important in gases. Examples: light, ultraviolet light, infrared light, sunlight, microwaves, x-rays Does not involve the movement of matter.

3 3 Radiation Transferring Thermal Energy When radiation strikes a material, some energy is absorbed, some is reflected, and some may be transmitted through the material.

3 3 Transferring Thermal Energy Conductors and Insulators 1.Conductor – material through which energy transfers easily - Examples – metals (energy transfers between particles easily)  solids (not all solids) tend to be better conductors  gases tend to be poor conductors

Conductors and Insulators 2.Insulator – material that poorly transfers energy - Examples – wood, plastic, rubberized materials, air, water