Temperature and Thermal Energy 1 Temperature and energy

Temperature and Thermal Energy 1 Temperature and energy Glencoe: Chapter 9 – Section 1: pages 254 -259

Temperature and Thermal Energy 1 Kinetic Theory of Matter • 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.

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

Temperature and Thermal Energy 1 • Here is a picture showing the three temperature scales side by side

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

Temperature and Thermal Energy 1 Temperature 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 rise up the tube

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

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

Temperature and Thermal Energy 1 Temperature 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

Temperature and Thermal Energy 1 Temperature • 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

Temperature and Thermal Energy 1 Thermal Energy • The sum of the kinetic and potential energies of all the particles in an object is 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.

Temperature and Thermal Energy 1 Heat • 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**

Transferring Thermal Energy 3 Ways to Transfer Thermal Energy Conduction • 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 slowermoving particles.

Transferring Thermal Energy 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. • A fluid expands as its temperature increases. • The density of the fluid therefore decreases.

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

Transferring Thermal Energy 3 Convection • 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.

Transferring Thermal Energy 3 Radiation • Radiation is the transfer of energy by electromagnetic waves. • 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.

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

Transferring Thermal Energy 3 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