Thermal Energy Chapter 9

Welcome Back Activity  Take out a blank piece of notebook paper  You may share one with your partner and just have half a sheet  DO NOT WRITE YOUR NAME ON THE PAPER  Write down the best thing you did over winter break, KEEP IT APPROPRIATE  Do not share your answer with anyone  Take out a blank piece of notebook paper  You may share one with your partner and just have half a sheet  DO NOT WRITE YOUR NAME ON THE PAPER  Write down the best thing you did over winter break, KEEP IT APPROPRIATE  Do not share your answer with anyone

Mid-Year Evaluation  What three things helped you learned best in this class last semester?  What three things do you think Ms. Nelson can get rid of because they did not help you learn the material?  What three things helped you learned best in this class last semester?  What three things do you think Ms. Nelson can get rid of because they did not help you learn the material?

Textbook Questions  On the back of your graphic organizer answer questions 1-5 from page 259 in your textbook

Temperature & Thermal Energy Chapter 9, Section 1

Kinetic Theory of Matter o Kinetic theory: matter is composed of particles that are always in random motion o These particles have kinetic energy (KE) because they are in motion o When the particles collide, they can transfer kinetic energy (KE) from one particle to another o Kinetic theory: matter is composed of particles that are always in random motion o These particles have kinetic energy (KE) because they are in motion o When the particles collide, they can transfer kinetic energy (KE) from one particle to another

Temperature o Temperature: a measure of the average kinetic energy of its particles o As the speed of particles increases, the temperature of the substance increases o The SI unit for temperature is the Kelvin (K) o Temperature: a measure of the average kinetic energy of its particles o As the speed of particles increases, the temperature of the substance increases o The SI unit for temperature is the Kelvin (K)

Temperature Conversions

Practice: 1.What is the temperature in Kelvin of a solution that measures 78˚C? 2.What is -42˚F in degrees Celsius? 3.What is the temperature of 22˚C in degrees Fahrenheit? 1.What is the temperature in Kelvin of a solution that measures 78˚C? 2.What is -42˚F in degrees Celsius? 3.What is the temperature of 22˚C in degrees Fahrenheit?

Thermal Energy o Particles that make up matter are in constant motion o They thus have kinetic energy (KE) o Particles also exert attractive electric forces on each other o They thus have potential energy (PE) that increases the further apart they get o Thermal energy: the sum of kinetic and potential energies of all particles in an object o Particles that make up matter are in constant motion o They thus have kinetic energy (KE) o Particles also exert attractive electric forces on each other o They thus have potential energy (PE) that increases the further apart they get o Thermal energy: the sum of kinetic and potential energies of all particles in an object

Heat o Heat: thermal energy that flows from something at a higher temperature to something at a lower temperature o Thermal energy always flows from a warmer to a cooler material o Specific heat: the amount of thermal energy needed to raise the temperature of 1 kg of some material by 1˚C o Units = J/ (kg˚C) o Heat: thermal energy that flows from something at a higher temperature to something at a lower temperature o Thermal energy always flows from a warmer to a cooler material o Specific heat: the amount of thermal energy needed to raise the temperature of 1 kg of some material by 1˚C o Units = J/ (kg˚C)

Changes in Thermal Energy

Practice! 1.The air in a living room has a mass of 72 kg and a specific heat of 1,010 J/(kg˚C). What is the change in thermal energy of the air when it warms from 20˚C to 25˚C?

Measuring Specific Heat  Calorimeters are used to measure specific heat  A heated sample transfers thermal energy to a known mass of water  The energy absorbed by the water can be calculated by measuring the water’s temperature change  The thermal energy released by the sample is equal to the thermal energy absorbed by the water  Calorimeters are used to measure specific heat  A heated sample transfers thermal energy to a known mass of water  The energy absorbed by the water can be calculated by measuring the water’s temperature change  The thermal energy released by the sample is equal to the thermal energy absorbed by the water

Specific Heat Demo

Specific Heat  Using what we know about specific heat, make a hypothesis about what substance will heat up the fastest when the same amount of heat is applied to each substance.

States of Matter Chapter 9, Section 2

Four States of Matter o Solids  o Particles are packed closely together o Particles vibrate in place o Definite volume o Definite shape o Liquids  o Attractive forces between particles are weaker than in solids o Particles slide past each other o Definite volume o Indefinite shape (takes shape of container) o Solids  o Particles are packed closely together o Particles vibrate in place o Definite volume o Definite shape o Liquids  o Attractive forces between particles are weaker than in solids o Particles slide past each other o Definite volume o Indefinite shape (takes shape of container)

Four States of Matter o Gases  o Attractive forces between particles are weak (they don’t cling together) o Particles spread further apart until evenly distributed (diffusion) o Indefinite volume o Indefinite shape o Plasma  o Most common state of matter in the universe o Consists of positively and negatively charged particles o Indefinite volume o Indefinite shape o Ex: stars, lightning, neon, fluorescent tubes, auroras o Gases  o Attractive forces between particles are weak (they don’t cling together) o Particles spread further apart until evenly distributed (diffusion) o Indefinite volume o Indefinite shape o Plasma  o Most common state of matter in the universe o Consists of positively and negatively charged particles o Indefinite volume o Indefinite shape o Ex: stars, lightning, neon, fluorescent tubes, auroras

Changing States o Melting  o As temperature increases, particles move faster, causing attractive forces to weaken and slip out of their ordered arrangement o The temperature at which a solid melts is the melting point o Heat of fusion: the amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point o Melting  o As temperature increases, particles move faster, causing attractive forces to weaken and slip out of their ordered arrangement o The temperature at which a solid melts is the melting point o Heat of fusion: the amount of energy required to change 1 kg of a substance from a solid to a liquid at its melting point

Changing States o Freezing  o The heat of fusion is also the energy released when a liquid freezes, or changes to a solid o If you lower the liquid’s temperature, you decrease the average kinetic energy of the particles and they move slower o The attractive forces will become strong enough to hold them in place in an orderly structure o Freezing  o The heat of fusion is also the energy released when a liquid freezes, or changes to a solid o If you lower the liquid’s temperature, you decrease the average kinetic energy of the particles and they move slower o The attractive forces will become strong enough to hold them in place in an orderly structure

Changing States o Vaporization  o As temperature increases, liquid particles move faster and become spread apart o The forces between particles weaken and they no longer cling together o The liquid forms a gas o Vaporization that occurs at the surface of a liquid = evaporation o Particles in the gas state have a higher energy o Vaporization  o As temperature increases, liquid particles move faster and become spread apart o The forces between particles weaken and they no longer cling together o The liquid forms a gas o Vaporization that occurs at the surface of a liquid = evaporation o Particles in the gas state have a higher energy

Changing States o Boiling  o Occurs throughout a liquid o Occurs only at a specific temperature depending on the pressure on the surface of the liquid o The boiling point is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface o Heat of vaporization: amount of energy required for 1 kg of the liquid at its boiling point to become a gas o Boiling  o Occurs throughout a liquid o Occurs only at a specific temperature depending on the pressure on the surface of the liquid o The boiling point is the temperature at which the pressure of the vapor in the liquid is equal to the external pressure acting on its surface o Heat of vaporization: amount of energy required for 1 kg of the liquid at its boiling point to become a gas

Changing States o Condensation  o The heat of vaporization is also the amount of energy released during condensation o Occurs when a gas changes into a liquid o The average kinetic energy of the water particles is decreased, and the water vapor changes to a liquid o Ex: dew, sides of glass of iced drink on hot day o Condensation  o The heat of vaporization is also the amount of energy released during condensation o Occurs when a gas changes into a liquid o The average kinetic energy of the water particles is decreased, and the water vapor changes to a liquid o Ex: dew, sides of glass of iced drink on hot day

Heating Curve o A heating curve shows the temperature change of water as thermal energy is added

Thermal Expansion o According to kinetic theory, particles in an object are in constant motion o The speed of particles increases as the temperature of the object increases o As particles move faster, the attractive forces between them weakens, and the distance between the particles increases o This results in an expansion of the object (object’s size increases) o When the object cools, the opposite happens o According to kinetic theory, particles in an object are in constant motion o The speed of particles increases as the temperature of the object increases o As particles move faster, the attractive forces between them weakens, and the distance between the particles increases o This results in an expansion of the object (object’s size increases) o When the object cools, the opposite happens

Thermal Expansion

Transferring Thermal Energy Chapter 9, Section 3

Conduction o Conduction: the transfer of thermal energy between colliding particles o Kinetic energy is transferred when fast- moving atoms collide with slower- moving particles o The rate at which thermal energy is transferred depends on the material o The conduction in solids and liquids is faster than in gases o Conduction: the transfer of thermal energy between colliding particles o Kinetic energy is transferred when fast- moving atoms collide with slower- moving particles o The rate at which thermal energy is transferred depends on the material o The conduction in solids and liquids is faster than in gases

Convection o Convection: the transfer of thermal energy in a fluid by the movement of fluid from place to place o As the particles increase in energy, they travel faster, and the fluid expands and the density of the fluid decreases o Convection: the transfer of thermal energy in a fluid by the movement of fluid from place to place o As the particles increase in energy, they travel faster, and the fluid expands and the density of the fluid decreases

Convection o The differences between warmer and cooler fluids can cause convection currents to occur o The rising and sinking of various densities causes a convection current o Ex: Temperature differences in geographical regions cause convection currents that transfer thermal energy to cooler regions o The differences between warmer and cooler fluids can cause convection currents to occur o The rising and sinking of various densities causes a convection current o Ex: Temperature differences in geographical regions cause convection currents that transfer thermal energy to cooler regions

Radiation o Radiation: the transfer of energy by electromagnetic waves o These waves do not require a medium (i.e. they travel through space where no matter is present) o Radiation can pass through solids, liquids, and gases o Radiation: the transfer of energy by electromagnetic waves o These waves do not require a medium (i.e. they travel through space where no matter is present) o Radiation can pass through solids, liquids, and gases

Radiation o When radiation strikes a material, some energy is absorbed, some is reflected, and some is transmitted through the material o Light-colored materials reflect more radiant energy o Dark-colored materials absorb more radiant energy o When a material absorbs radiant energy, its thermal energy increases o When radiation strikes a material, some energy is absorbed, some is reflected, and some is transmitted through the material o Light-colored materials reflect more radiant energy o Dark-colored materials absorb more radiant energy o When a material absorbs radiant energy, its thermal energy increases

Heat Transfer

Thermal Insulators o Thermal insulator: a material in which thermal energy moves slowly o Ex: wood, some plastics, fiberglass, air o Materials that are good conductors of thermal energy are poor thermal insulators o Thermal insulator: a material in which thermal energy moves slowly o Ex: wood, some plastics, fiberglass, air o Materials that are good conductors of thermal energy are poor thermal insulators

Thermal Insulators o Materials that contain pockets of trapped air are good insulators because the air pockets are poor conductors of thermal energy so they trap thermal energy inside o Ex: Winter jackets o Materials that contain pockets of trapped air are good insulators because the air pockets are poor conductors of thermal energy so they trap thermal energy inside o Ex: Winter jackets