Thermal Energy Internal energy: energy of the moving particles that compose matter

Starter Questions 1. 2.How does a thermometer work 3.Fold a piece of notebook paper to form three columns-cond, conv and radi 4. solve problems on pg If you touch two different objects having the same temperature, how could one object feel colder than the other?

Starter 3 Thermal Energy Transfer Read Ch Fold a piece of notebook paper to form three columns –Head each column with one of the three ways that thermal energy can be transferred –Define each –List three main points from the reading for each thermal energy transfer process On the back of the paper, prepare an example illustrating how each transfers heat

Key Terms and Ideas Thermal Energy Kinetic Theory Heat Thermal Equilibrium and heat transfer Kinetic Theory as it relates to expansion and contraction Hot vs. cold

Physics and Particles Particle is a general term used to describe molecules, atoms and sub-atomic particles

The higher the temperature of a substance, the faster the motion of its molecules. This is also referred to as the Kinetic Theory— a)all matter is made of atoms and molecules that are moving. b)The higher the temperature, the faster the particles move. c)Given the same temperature, heavier particles move slower than lighter particles Temperature

Increasing Avg. KE Increasing Temp. solid liquid gas Particle speed is increasing Matter is changing state melting evaporation condensation freezing

solid liquid gas Particle speed is Matter is changing state

Temperature and Kinetic Energy Temperature is related to the average kinetic energy of the atoms and molecules in a substance. The faster the molecules move, the ______________ the temperature and the _____________ the average kinetic energy and the __________ the particle speed Temperature greater

1.Heat is the quantity of thermal energy transferred 2.Heat always flows from a substance with a higher temperature to a substance with a lower temperature. 3.Heat flows only when there is a difference in temperature. 4.Heat units are calories or joules Heat

Just as water will not flow uphill by itself, regardless of the relative amounts of water in the reservoirs, heat will not flow from a cooler substance into a hotter substance by itself Heat hotter colder Entropy! Flow from higher to lower energy state.

What causes heat to flow? 21.2 Heat A difference in temperature between objects in thermal contact.

When a substance takes in or gives off heat, its internal energy changes Internal Energy

Heat flows between two objects of different temperature until they have the same temperature. The loss of thermal energy from the warmer object equals the gain of thermal energy for the cooler object 21.3 Thermal Equilibrium What happens when a warmer substance comes in contact with a cooler substance?

Most forms of matter—solids, liquids, and gases— expand when they are heated and contract when they are cooled Thermal Expansion

When the temperature of a substance is increased, its molecules jiggle faster and normally tend to move farther apart. This results in an expansion of the substance. Gases generally expand or contract much more than liquids. Liquids generally expand or contract more than solids Thermal Expansion

Starter Question #2 How does a thermometer work? The kinetic theory be used to explain expansion and contraction of materials when the temperature of the material changes. As the temperature rises, heat is transferred from the surroundings to the liquid inside the thermometer and the molecules that compose the liquid vibrate faster. This causes the liquid to expand and rise. As the temperature falls, heat is transferred away from the liquid inside to the surroundings and the molecules that compose this liquid slow down. This causes the liquid to contract.

The liquid in the thermometer stops rising or falling when thermal equilibrium is reached (no more heat flow!) Air temperature = Liquid temperature

Do copper, clay and water have the same chemical composition? No. Copper is composed of Cu atoms and water is composed of H 2 O molecules. Clay is a complex silicate. The difference in chemical composition influences how copper, clay and water respond when heat is transferred Specific Heat Capacity The specific heat capacity of a substance is the quantity of heat required to raise 1 g of a substance by 1 degree Celsius.

The amount of heat required to raise the temperature of 1 kg of a substance by 1 degree C (or 1 K). Q = c m Δ T 21.6 Specific Heat Capacity

A substance with a high specific heat capacity can absorb a large quantity of heat before it will raise in temperature (water has a high specific heat). A substance with a low specific heat requires relatively little heat to raise its temperature (copper has a low specific heat) Specific Heat Capacity

highest lowest

think! Which has a higher specific heat capacity—water or sand? Explain Specific Heat Capacity

think! Which has a higher specific heat capacity—water or sand? Explain. Answer: Water has a greater heat capacity than sand. Water is much slower to warm in the hot sun and slower to cool at night. Sand’s low heat capacity, shown by how quickly it warms in the morning and how quickly it cools at night, affects local climates Specific Heat Capacity Good conductors have a low specific heat capacity!

A gram of water requires 1 calorie of energy to raise the temperature 1°C. It takes only about one eighth as much energy to raise the temperature of a gram of iron by the same amount Specific Heat Capacity The capacity of a substance to store heat depends on its chemical composition.

21.6 Specific Heat Capacity

6. What is the difference between a substance with a high specific heat and a low specific heat capacity?

Substances with a low specific heat (e.g., metals) need very little heat to raise temperature –Good conductors, not good absorbers, do not hold onto heat well Substances with a high specific heat need a large quantity of heat to raise temperature. –Poor conductors, good absorbers, store and hold onto heat well

7.How does the specific heat of water help to moderate climate?

Friday 1.Heat Flow Examples—Home Heating and Cooling a)Summer time flow b)Winter time flow 2.Water and Specific Heat a)Sea Breezes b)Moderating effect of water (Edmonton vs. Cork) 3.Reason for the seasons a)Tilt of Earth’s Rotational Axis (23.5 o ) b)Insolation Angle (same radiation, different area) c)Absorption vs. Reflection

Winter Vs. Summer Heat Flow In winter -Heat loss from inside (warmer) to outside (colder) -Heating system must operate to transfer thermal energy from fuel to fluid to room to keep house warm In summer -Heat gain from outside (warmer) to inside (cooler) - Cooling system must operate to transfer incoming heat entering the house back to the outside

Why do we need heating systems? What do the green arrows represent? How does this heat flow affect the temperature of the air inside the home? Where does the energy come from that increases the temperature of the air inside the home?

Explain why the heat flow for a home is different in the winter vs. the summer.

Convection currents are produced by uneven heating. a.During the day, the land is warmer than the air, and a sea breeze results Convection

Convection currents are produced by uneven heating. a.During the day, the land is warmer than the air, and a sea breeze results. b.At night, the land is cooler than the water, so the air flows in the other direction Convection

Generation of Sea Breezes Day Land low specific heat heat and cools rapidly less resistant to temperature change Sea high specific heat heats and cools slowly more resistant to temperature change Sea breeze Air above the land heats more rapidly and rises Air above the sea remains cooler and moves on land to replace the land air that rose Convection

Generation of Sea Breezes Night Air above the water is warmer than the air above the land and rises Air above the ground is cooler than the air above the water and moves over the sea to replace the sea air that rose Land low specific heat heat and cools rapidly less resistant to temperature change Sea high specific heat heats and cools slowly more resistant to temperature change Land Breeze

Generation of Sea Breezes

The property of water to resist changes in temperature improves the climate in many places The High Specific Heat Capacity of Water

Water has a high specific heat and is transparent, so it takes more energy to heat up than land does The High Specific Heat Capacity of Water

Moderating Effect of Water During the summer, surrounding air is cooled by the water and keeps the coast cooler than the intercontinental locations. During the winter, the surrounding air is warmed by the water and keeps the coast warmer than the intercontinental locations.

Water’s capacity to store heat affects the global climate. Water stores and hold heat well because of its high specific heat The High Specific Heat Capacity of Water Gulf Stream brings warm water northeast from the Caribbean.

The Gulf Stream (warm water from equator) meets The Labrador Current (cold water from polar region) Gulf Stream Labrador Current Thermal Front

Climate of Europe Look at a world globe and notice the high latitude of Europe. Both Europe and Canada get about the same amount of the sun’s energy per square kilometer The High Specific Heat Capacity of Water

Cork Edmonton Same insolation angle, different climate due to proximity to water and the warming effect from the Gulf Stream Continental Climate Marine Climate

The Gulf Stream brings warm winters to Ireland and the prevailing winds off the Atlantic carry with them rain. It means grass can grow almost all year round — creating the lush sweeping pastures of the Emerald Isle. Today they make up 93 percent of all farmland. No other country in Europe has quite as much grass as Ireland.

Climate of America On the west coast, air moves from the Pacific Ocean to the land. In winter, the water warms the air that moves over it and warms the western coastal regions of North America. In summer, the water cools the air and the western coastal regions are cooled The High Specific Heat Capacity of Water The central interior of a large continent usually experiences extremes of temperature. Land, with a lower specific heat capacity, gets hot in summer but cools rapidly in winter.

Heat can be transferred by conduction, by convection, and by radiation.

In conduction, collisions between particles transfer thermal energy, without any overall transfer of matter Conduction

Heat from the flame causes atoms and free electrons in the end of the metal to move faster and jostle against others. The energy of vibrating atoms increases along the length of the rod Conduction

In convection, heat is transferred by movement of the hotter substance from one place to another Convection

Convection occurs in all fluids. a.Convection currents transfer heat in air Convection Hot, less dense fluid rises in the presence of cooler, more dense fluid.

Convection occurs in all fluids. a.Convection currents transfer heat in air. b.Convection currents transfer heat in liquid Convection When fluid particles at the bottom of the pan begin to vibrate faster, they expand and decrease in density, making the hotter fluid more buoyant.

In radiation, heat is transmitted in the form of radiant energy, or electromagnetic waves Radiation

Heat Transfer 1 Which heat transfer occurs from particle to particle during direct contact of substances? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 1 Which heat transfer occurs from particle to particle during direct contact of substances? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 2 Which heat transfer can occur through a vacuum or through matter? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 2 Which heat transfer can occur through a vacuum or through matter? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 3 Which heat transfer is based on density differences in a substance and gravity? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 3 Which heat transfer is based on density differences in a substance and gravity? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 4 Which heat transfer occurs through the movement of the heated substance? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 4 Which heat transfer occurs through the movement of the heated substance? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 5 Which heat transfer is characterized by transmission by electromagnetic waves? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 5 Which heat transfer is characterized by transmission by electromagnetic waves? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 6 Which heat transfer processes can only occur through matter? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Heat Transfer 6 Which heat transfer processes can only occur through matter? a)Conduction b)Convection c)Radiation d)Conduction and Convection e)Conduction, convection and radiation

Most of the heat from a fireplace goes up the chimney by convection. The heat that warms us comes to us by radiation Radiation

Radiation is caused by moving electrons or charged particles in matter. The faster the particles move, the higher the frequency of the electromagnetic radiation.

a.Radio waves send signals through the air Radiation

a.Radio waves send signals through the air. b.You feel infrared waves as heat Radiation

a.Radio waves send signals through the air. b.You feel infrared waves as heat. c.A visible form of radiant energy is light waves Radiation

11. What happens to the frequency of radiant energy as the temperature of the substance increases or decreases?

The frequency of radiant energy increases as the temperature of the substance increases.