Heat

Unit A : Chapter 1 : Section 1

Temperature Depends on Kinetic Energy Kinetic Energy is the energy of motion The faster the particles of matter move, the more kinetic energy they have

What is Temperature? Measuring Temperature Temperature is a measure of the Average Kinetic Energy of a substance This means: When you measure temperature, you are measuring the average motion of the atoms

What is the difference between temperature and heat? Temperature is a measure of the average kinetic energy of atoms. Thermometersare used to measure temperature In other words: the faster the atoms move = the higher the temperature, & the slower the atoms move = the lower the temperature. Less Heat More Heat

What happens when you use a thermometer to measure temperature? What is Temperature? What Do You Think? What happens when you use a thermometer to measure temperature?

What is Temperature? Temperature is expressed by one of 3 scales:

Which is warmer, the tile or the rug on a bathroom floor? What is Heat? What Do You Think? Which is warmer, the tile or the rug on a bathroom floor?

What is Heat? Heat- A Transfer of Energy Heat depends on how fast particles are moving AND how many particles there are.

Unit A : Chapter 1 : Section 1 What is heat? This means- the more particles that make up an object, the more heat energy it has… Unit A : Chapter 1 : Section 1

Unit A : Chapter 1 : Section 1

Unit A : Chapter 1 : Section 1 Same amount of liquid. Which one has greater available thermal energy? How do you know? Unit A : Chapter 1 : Section 1

Which is warmer, the tile or the rug on a bathroom floor? What is Heat? What Do You Think? Which is warmer, the tile or the rug on a bathroom floor?

Hot objects contain more thermal energy than cold objects. Another word for heat is THERMAL ENERGY. Hot objects contain more thermal energy than cold objects.

Unit A : Chapter 1 : Section 1 Heat Transfer Heat is the transfer of energy between objects or particles that are at different temperatures Unit A : Chapter 1 : Section 1

What is Heat? Heat- A Transfer of Energy Energy moves from the warmer object to the cooler object until both are the same temperature. This is known as Thermal Equilibrium

Unit A : Chapter 1 : Section 1 Thermal Equilibrium Unit A : Chapter 1 : Section 1

No energy transfer occurs THERMAL EQUILIBRIUM No energy transfer occurs

The point at which two objects reach the same temperature. THERMAL EQUILIBRIUM The point at which two objects reach the same temperature. -Whenever they reach the same temperature, then no more energy transfer is taking place.

No energy transfer occurs THERMAL EQUILIBRIUM No energy transfer occurs

Unit A : Chapter 1 : Section 1

What is Heat? Reaching Thermal Equilibrium

What is Temperature? Thermal Expansion- As temperature rises, volume (size) increases

What is Temperature? Thermal Expansion The asphalt in the road expands when heated and contracts when cooled This results in cracks and potholes due to Thermal Expansion

THERMAL EXPANSION The spreading of particles (atoms) and increased volume (size) when an object is heated is known as THERMAL EXPANSION

THERMAL EXPANSION. If energy is added to atoms, they move faster. The faster they move, the further apart they move. This spreading out of atoms happens in solids, liquids and gases. Thermal expansion is why running a tight jar lid under warm water loosens the lid. *pg 154

What is Temperature? Thermal Expansion When the metal rails in this picture heated up, they increased in length and volume Thermal Expansion caused the rails to buckle and bend

Unit A : Chapter 1 : Section 1 Density & Heat Density=the amount of matter in a given space/volume. Can we change the density of an object? Unit A : Chapter 1 : Section 1

Unit A : Chapter 1 : Section 1 Density & Heat When does an object’s density change? -When heat is added or removed. Think about thermal expansion & what happens to the molecules/atoms when heated/cooled… Unit A : Chapter 1 : Section 1

Unit A : Chapter 1 : Section 1 Density & Heat When object is HEATED- molecules spread out- object LESS DENSE When object is COOLED- molecules come together- object MORE DENSE Unit A : Chapter 1 : Section 1

Why does this happen? Hot air balloon rises Basketball or bike tire goes flat in winter Atmosphere changes as you climb a mountain Perfume can be smelled all over the room

Why are some objects less dense than other objects? As the molecules of a substance spread apart, the density of the substance is lowered. What causes molecules to spread? Adding energy so the movement of the molecules increases.

What is Heat? Energy is Transferred by 3 Methods:

What is Heat? Conduction is the transfer of thermal energy through direct contact Hold a metal wire in a flame and energy travels from atom to atom until it burns your hand

CONDUCTION Transfer of heat from one substance to another by direct contact. Happens within and between objects that touch each other Examples: Sauce pan on a stove top, metal spoon in a bowl of soup, ice melting in a warm hand, hot shower, walking on hot coals

Objects that heat up easily are called CONDUCTORS. Metals are the best conductors Metal objects feel cold because they conduct heat AWAY from your hand Objects that DO NOT heat up easily are called INSULATORS. Things like glass,wood, plastic and rubber are good insulators

Which parts of the pan are conductors and which are insulators?

Which is warmer, the tile or the rug on a bathroom floor? What is Heat? What Do You Think? Which is warmer, the tile or the rug on a bathroom floor?

What is Heat? Convection Convection is the transfer of thermal energy by the movement of a liquid or a gas Convection is seen as hot material rises and cool material sinks

CONVECTION Transfer of heat in liquids and gases ONLY Heat moves up and down in a circular motion called a CONVECTION CURRENT Heated liquids and gases are less dense & rise carrying heat with them Examples: hang gliders, soaring birds, home furnace heating & circulating air

Convection currents cause the Earth’s tectonic plates to move about.

What is Heat? Radiation Radiation is the transfer of energy through matter or space through light energy, such as visible light and infrared waves Radiation is the only type of energy transfer where the objects don’t have to touch

RADIATION transfer of heat through empty space in form of infrared radiation waves (what we think of as heat waves) Examples: blacktop heats up on a sunny day, hot sand on a beach, electric heaters.

Explain how each of these uses radiant heat.

Unit A : Chapter 1 : Section 1 Web Sites to Visit: Harcourt Science: States of Matter BBC: Science BrainPop: States of Matter Unit A : Chapter 1 : Section 1