Presentation on theme: "HEAT. What do you think this photograph shows? ENERGY of HEAT It takes heat to shape glass or to make a cup of tea."— Presentation transcript:
What do you think this photograph shows?
ENERGY of HEAT It takes heat to shape glass or to make a cup of tea.
Temperature measures how hot or cold something is. Energy moves between objects that have different temperatures. HEAT is energy that moves between objects of different temperatures. The difference in temperatures makes the energy move back and forth.
Temperature is measured in different scales. The two scales on this thermometer are CELSIUS and FAHRENHEIT.
Clothing traps heat near our body. Water coming from a shower head is hotter than the air around it. Ice cubes melt as heat transfers to them from the warm air. Heat moves from the burner to the pan, to the water, and then to vapor, to the air.
This is dry ice – frozen carbon dioxide. It is about -80 degrees Celsius / -112 degrees Fahrenheit
HEAT on the MOVE Heat moves from your hand to the snow and the snow melts. Your hand feels cold.
Heat is CONDUCTED from the soup to the spoon. Soon the spoon feels hot.
CONDUCTION Conduction is the transfer or movement of heat between two objects that are touching. Conduction can also occur within an object. Heat moves from inside your body to warm your skin. Your feet and hands stay warm because heat is moving all around your body.
CONVECTION Convection is the transfer of heat within a liquid or a gas. Particles in liquids and gases move more easily because they are farther apart. The particles take heat with them. Heat from a campfire warms the air around it by convection.
Hot air rises above the cooler air in the balloon. Thats what keeps a hot-air balloon in flight.
Heat is conducted from the burner to the pot and then to the water. Heated water travels up, warming the cool water above. Cooler water sinks to the bottom, where it gets heated. The cycle repeats – this is called CONVECTION CURRENT.
FEELING RADIANT Heat moves by conduction between solids that are touching. Heat moves by convection through gases and liquids.
Heat can also move as RADIATION. Radiation is the transfer of heat without matter to carry it. Heat leaves one object and goes instantly to another. Standing near a campfire you feel the warm air, you also feel the heat through radiation.
Heat from the sun radiates through space and through the atmosphere before it warms your face.
Heat radiating from this light keeps these chick eggs warm.
RADIATION is the transfer of heat without matter to carry it. Heat leaves one object and is transferred on to the other. Radiation is the most important way heat can move.
Life on Earth needs heat from the sun. But space is a vacuum. How does heat travel through the emptiness of space? by RADIATION!
Heat moves through some materials very easily. Heat from an oven moves easily into a pan. But heat from the pan did not pass through the oven mitt.
A material that allows heat to move through it easily is called a conductor. Many heat conductors also conduct electricity well.
Glass does not conduct heat well. If you pour boiling water into a metal bowl the outside of the bowl quickly gets hot. A glass bowl gets warm more slowly.
Boiling water in glass cup. Boiling water in metal pot.
Marble or stone does not conduct heat as well as metals do. But it can still conduct heat away from your body. Thats why marble feels cool when you touch it.
Metals are great heat conductors. Some metals conduct heat better than others do.
For the most part, solids are better conductors of heat than liquids or gases are. Thats because the particles that make up a solid are packed closely together. They vibrate, but they dont move apart very much. Heat can move quickly form one particle to another.
Look carefully at this experiment. What happened? Why?
Particles in the hot coffee have higher kinetic energy which transmits heat to the cup and ultimately to the air surrounding the cup.
But not all materials are conductors. Heat does not move easily through some materials. And it does not move at all through other materials. Materials that do not conduct heat well are called INSULATORS.
Oven mitts are insulators. They are made of materials that are poor conductors of heat. When you remove a pan of cookies from the oven, your hands dont get burned.
Gases can be good insulators. A thin layer of trapped air is an excellent insulator. In cold weather, layers of clothing trap your body heat near you. There is air between the layers of clothing. Along with the clothing, the air insulates your body.
Insulators can be used to slow down the movement of heat. Metal wires conduct electricity and heat. Most wires are covered in rubber to insulate them and keep people safe from the electricity and heat.
Hair is an Insulator Most furry animals stay warm in cold weather. Fur is made of thick hairs. Around each hair is air. The air and the fur act as insulators, keeping the animals warm.
How does a thermos work?
A thermos has a glass lining. This glass lining holds the cocoa or soup. Glass is not a good conductor of heat. Energy can even move in a vacuum. Using a reflective silver surface act like a mirror. It reflects some heat back. There is a vacuum between the inner and outer glass layers of the thermos bottle. The vacuum keeps conduction or convection from taking place. Using this system reduces conduction, convection, and radiation. The cocoa stays hot.
How can knowledge of insulation help us conserve energy?
When the weather is hot, you want to keep heat from coming into your home. When the weather is cold, you want to keep heat from leaving your home. It costs money to cool and heat a home. Heat leaving the home
There are different ways to slow the flow of heat into or out of a house. Some things need to be done while the house is being built. Others things can be done to an existing home. Insulating a home saves money. It also helps conserve energy.
The number 1 thing that can be done to conserve energy is insulation. Insulation is blown inside the walls of a house. Insulation keeps heat from traveling through to the attic. Insulation keeps heat from escaping through the walls.
The next thing that you can use to conserve energy is windows. New windows have two panes of glass to limit conduction. They also have a special coating that limits heat radiation.
Insulating pipes is another way to conserve energy. Hot pipes radiate heat from water into the air. Wrapping the pipes keeps the heat from escaping.
Soil is a great insulator. Basements are usually cool, even in the summer because soil covers the sides of basement walls.
REVIEW WORD BANK – WORDS MAY BE USED MORE THAN ONCE insulator conductor conduction convection radiation Heat moves easily through it: _______________________________ Heat does not move easily through it: ________________________ Solids often do this to heat: ________________________________ A thin layer of trapped air can do this to heat: _________________ Which forms of heat transfer do insulated bottles prevent: ______ ______________________________________________________ Wrapping hot water pipes prevent which form of heat transfer: ___ ______________________________________________________
REVIEW WORD BANK - CONDUCTION CONVECTION RADIATION Add hot water to bath ____________________________________ Space heater ____________________________________________ Iron-on decals ___________________________________________ Clothes dryer ____________________________________________ Sunlight through window _________________________________ Sandwich press __________________________________________