# Understanding Heat Transfer Conduction Convection and Radiation Heat

• Slides: 40

Understanding Heat Transfer, Conduction, Convection and Radiation

Heat Transfer Heat always moves from a warmer place to a cooler place. n Hot objects in a cooler room will cool to room temperature. n Cold objects in a warmer room will heat up to room temperature. n

Question If a cup of coffee and a red popsickle were left on the table in this room what would happen to them? Why? n The cup of coffee will cool until it reaches room temperature. The popsickle will melt and then the liquid will warm to room temperature. n

Heat Transfer Methods n Heat transfers in three ways: n Conduction n Convection n Radiation

Conduction When you heat a metal strip at one end, the heat travels to the other end. As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on, the vibrations are passed along the metal and so is the heat. We call this? Conduction

Why does metal feel colder than wood, if they are both at the same temperature? Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

Water movement Cools at the surface Cooler water sinks Convection current Hot water rises

Why is it windy at the seaside?

Cold air sinks Where is the freezer compartment put in a fridge? It is put at the top, because cool air sinks, so it cools the food on the way down. Freezer compartment It is warmer at the bottom, so this warmer air rises and a convection current is set up.

The third method of heat transfer How does heat energy get from the Sun to the Earth? ? There are no particles between the Sun and the Earth so it CANNOT travel by conduction or by convection. RADIATION

Radiation travels in straight lines True/False Radiation can travel through a vacuum True/False Radiation requires particles to travel True/False Radiation travels at the speed of light True/False

Emission experiment Four containers were filled with warm water. Which container would have the warmest water after ten minutes? Dull metal Shiny black Dull black shiny metal container would be the warmest after ten The _____ radiation back minutes because its shiny surface reflects heat _______ dull black container into the container so less is lost. The ____ emitting heat would be the coolest because it is the best at _______ radiation.

Absorption experiment Four containers were placed equidistant from a heater. Which container would have the warmest water after ten minutes? Dull metal Shiny black Dull black dull black container would be the warmest after ten The _____ radiation the best. minutes because its surface absorbs heat _______ shiny metal container would be the coolest because it is The _____ the poorest at _____ absorbing heat radiation.

Convection questions Why does hot air rise and cold air sink? Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air. Why are boilers placed beneath hot water tanks in people’s homes? Hot water rises. So when the boiler heats the water, and the hot water rises, the water tank is filled with hot water.

Radiation questions Why are houses painted white in hot countries? White reflects heat radiation and keeps the house cooler. Why are shiny foil blankets wrapped around marathon runners at the end of a race? The shiny metal reflects the heat radiation from the runner back in, this stops the runner getting cold.

1. Which of the following is not a method of heat transfer? A. Radiation B. Insulation C. Conduction D. Convection

2. In which of the following are the particles closest together? A. Solid B. Liquid C. Gas D. Fluid

3. How does heat energy reach the Earth from the Sun? A. Radiation B. Conduction C. Convection D. Insulation

4. Which is the best surface for reflecting heat radiation? A. Shiny white B. Dull white C. Shiny black D. Dull black

5. Which is the best surface for absorbing heat radiation? A. Shiny white B. Dull white C. Shiny black D. Dull black

Earth’s Atmosphere Why is it so important to life on earth?

Earth’s atmosphere is made up of 5 different layers…

Did you know that The Science Monkey’s Took Evan? Say it with me… n n n The Science Monkey’s Took Evan

I know you are thinking…what is he talking about? ? ? n n n The Science Monkey’s Took Evan MEANS…. n n n Troposphere Stratosphere Mesosphere Thermosphere Exosphere THE FIVE LAYERS OF THE EARTH’S ATMOSPHERE FROM THE EARTH OUT!

Why is the atmosphere divided into 5 different layers? n Any guesses? n n n The atmosphere is divided into five different layers because the atmosphere is not uniform, its properties change with altitude. Two properties change with altitude, the AIR PRESSURE and the AIR TEMPERATURE Lets look at each layer individually.

The first layer of the atmosphere is the… TROPOSPHERE n n n The troposphere is the layer of the atmosphere nearest to earth. The troposphere goes from 0 km to 16 km. All weather happens in the troposphere. More than half the air in the total atmosphere is in this layer. The temperature drops as the altitude increases. Harmful ozone is found here…IT CREATES SMOG!

What is OZONE? n A gaseous layer in the upper atmosphere that protects the earth from harmful ultraviolet radiation. At lower levels, ozone becomes a major pollutant. What is SMOG? n Pollution formed by the interaction of pollutants and sunlight (photochemical smog), usually restricting visibility, and occasionally hazardous to health.

n n n The second layer of the atmosphere is the… The stratosphere goes from STRATOSPHERE 16 km to 50 km. The temperature goes up with altitude. Most jets fly in this layer. The protective ozone is at the top of the atmosphere (It protects us from the ultraviolet radiation of the sun. ) Rivers of air, called Jet Streams, can be found at the base of this layer.

The third layer of the atmosphere is the… MESOSPHERE n n n The Mesosphere goes from 50 km to 90 km. In the mesosphere, the temperature drops with altitude. The mesosphere is the coldest layer of the atmosphere. Meteors burn up in this layer. Radio waves are reflected back to earth in the mesosphere.

The fourth layer of the atmosphere is the… THERMOSPHERE n n n The thermosphere goes from 90 km to 300 km. In thermosphere the temperature goes up with altitude. The thermosphere is the hottest layer of the atmosphere. Curtains of light called auroras occur in this layer. The Ionosphere is found in thermosphere. This is the component of thermosphere that makes the auroras.

The last layer of the atmosphere is the… EXOSPHERE n n n The exosphere is the outermost layer of the atmosphere. The temperature in the exosphere goes up with altitude. Satellites orbit earth in the exosphere.

It is important to understand the different characteristics of the earth’s atmosphere. As you go through the following slides, challenge your partner to see who can name the correct layer in which each characteristic can be found. GOOD LUCK!

EXOSPHERE

MESOSPHERE

THERMOSPHERE

TROPOSPHERE

STRATOSPHERE

THERMOSPHERE OR THE IONOSPHERE

MESOSPHERE

Now that you are all experts on the atmosphere…continue with your study of meteorology!