You walk into the bathroom in your bare feet. The temperature in there is 23 degrees Celsius. You step onto the tile floor and it feels very cold. Quickly, you step onto the throw rug in front of the sink, and the rug feels warmer. 1.Is the floor really colder than the rug? 2.Why do they seem to be at different temperatures when your bare feet touch them?
How is heat transferred through matter and space?
Ice-Cold Lemonade It was a hot summer day. Mattie poured herself a glass of lemonade. The lemonade was warm, so Mattie put some ice in the glass. After 10 minutes, Mattie noticed that the ice was melting and the lemonade was cold. She had 3 different ideas. Which idea do you think best explains why the lemonade got cold? A.The coldness from the ice moved into the lemonade. B.The heat from the lemonade moved into the ice. C.The coldness and the heat moved back and forth until the lemonade cooled off.
ANSWER B The heat from the lemonade moved into the ice. As the molecules in the warmer lemonade came in contact with the molecules in the cooler ice, heat energy flowed into the ice from the lemonade. This process cooled the lemonade and melted the ice.
High-Low Song High-Low, High-Low, That’s the way the heat will flow. (whistle) High-Low, High-Low, That’s the way the heat will flow.
All matter is made up of constantly moving particles. All moving things possess kinetic energy.
Temperature is a measure of the average kinetic energy of the particles in a sample of matter.
As the particles in a sample move faster and faster, the kinetic energy becomes greater and the temperature of the object rises.
Thermal energy is the total energy of the particles in a material. This total includes: 1.Kinetic energy – vibrations and movement within and between particles 2.Potential energy – forces that act within or between the particles (bonds)
Thermal energy depends on: 1.Mass – the greater the mass, the larger the number of moving particles 2.Temperature – the higher the temperature, the faster the particles are moving
Example – Temperature as a factor
Example –Mass as a factor
Heat is the thermal energy that flows from something with a higher temperature to something with a lower temperature. In most cases, heat flows from warmer to cooler materials.
Thermal energy travels as heat from a material of higher temperature to a material of lower temperature. Energy is transferred from your back to the stethoscope because your back has a higher temperature (about 37°C) than the stethoscope (probably room temperature, about 20°C) has. This energy is transferred quickly, so the stethoscope feels cold to you.
What is the difference between Temperature & Heat? Heat vs. Temperature Video
Heat vs. Temperature Temperature Degree of Hotness Based on Speed of molecules Heat Quantity of Hotness Based on Speed and Mass
Warm-up (Week 2) 1/20/12 In 3 sentences, write what is happening when your hand touches the table as it relates to HEAT TRANSFER..
Warm-up Activity (Week 2) 1/20/12 Copy the following statements and write True or False 1. Thermal Energy depends partly on the temperature of a substance. 2. A cup of water at 283 K and a pot of water at 283 K have the same thermal energy.
Method #1 Conduction – transfer of thermal energy through matter by direct contact of particles Transfer by Collisions
Conduction can take place in solids, liquids and gases.
Matter must be present for conduction to take place!
Examples: Heating a pan on a stove (pan heats up by conduction) or place a spoon in a bowl of soup (spoon heats up by conduction) The end of this spoon will warm up because conduction, the transfer of energy through direct contact, occurs all the way up the handle.
Method #2 Convection – transfer of thermal energy by bulk movement of matter
Method #2 Transfer by currents
Convection can take place in fluids (materials that flow). Liquids and gases are fluids. Currents carry less dense, warmer material up while cooler, denser material sinks.
Matter must be present for convection to take place!
Examples: Ocean currents, wind, boiling water The repeated rising and sinking of water during boiling are due to convection.
Method #3 Radiation – transfer of thermal energy in the form of waves.
Energy that travels by radiation is often called radiant energy. Only radiant energy that is absorbed changes into thermal energy. Examples: Microwave heating food, sun’s energy heating a sidewalk The coils of this portable heater warm a room partly by radiating visible light and infrared waves.
Different materials absorb radiant energy differently. MaterialEffect Shiny ________________ Dull________________ Dark colors________________ Light colors________________
Different materials absorb radiant energy differently. MaterialEffect Shiny Reflects radiant energy DullAbsorbs radiant energy Dark colorsAbsorbs radiant energy Light colorsReflects radiant energy
Conductor – material with many free electrons that can easily transport kinetic energy. Examples: Metals
Insulator – material that does not allow heat to move easily through it Examples: Wood, plastic, air
The End