Heat

Kinetic-Molecular Theory All molecules have kinetic energy at all times Molecules collide with each other randomly and elastically. Faster molecules will collide with more energy, causing more pressure, and will spread out if possible.

Internal energy Temperature Equal to the total energy of all of its particles Depends on the size of the sample Proportional to its temperature Temperature Temperature: the average kinetic energy of an object’s molecules Higher temperature means faster molecules. Hotter objects will spread out more and expand. The pressure changes if it cannot spread out.

Temperature Scales/Conversions Units: Kelvin (K) or Degrees Celsius (°C). Scale Ice point Steam Point Fahrenheit 32oF 212oF Celsius 0oC 100oC Kelvin 273.15K 373.15K

Heat Heat: Energy transfer between objects of different temperature Heat always flows from higher temperatures to lower temperatures

Heat & Energy Loss When energy is lost from a system, it transforms into Heat. Examples: When friction causes a sliding object to slow down or stop, the kinetic energy turns into heat. When a clay ball is thrown at a wall, the kinetic energy turns into heat that increases the temperature of the clay. When electrons move through a resistor, the electrical energy turns into heat. A machine loses efficiency in each process as mechanical energy is lost as heat to the surroundings. This is the most important slide for the entire unit!!!

Thermal Equilibrium Thermal Equilibrium: No thermal energy transfers between objects in contact. No heat transfer Objects have the same average kinetic energy (same Temperature) Hotter objects will transfer heat to cooler objects until the objects reach thermal equilibrium.

Thermal Expansion When an object’s temperature increases, it will expand. Metals expand more than other solids.