Week 2:  Heat, Temperature, Heat Transfer, Energy, Work

    Heat: vibration of atoms or molecules.  the faster the atoms vibrate, the more heat present

            heat is a kind of energy, often called thermal energy.  see below

      heat has a special property: it quickly spreads out, going from concentrated to diffuse

            example:  a bathtub of hot water cools down quickly and heats up the bathroom

      metric units of heat:  the calorie (little c).  the Calorie (big C) = 1000 calories (little c’s)

            1 calorie = heat needed to raise the temperature of 1 gram of water by 1° Celsius

      English units of heat:  the British Thermal Unit or BTU.

         there are approximately 140,000 BTU in one gallon of home heating oil

    Temperature:  a way of comparing the heat in two objects.  not dependent on mass

      if two objects have the same amount of heat, they have the same temperature

            example:  body temperature of Hull and Shaquille O’Neal = approximately 99°F

            both humans have same temperature, even though they have different masses

      Farenheit scale of temperature:  32°F = freezing water, 212°F = boiling water

      Celsius scale of temperature:  0°C = freezing water, 100°C = boiling water

      Kelvin scale of temperature:  273°K = freezing water, 373°K = boiling water

 

    Heat Capacity:  the ability of an object/mass to absorb heat OR the resistance to change in T

      water has a very high heat capacity, it takes a lot of heat to change water’s temperature by 1°

            water: most bizarre substance on Planet Earth. oceans are a big heat sink.

      steel has a very low heat capacity, a little heat will change steel’s temperature          

     

    Heat Transfer:  heat is a type of energy that transfers very easily from one place to another

      three different ways that heat moves from place to place.

            Conduction:  heat transferred from hot object to cold object by physical contact

                  ex:  put your cold hands around a hot cup of cocoa, heat exchanged by contact

                        vibration of cocoa molecules transferred to your hand

                  good conductor transfers heat easily (metals), poor conductors are good insulators (ceramics)

            Convection:  heat transferred by moving hot matter to a cold place

                  ex:  “blob” of hot air rises to ceiling.  very common in atmosphere and Earth’s interior

            Radiation:  heat transferred by electromagnetic waves (aka radiation)

                  ex:  Sun produces EM waves, absorbed by Earth's atmosphere and surface

                  most radiation is invisible; can also travel through space in absence of matter

      all 3 can be active at same time:  open the door of a hot oven and you get all three in the kitchen

 

    Energy:  the ability or the capacity to do work.  work is one possible result or outcome of energy

      work = force times the distance over which the force acts (work = force times distance = F x d)

            ex:  push your stalled car 1 block down the street = work = force (push) x distance (1 block)

      metric unit of work/energy:  1 Joule (J) = one Newton of force (N, Nt) times one meter (m)

              1 calorie = 4.2 Joules

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