Heat, energy and energy transfer Flashcards
define heat
a form of energy measured in joules
difference between heat and temperature
adding heat will cause temperature to rise
3 effects of adding and removing heat energy
increases temperature
causes expansion of material vs contraction
changes state of a substance (solid-liquid-gas)
show that solids expand when heat energy is added
a metal ball on a skewer, a ring with the same diameter as the metal ball. Heat the metal ball over the bunsen burner, it won’t fit through the ring. Cool it down in water, it will fit.
show that liquids expand when heat energy is added
how is this principle used in life
a beaker with water on a stand over a bunsen burner. a conical flask inside the beaker with alcohol, and a glass tube coming up from the conical flask. As the water heats, the level of alcohol in the glass tube will rise because it has expanded.
thermometers with alcohol or mercury use this
how is water different
it expands when it freezes - makes water pipes burst
show that gases expand when heated and contract when cooled
beaker with water on bottom. Conical flask upside down above beaker, with glass tube coming out of it into the water. heat the conical flask from the outside with a bunsen burner- bubbles should be seen. As it cools down, the glass tube will suck up water because the air inside is contracting.
what are the 3 ways heat energy moves from a warm place to a cool place?
conduction, convection, radiation
define conduction
the movement of heat energy through a substance without any overall movement of the substance itself
investigate the rate of conduction through various materials
add hot water to a tank. on the other side of the tank, attach equal lengths of materials of the same diameter. with vaseline, stick a tack on each one. The first tack to fall off bc the vaseline melted is the best conductor of heat - copper.
define convection
the movement of heat energy through liquids and gases due to the motion of the substance itself
investigate convection in liquids
conical flask with a lid on top. a little bit of dye on the bottom and some water. over a stand on a bunsen burner . as it heats up, the convection currents can be seen as the hot water moves up and colder water sinks down the sides.
How are convection currents involved in global warming?
cause the north atlantic drift which keeps seawater near ireland warm and prevents harsh winters. however it will reverse if global warming happens
-causes wind. if wind is warmed, violent storms will result
investigate convection in gases
a box with two chimneys on right and left. candle at bottom heats air, risinf out og right chimney. cool air comes down left chimney-convection currents can be seen with smoke from a piece of smouldering string held down the left chimney
define radiation
the transfer of heat energy via radiation waves that can travel through a vacuum.
