Energy and energy transformations Thermodynamics Energy and energy transformations
First Law of Thermodynamics Energy is never created nor destroyed Energy can change forms, but the quantity is always constant.
Second Law of Thermodynamics The Entropy of the Universe is always increasing Entropy= disorder
Third Law of Thermodynamics The entropy of an ideal solid at zero Kelvin is zero All molecular motion stops at 0 K
Heat vs. Temperature
Temperature and Heat Temperature is the measurement of the avg. KE of the molecules in a material. Heat is the transfer of KE from one material to another. Clip
Heat flows from WARMER to COLDER!
How does heat effect temperature? Adding Energy (heat) TO a substance causes its Temperature to go UP! Taking energy (heat) AWAY from a substance causes its - Temperature to go DOWN!
How does heat effect temperature? Adding Energy (heat) TO a substance causes its Temperature to go UP! Taking energy (heat) AWAY from a substance causes its - Temperature to go DOWN!
How does heat effect temperature? Box A : Has more energy (heat) – Has a higher temperature Box B : Has less energy (heat) – Has a lower temperature When they are combined - Box A loses (releases) heat – temperature goes down (= to B) - Box B gains (absorbs) heat – temperature goes up ( = to A)
Heat vs Temperature Temperature - measure of average KE Heat - measure of energy transfer Temp change (∆T) depends on: amount of heat transferred (q) mass of object (m) specific heat of the object (C) Video link: http://www.youtube.com/watch?v=wTi3Hn09OBs&safety_mode=true&persist_safety_mode=1
Specific heat
Have you ever noticed that on a hot summer day the ocean is cooler than the hot sand? Why? The sun has been beating down on both of them for the same amount of time........... Heat (radiation) Heat (radiation) Why aren't they the same temperature? cool hot
It takes MORE thermal energy to raise the temperature of water than the sand! Water has a higher SPECIFIC HEAT that sand!
Specific Heat The amount of energy required to raise the temperature of a material (substance). It takes different amounts of energy to make the same temp change in different substances. We call the amount required: Specific Heat!
Water needs a lot of heat energy before its temperature changes Sand/ cement need a little heat energy before its temperature increases.
Specific Heat Table The lower the specific heat – the easier (faster) it is to heat up and cool down. The higher the specific heat – the harder (slower) it is to heat up and cool down. Which substance would lose its heat fastest? Which substance would take longer to heat up?
Calculating Specific Heat The Greek letter Δ means “change in”
Measuring Heat q = m C ∆T q = heat measured in joules (J) or kilojoules (kJ) 1000J = 1kJ m = mass; measured in grams (g) ∆ T = change in temp measured in Celsius (°C) or Kelvin (K) C = specific heat units are J/g°C or J/gK