Unit 2 – Energy Transfer! Energy: the capacity to do work (the ability to move or change matter); energy has no mass and no volume; it’s intangible; it’s NOT matter. Three types of energy we talk about Kinetic: energy of motion Potential: energy due to position; chemical potential energy is energy stored in bonds and Intermolecular Forces Radiant/Electromagnetic energy (heat and light)  we are mostly concerned with heat

Heat versus Temperature Heat Def: energy due to molecular motion Symbol = Q Units: joules (j) or calories (cal) Measured only when it is used to do work Does work by speeding up the motion of molecules and atoms Flows from hot areas to cold areas Heat is dependent on mass (the more stuff there is, the more energy it can have overall)

Heat versus Temperature Temperature Def: a measure of the average Kinetic Energy (KE) of a substance Symbol = T Units: Kelvin (K) or degrees Celsius (°C) Refers to the intensity of heat in an object Change in T = ΔT = Tf - Ti Temperature is NOT a form of energy Temperature IS a predictor of heat flow from areas of high T to low T Objects can be the same temperature but have different amounts of heat energy

Temperature Scales Sig figs and temperature: because the Celsius temperature scale is a continuum with both positive and negative values, a temperature measurement of 0°C has 1 sig fig (0.1°C = 2 sig figs; 0.98°C = 3 sig figs) 0 K  absolute zero; all molecular motion stops (all atoms condense into one big fuzzy atom) 0 K  theoretical temperature not yet obtained (within a millionth of a degree)

K = °C + 273 °C = K – 273 °F = (9/5*°C) + 32 °C = 5/9* (°F – 32) Conversions K = °C + 273 °C = K – 273 °F = (9/5*°C) + 32 °C = 5/9* (°F – 32) These two will be the most important

Some temperatures you should know off the top of your head… What is happening °C K °F Water melts/freezes 273 32 Water boils/condenses 100 373 212 Especially these!

Try a few! 450 K First to Celsius Equation: °C = K – 273 Calculations: °C = 450 – 273 = 177 °C Then to Fahrenheit Equation: °F = (9/5*°C) + 32 Calculations: °F = (9/5 * 177 °C ) + 32 = 318.6 + 32 = 350.6 °F = 351 °F with sig figs

Try a few! 98.6 °F First to Celsius Equation: °C = 5/9* (°F – 32) Calculations: °C = 5/9* (98.6 – 32) = 5/9*66.6 = 37°C Then to Kelvin Equation: K = °C + 273 Calculations: K = 37 °C + 273 = 310 K

Work together Spend about 5 minutes practicing some of the others on the bottom of p.1 of your notes

Kinetic Molecular Theory * Matter is made up of tiny particles (atoms, molecules) The particles are in constant, random motion Collisions between particles are elastic (all energy stays as motion, none is lost to heat) *the basic principles of KMT are theoretical and begin to break down under certain circumstances  KMT is better at describing matter in high energy states (gases, for example)

States/Phases of matter Shape & volume Distance between molecules Entropy (disorder) Motion of particles Solid Definite shape and volume Small No disorder (particles stay in the same position relative to one another) No random motion (fixed positions) Liquid Indefinite shape and definite volume Much disorder (particles move past each other but continue touching) Some random motion (flowing) Gas Indefinite shape, indefinite volume Large Much disorder (particles move randomly, not touching, only sometimes colliding) Completely random motion (diffusion)

Law of Conservation of Energy within a closed system, energy transforms from one type to another energy is never created nor destroyed  example: electricity lights a bulb: resistance builds up in the tungsten wire, it glows and gives off light and heat; the total energy in the heat and light = energy in the electricity example: when heat is added to water on a hot plate, that heat energy is absorbed by the water molecules, which move faster and faster (increased kinetic energy  higher temperature)

Law of Conservation of Matter matter can also be transformed during chemical and physical changes During these changes, matter is never created or destroyed. example: when ice melts to make water during a phase change, every molecule of H2O in the original ice crystal/cube can be accounted for in the resulting liquid H2O example: when two chemicals are mixed, the atoms may be rearranged to form new chemical compounds, but every original atom can be accounted for in the new substances (on our large scale, we see matter and energy as separate, but matter and energy interconvert at the subatomic level according to Einstein’s Theory of Relativity E = mc2)