What are the states of Matter? Solid Lowest energy/heat Molecules barely moving Definite, uniform shape Example: ice
States of Matter Liquid Medium energy/heat Molecules slowly moving Shape of container Example: water
States of Matter Gas High energy Molecules moving rapidly and bouncing Example: air in a balloon
http://ds9.ssl.berkeley.edu/lws_gems/2/part2.htm UC Regents
What is a Phase Change? Phase Change when a substance changes from one state to another Phase changes occur when you add or subtract energy from a system. When energy is added, it is used to heat the substance, then it is used to change the substance into a different state. (temp doesn t change during Examples: Solid liquid Liquid gas
Phase Changes Vaporization: Liquid Condensation: Gas Freezing: Liquid Sublimation: Solid Deposition: Gas Gas (water boiling) Liquid (dew on grass in morning) Solid (ice cubes) Gas (dry ice) Solid (frost in winter) Melting: Solid Liquid (candle)
Phase Changes GAS Sublimation Deposition Evaporation Condensation Melting SOLID Freezing LIQUID
The phase diagram is graph of pressure vs. temperature that shows conditions under which the phases of a substance exits: http://itl.chem.ufl.edu/4411/2041/lec_f.html
Phase Diagram for Water http://www.chem.uidaho.edu/~honors/phases.html
Triple Point: The lower point is called the "triple point" and is the unique combination of temperature and pressure at which all three phases exist simultaneously.
Heating/Cooling Curve Heat of Vaporization Heat of Fusion/Crystallization Energy is added as Heat
Changes in Matter and Energy Matter cannot be created or destroyed. But it can be changed and when it does, that is how we get energy! Energy - capacity to do work or produce heat Energy is always involved in physical and chemical changes. Energy can take several forms: Heat, light, (sound, chemical, electrical) Measured in calories, Calories (kcal), and joules
Law of Conservation of Energy: energy can be absorbed or released, but it cannot be created or destroyed through ordinary chemical reactions. Energy can be transferred.
Kinetic and Potential Energy Kinetic energy: is the energy of motion. Potential Energy: energy of Position Stored energy (chemical bonds)
Since energy is constant and cannot be created or destroyed. Total Energy = KE + PE Temperature: kinetic energy of all particles within matter. There are times during phase changes when temperature does not change, but stays constant while the energy works to change the phase (ie: the heating curve of water)
Heating/Cooling Curve Heat of Vaporization Heat of Fusion Energy is added as Heat
Exothermic energy is released by the substance into the surroundings less PE, more KE, so temperature rises Ex: a match burning Endothermic energy is absorbed by the substance from the surroundings more PE, less KE, so temperature drops Ex: water freezing
Energy Calorie (cal): the amount of energy (heat) required to raise the temperature of one gram of water by one Celcius degree Standard unit for energy is the joule (J) 1 cal = 4.184 J 60.1 cal x 4.184 J = 251 J 1 cal Specific Heat (s) : amount of energy required to change the temperature of one gram of a substance 1 o C Varies from one substance to another Heat always travels from high concentration to low concentration!! Heat lost = Heat gained
Water has a specific heat = 1 cal/g o C or 4.184 J/g o C Water has the second highest specific heat capacity of all known substances. So it requires high amounts of heat energy to raise water temperature. water also has a high energy/heat requirement for evaporation S IRON = 0.449 J/g o C Which would heat up faster, 5.00 grams of iron or 5.00 grams of water? Which would cool down faster, 5.00 grams of iron or 5.00 grams of water? Which is a better thermal conductor? Which is a better insulator?
Q = s x m x ΔT Q = energy (heat) required (J) or (cal) s = specific heat capacity (J/g o C) or (cal/g o C) m = mass of the sample in grams ΔT = change in temperature in o C A 2.8 g sample of a pure metal requires 10.1 J of energy to change its temperature from 21 o C to 36 o C. What is the specific heat of the metal? s = Q = 10.1 J = 0.24 J/g o C m x ΔT (2.8 g x 15 o C)