UNIT 3: ENERGY

Aim # 1- what is the relationship between energy and temperature? What is Energy? The ability to do work or produce heat Forms of energy: Light (radio waves, microwaves) , electrical, ,magnetic, chemical, mechanical, nuclear

Temperature Temperature is the average kinetic energy of a substance Temperature measure how fast particles are moving *** Not a form of heat, it is a measurement of heat**** Thermometers use two fixed points, the boiling point and freezing point of water BP = 100 ⁰ C (373 K) FP and MP = 0 ⁰ C (273 K) (Absolute Zero is 0 Kelvin )

Aim # 2 how can we use temp scales to convert to different units? K= ⁰C + 273 ***All motion stops at Absolute zero Try the temperature conversions in your note packet

Temperature and heat The flow of energy due to temperature difference, heat will flow from higher temperature to lower temperature Heat is the total kinetic energy of a substance (q) q is the unit for the quantity of heat involved in a physical or chemical change This heat comes from bonds breaking and new bonds formed in a chemical reaction “BARF”

Potential energy (PE) is the energy in position, stored energy Aim # 3 how does energy aid in chemical reactions? Potential and Kinetic energy Potential energy (PE) is the energy in position, stored energy ball at the top of a hill, chemical bonds (attachments) between atoms of a substance

Kinetic energy (KE) is energy in motion A certain amount of energy is required to START a chemical reaction- activation energy Once started all chemical changes involve another energy change Physical changes do NOT always involve energy change Types of energy change are exothermic or endothermic

Exothermic- “exit” Energy is released, given off, “feels” hot Chemical Change Example: metal and an acid reaction Physical Change Water freezing

Energy is absorbed, taken in, put in Chemical Change- will feel “cold” Endothermic – “IN” Energy is absorbed, taken in, put in Chemical Change- will feel “cold” Ba (OH)2 + NH4Cl Physical change- energy is put in Boiling water

AIM # 4 – HOW DO WE CALCULATE SPECIFIC HEAT? Calculating heat Units of heat Calorie- amount of heat required to raise the temperature of 1 gram of water 1⁰ C Joule – SI unit of heat 1 calorie = 4.18 Joules Heat equation Heat= mass x specific heat capacity x change in temperature q= m c t T= t f - ti

Specific heat Specific heat capacity is the amount of heat required to raise the temperature of 1 gram of a substance 1 ⁰ C For water C= 4.18 J/g ⁰ C Example # 1 : How much heat is required to raise the temperature of 20.0 grams of water from 10.0 ⁰ C to 40.0 ⁰ C

HEAT CALCULATION PRACTICE

HEAT CALCULATION PRACTICE

AIM # 3: How can we represent/calculate the energy associated with phase changes? Reference Table has the equations! (Table T)

HEATING/COOLING CURVES Time

HEAT OF FUSION Amount of heat needed to melt a solid under normal conditions Freezing requires same amount of heat as melting Heat lost in freezing = heat gained in melting Hf = 334 J/g Table T for equation: q = mHf

HEAT OF VAPORIZATION Amount of heat needed to convert a liquid to gas under normal conditions Condensation requires same amount of heat as vaporization Heat lost in condensing steam = heat gained in boiling water Hv = 2,260 J/g Table T for equation :q = mHv

Energy Changes Associated with Phase Changes – Heat Formulas Heat of Fusion (q=mHf) : Clues to use this formula would be the following words- melting, freezing, solidification, crystallization, solid to liquid, liquid to solid (this value for water is located on Reference Table B) Heat of Vaporization (q=mHv) : : Clues to use this formula would be the following words – evaporation, vaporization, condensation, liquid to gas, gas to liquid, steam (this value for water is located on Reference Table B)   Anytime there is a temperature change (a substance cooling or being heated) you would use the q=mcΔT Where ΔT = Tfinal – Tinitial

Calorimetry A calorimeter is used to measure the heat absorbed or released in a chemical process by measuring the temperature change of an insulated mass of water https://www.youtube.com/wat ch?v=EAgbknIDKNo