Thursday February 21, 2013 Chapter 17: Thermochemistry Calorimeter Enthalpy Heat capacity Heat of combustion Heat of reaction Law of conservation of energy Molar heat of condensation Molar heat of fusion Molar heat of solidification Molar heat of solution Specific heat Standard heat of formation Surroundings System Thermochemistry BRING TEXTBOOK TOMORROW TOO!

Intro to Thermodynamics Wednesday February 17, 2016 EQ: How is specific heat related to conductivity? Intro to Thermodynamics Q Equation ANNOUNCEMENTS:

THERMOCHEMISTRY The study of the changes in heat in chemical reactions and physical processes.

Heat Energy HEAT is the form of energy that flows between 2 objects because of their difference in temperature. Other forms of energy — light electrical kinetic and potential

Heat transfers until thermal equilibrium is established.

Heat Transfer No Change in State Heat = (mass)(specific heat)(change in temperature) Q = mcDT Q: heat (joules) m: mass (grams) c: specific heat (J/goC or J/gK) DT: change in temperature (oC or K)

Specific Heat The amount of heat required to raise the temperature of 1 gram (or 1 kg) of a substance by 1 K (or oC)

Specific Heat

Specific Heat CONDUCTOR? INSULATOR? Is specific heat capacity related to heat conductivity? Iron Wood Air Aluminum Water https://www.youtube.com/watch?v=-wj2Oh50wsA

Practice Problem #1 A 15.75-g piece of iron is heated and as a result its temperature changes from 25°C to 175°C. Calculate the amount of heat absorbed by the iron.

Practice Problem #2 How much energy would be absorbed by 550 g of silver that is heated from 24oC to 45oC? (The specific heat of silver is 235 J/kgK)

Practice #3 25.0 g of mercury is heated from 25°C to 155°C, and absorbs 455 joules of heat in the process. Calculate the specific heat capacity of mercury.

Thursday February 18, 2016 Energy In a Cheeto Lab EQ: How much energy is stored in a cheeto? How are food calories related to heat energy? Energy In a Cheeto Lab ANNOUNCEMENTS:

Heat Transfer No Change in State Heat = (mass)(specific heat)(change in temperature) Q = mcDT Q: heat (joules) m: mass (grams) c: specific heat (J/goC or J/gK) DT: change in temperature (oC or K)

Which has more Calories? Crunchy or Puffy Cheetos All human activity requires “burning” food for energy. How much energy is released when food burns in the body? How is the caloric content of food determined? Lets investigate the caloric content of a popular snack food, Cheetos.

Lab Setup Safety Precautions Wear Goggles Tie back loose hair and sleeves No phone cords or headphones in lab No eating

Ticket Out the Door

1 gram of water has a volume of 1 mL. Hint for #7 1 gram of water has a volume of 1 mL.

Specific Heat Practice WS Part 2 0.46 J/gC or 460 J/kgC 0.14 J/gC or 140 J/kgC 32oC 0.131 J/gC or 131 J/kgC 1540 g 7600 J 14000 J

HOMEWORK Complete the back Due tomorrow

Friday March 14, 2014 Define specific heat. The amount of energy required to raise 1 kg of a substance by 1 Kelvin. Put your vocabulary in the tray at this time!

Specific Heat The amount of heat required to raise the temperature of 1 gram (or 1 kg) of a substance by 1 K (or oC)

Lab Setup: Use about 20 mL of water 1 calorie = 4.184 Joules All are units of heat energy. 1 calorie = 4.184 Joules Specific heat of water in calories: 1.00 cal/gC 1 food Calorie = 1000 calories Lab Setup: Use about 20 mL of water

Please sit according to your lab station from Friday. Stations 3 and 4 Stations 5 and 6 Stations 1 and 2

How are the “joule”, “calorie”, and “Calorie” related? Monday March 17, 2014 Warmup Question: How are the “joule”, “calorie”, and “Calorie” related? All are units of heat energy. 1 calorie = 4.184 Joules Specific heat of water in calories: 1.00 cal/gC 1 food Calorie = 1000 calories

Lab Calculations

Today Exchange data with the other group. Use your data to make to make the calculations on the back. Turn in. Work on Heat Calculations WS

Cheeto lab due at this time!!! Tuesday March 18, 2014 How much energy would be absorbed by 550 g of silver that is heated from 24oC to 45oC? (The specific heat of silver is 235 J/kgK) Cheeto lab due at this time!!!

Heat of Fusion & Heat of Vaporization

Wednesday February 25, 2015 Last Call: Cheeto Lab Heat Calculations WS EQ: How much energy is stored in a cheeto? How are food calories related to heat energy? Last Call: Cheeto Lab Heat Calculations WS ANNOUNCEMENTS:

Heat of Fusion/Heat of Vaporization Thursday February 26, 2015 EQ: What is difference between heat of fusion and heat of vaporization? Review phase change Heat of Fusion/Heat of Vaporization ANNOUNCEMENTS:

PHASE CHANGE liquid gas solid Energy Increases!

PHASE CHANGES Freezing liquid to solid Energy released Melting Solid to liquid Energy absorbed Freezing liquid to solid Energy released

Evaporation or Vaporization Liquid to gas Energy absorbed Condensation Gas to liquid Energy released

Sublimation Solid to gas

Deposition gas to solid http://www.youtube.com/watch?v=Hsu3JoXN-qU

A,C,E: temperature changes; phase is constant B,D: temperature is constant; phase changes

Heat Transfer with Change of State Solid Liquid Heat Transferred = (heat of fusion)(mass) Q = (DHfus)(m) Example: Ice + 334 J/g (heat of fusion) -----> Liquid water

Heat Transfer with Change of State Liquid Gas Heat Transferred = (heat of vaporization)(mass) Q = (DHvap)(m) Example: Water + 2260 J/g (heat of vaporization) -----> Steam

Which Q equation?? No Phase Change Phase change Q = mcDT solid/liquid: Q = (DHfus)(m) liquid/gas: Q = (DHvap)(m) For water: c = 4.18 J/gC DHfus = 334 J/g DHvap = 2260 J/g

Friday February 26, 2015 Kahoot: Which Q is it? Go over Parts 1 and 2 EQ: What is difference between heat of fusion and heat of vaporization? Kahoot: Which Q is it? Go over Parts 1 and 2 Complete Part 3 ANNOUNCEMENTS:

Friday February 26, 2015 Kahoot: Which Q is it? Go over Parts 1 and 2 EQ: What is difference between heat of fusion and heat of vaporization? Kahoot: Which Q is it? Go over Parts 1 and 2 Complete Part 3 ANNOUNCEMENTS:

Complete Heat Calculations WS. Check your answers with the key. Work Session Complete Heat Calculations WS. Check your answers with the key. Hint: Be sure all of your units are in sync before you solve!

Q=mcDT Q=DHvap(m) Q=mcDT Q=DHfus(m) Q=mcDT

Thursday March 20, 2014 A student uses the Q=mcDT equation to figure out how much heat is gained by a piece of ice as it melts into liquid. Why is this incorrect? The equation Q=mcDT cannot be used for a substance undergoing a phase change, only while it is in one specific phase because temperature does not change in a phase change.

Which Q equation?? No Phase Change Phase change Q = mcDT solid/liquid: Q = (DHfus)(m) liquid/gas: Q = (DHvap)(m) For water: c = 4.186 J/gC; DHfus = 334 J/g; DHvap = 2260 J/g

Total Q partner activity Tuesday March 3, 2015 EQ: What is difference between heat of fusion and heat of vaporization? Calculating Total Q Quiz Total Q partner activity ANNOUNCEMENTS:

Total Heat Calculations How much heat is required to raise 250.0 g of ice at a temperature of -15oC to room temperature of 21.0oC?

Q=mcDT Q=DHvap(m) Q=mcDT Q=DHfus(m) Q=mcDT

HEAT EQUATIONS Q = mcDT Q = (DHfus)(m) Q = (DHvap)(m) For water: c = 4.186 J/gC; DHfus = 334 J/g; DHvap = 2260 J/g For ice: c = 2.06 J/g; For steam (gas): c = 2.02 J/g

TOTAL Q ASSIGNMENT With your partner: Draw a sketch of the phase change graph and label the START and STOP points for your problems. List the equations you would use to solve each step the problem. Solve the heat for each step. Find the total Q.