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Thermochemistry through specific heat
HW: WS #1
q = mcΔT
CW: WS#2
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Holiday! Calorimetry and enthalpy
HW: WS#3
Chapter 11 Major Grade Lab
Part I: Calorimetry
Chapter 11 Major Grade Lab
Part II: Heat of Reaction of MgCl2
Write up due 1/29
Complete Ch 11 notes
HW: WS#4, Formal Lab Write up
28 29 30 31 February 1
Phase Change Lab (Due 1/30)
HW: Formal Lab Write up
Chapter 11 Review
HW: Phase Change lab, STUDY
Chapter
11 TEST
Thermochemistry- Chapter 11
11.1 Thermochemistry• Thermochemistry- is concerned with the _____________________ that occur during chemical reactions.
• Energy – The capacity ________________________________. It comes in many forms. • _______________ Energy: motion of particles
• _______________ Energy: stored energy
A student is heating water to cook pasta. She notices it begins to boil at 100°C. What is the temperature of the water if she keeps boiling it for 15 more minutes?
For EXAMPLE: When gasoline burns, the potential energy stored in its chemical bonds is released as KE to do work, such as moving car.
• Heat (q)- energy that transfers from one object to another because of a ______________ ____________________. Heat always flows from a ________ object to a ________ object. • System – the part of the universe on which you focus your attention
• Surroundings– everything else in the universe
• Law of Conservation of Energy – in any chemical or physical process, energy is neither _______________________________________.
Write potential or kinetic beside each of the following. A stretched rubber band___________
A cookie ________
For EXAMPLE: Heat may be lost by the system, but it is not destroyed. It is transferred to the surroundings.
• Endothermic process- system ______________ heat from the surroundings • Exothermic process – system _______________ heat to the surroundings • Endothermic or Exothermicprocess?
– Evaporating alcohol: __________________ – Leaves burning: ________________
– Boiling water: ___________________ – Water cooling: _________________ – Melting ice: _________________ – Freezing water: ___________________ • Energy units: ______________________________
• Calorie – quantity of heat needed to raise the temperature of ________________________ • A food Calorie is used in nutrition and is capitalized.
• 1 Calorie = ___________ cal = ________ kcal
What are endothermic and exothermic processes?
1. If a label on a candy bar indicated it contains 180 Calories, that is really 180 kcal, or 180,000 calories! If “burned” the sugar and fat in the candy bar release 180,000 cal of energy.
• Heat capacity- amount of heat needed to increase the temperature of an object 1oC. It depends on
________________________________________.
For EXAMPLE: It takes more heat to increase the temperature of a large pot of water than a small cup of water. It takes more heat to raise the temperature of water than metal.
• Specific Heat (C)- the amount of heat it takes to raise the temperature of 1g of substance 1oC. It
can be calculated:
What has a higher heat capacity, water or Al metal? Explain your answer.
What is the formula to calculate heat energy?
• C = q (cal or J) [mass (g)][T(°C)]
• Specific heat units ________________
• A high specific heat is matter that loses or gains heat slowly (water)
• Water has a uniquely ___________ specific heat compared to other substances.
• To calculate the heat energy required for a temperature change, use the following formula: ________________________
– q = _____________ – m = ____________
– C= __________________________ – ∆T = ______________________________
2. How much energy is required to heat an iron nail with a mass of 7.0g from 25oC until it becomes
red hot at 750oC? equation: q = mC∆T
First, __________________________________.
3. If 5750 J of energy is added to a 455g piece of glass at 24.0ºC, what is the final temperature of the glass?
4. A 30.0g sample of an unknown metal is heated from 22.0 ºC to 59.2 ºC. During the process, 1.00 KJ of energy is absorbed by the metal. What is the specific heat of the metal?
11.2 Calorimetry - the measurement of heat change for chemical and physical processes. • Heat released by system = _______________ by surroundings
• _________________________- insulated device used to measure the absorption or release heat in a chemical or physical process.
• A bomb calorimeter is used to measure heat at a constant volume
6. A 25g sample of a metal at 75.0 ºC is placed in a calorimeter containing 25g of H2O at 20 ºC.
The temperature stopped changing at 29.4 ºC. What is the specific heat of the metal? 2 Steps to solve:
1. Find the q value for the water
2. Use the value from step one to find the C value of the metal.
You will have 2 sets of givens. Remember the final temperature and energy for both will be the same.
qwater = mC(Tf-Ti) qmetal = mC(Tf-Ti)
qwater = (45gH2O)(4.18J/g°C)(6.4°C) 1203.84J = (25g)(C)(75.0°-29.4°) qwater = 1203.84J Cmetal = 1.1J/g°C
qwater = qmetal
What is calorimetry, in your own words?
7. A 25g sample of a metal at 75.0 ºC is placed in a calorimeter containing 25g of H2O at 20 ºC.
Enthalpy
Enthalpy (H) is the amount of _________________________________________________. Enthalpy Change: (same as energy) ______________________________________
Exothermic reaction has ______ Endothermic reaction has ___________ ______________________ equation includes heat changes.
Physical state must be included!!!
– CH4(g) + 2O2(g) à CO2(g) + 2H2O(g) + 890KJ
• ∆H= -890 kJ
• Exothermic (__________________________) – 2H20 + 241.8 KJ à 2H2(g) + O2(g)
• ∆H= 241.8 kJ
• _______________________ (energy absorbed)
– CH4(g) + 2O2(g) à
• Exothermic – energy is a ____________________ • Endothermic – energy is a ___________________ • ∆H is also called the _______________________.
11. 3 Heat in Change of State
The specific heat of water is 1.0cal/gºC The specific heat ice and steam is 0.5cal/gºC
q = mc∆T
Heat of ______________ - heat required to melt 1 gram of solid Heat of _____________________ - heat released as 1 gram of liquid freezes
Heat of fusion of water = ____________________ = heat of solidification
q = mHf
How many joules of energy would it take to melt 23 mol water?
Heat of vaporization- heat required to vaporize ________________________________ Heat of _______________________- heat released as 1 gram of a gas condenses to a liquid. Heat of vaporization for water = __________________ = Heat of Condensation
q = mHv
*Temperature is constant during a phase change
Which value is higher, the heat of fusion or the heat of vaporization?
Why is the slope between ice and vapor so long on the heating curve?
Heating/Cooling Curve shows energy changes. All matter follows curve when energy is added or lost.
• Horizontal portions of curve indicate a physical state change. Notice ___________ _______________________________. However, there is a change in particle position resulting in a _________________________________________.
• Slope portions show _________________________ which indicates a __________ ________________________ as well.
8. How much heat, in calories, is needed to melt 150g of ice at 0 ºC?
9. How much heat, in calories, is needed to heat the liquid water in the above problem to 20. ºC?
11. How many calories are released when 36g of steam at 100 ºC condenses to water at 100 ºC?
12. How many calories are needed to convert 5.0g of ice at -15ºC to steam at 130ºC? (five problems)
11. 4 Standard Heat of Formation
• Standard heat of _____________________ of a compound (∆Hfº)
• ∆Hfº of a free element in its _____________________ is zero.
• This is another way to calculate ∆H for a reaction.
• ∆H =______________________________-use table of “Standard Heats of Formation”.
What is the formula for standard heat of formation?
13. Calculate ∆H for the following reaction: CaCO3(s) à CaO(s) + CO2(g)
*First, make sure equations are balanced. *You will multiply the ∆H by the coefficient.
(all coefficients for this problem are 1, so do not need to worry about that)