Experiement A: Calorimetry Flashcards
Objectives (2)
Determine the heat capacity of a metal object and a liquid (2-PrOH)
Determine the enthalpy of fusion of ice
What is an intensive property
Doesn’t depend on the mass of the substance or system
What is an extensive property
Does depend on the mass of the substance or system
Is heat capacity extensive or intensive
Extensive
What is heat capacity, measured in, and variable
Amount of energy needed to chance an objects temp by one degree
J/Celsius
A system contains ____ ____energy (not heat or work)
Internal energy
In calorimetry energy is transferred due to a ___ change
Temp
What is heat and what variable represents it
Energy in transition
q
What formula for C relates heat and temp
C = q/(Tf-Ti)
What formula for C relates specific heat capacity to mass of a substance
And when do you use this
C = c(mass of substance)
When substance is known
Are specific heat capacity and mass extensive or intensive
Intensive
What is specific heat capacity measured in
c
What formula relates molar heat capacity to moles of substance
And when do you use this
C = Cm(moles of substance)
What is Cm
Molar heat capacity
Are Cm and moles extensive or intensive properties
Intensive
Is the calorimeter is at constant pressure and why
Yes
It’s open to the atmosphere
What is the definition of triangle H, what does it represent, units
Energy transferred that entrees or leaves the system
Enthalpy change
J/mol
What does endothermic mean
Energy transferred to the system from surroundings
(+) triangle H
(-) triangle H
Endo or exo for each?
(+) endothermic
(-) exothermic
How are enthalpy change and temp related
Triangle H = heat (at constant pressure)
How does heat capacity relate enthalpy change and temp
C = triangle H/ (Tf-Ti)
During the experiment why does the total enthalpy change = 0
(Total enthalpy of calorimeter)
+ (it’s contents) = 0
Part 1: heat capacity
Explain the three steps
1) calorimeter holds room temp water
2) metal block will be heated in a boiling water bath
3) when metal block is transferred to calorimeter, block will LOSE heat to water and calorimeter, temp of calorimeter water increases
How does total enthalpy change relate enthalpy change of the block and enthalpy change of the water
Triangle H total = triangle H block
+ triangle H water = 0
So,
Triangle H block = -(triangle H water)
How does the heat capacity of the block relate the heat capacity of water, and the temp of water and the block
C block = (-C water(Tf-Ti)water)/
(Tf-Ti) block
Formula for heat capacity of water
(Mass of water)(c)
Formula for mass of water
(Volume added)(density of water at room temp)
How does specific heat capacity of the block relate the heat capacity of the block and the mass of the block
c block = C block/ mass of block
Part 2: enthalpy fusion of ice
Explain the objective and the one step
Estimate the enthalpy fusion of ice for H20(s) —-> H2O(l)
Ice at 0 degrees (melting point of ice) is added to calorimeter water at room temp, ice melts, water cools to Tf, water from melted ice warms from 0 degrees to Tf
What does fusion mean
Melting
How does triangle H water relate triangle H fusion and triangle H ice water
-triangle H water = triangle fusion + triangle H ice water
How is the calorimeter built
- 2 polystyrene cups one side the other
- insert thermometer through the smaller of the two holes at the top
-black plastic sleeve on top holds tip of thermometer approx 1 cm away from bottom when lid is put into cups
The measured max temp of calorimeter is less than ___
Because some energy enters/leaves calorimeter during reactions
Ideal
After max temp is reached, temp will change back with time towards ___
Ti
