Extra Credit for Calorimetry Lab Report
Extra credit question : The procedure used to direct the student to blot the object dry before placing it in the calorimeter. Instead of blotting dry, an alternate method is to shake the object quickly while transferring directly to the calorimeter cup. Shaking: During the transfer to the calorimeter, assume shaking leaves 4 drops of hot water (at T
Cu cylinder (with no heat transfer to environment; no change in T h h
) on a 60 gram
). Assume 1 g of water is equivalent to 1 cc = 1 ml ≈ 20 drops. Blotting: During the blotting process, assume no hot water remains; and the Cu cylinder cools off by about 4°C during this drying/blotting process. Assume T h
– T eq
= 75 C°.
Given the conditions above, which of the above two situations contribute to the greatest error? To answer this question, calculate the percent change in specific heat of the copper between what you would theoretically get with no error and with error.
Do this for both transfer methods. Make sure you identify whether the transfer method gives a specific heat value greater than it should be or less than it should be . DO NOT use your data values to answer this question … it can be answered with the information given above and the formula hints given below (unknown variables cancel out if you do the math correctly). Show your work to receive credit.
c s
= specific heat value without error due to transfer method c serr
= specific heat value with error due to transfer method
Percent change = [( c
Q = cm Δ T serr
- c s
)/ c s
] x 100 (%)
Without transfer method error: Q sample
= Q calorimeter
Heat lost by the sample = Heat gained by the water and the calorimeter m s which gives c s
( T h
– T eq
) = ( m w c w
+ m c c c
) ( T eq
– T c
) c s
= [( m w c w
+ m c c c
) ( T eq
– T c
)]/[ m s
( T h
– T eq
)]
Shaking : Q drops
+ Q sample
= Q calorimeter
(Use the accepted value of specific heat for c
Heat lost by water drops and sample = heat gain by calorimeter
Blotting : Q sample
= Q calorimeter s
in percent change calculation)
but the temperature change in the sample is [( T h
– 4 C°) –
(Use without error formula with variables for c s
in percent change calculation – most
T eq
] variables cancel out)
Question: Now that you have done the math, which transfer method is the best (causes least error)?
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Bonus extra credit question (you must answer extra credit question to get credit for this one):
At what change in temperature of the sample, Δ T = ( T h
– T eq
), do the shaking and blotting transfer methods give the same percent change (absolute value)? Show work.
Lab: Calorimetry Updated 5/19/16