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Experiment 7.3A, B: (P.27 - 30)
Comparing the energy
contents (能量值) of different snacks?
Objective: To
compare the energy contents of cookies and peanuts.
Design of Experiment:
(P.29)
Consider of “3Cs” of a fair test (公平測試)
n
Variable
to be changed: Types of snack
n
Variable(s)
to be kept constant保持不變: (Put a “Ö” in the appropriate boxes.)
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Weight
of food
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Ö
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Volume
of water
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Size
of food pieces
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Ö
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Type
of boiling tube
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Ö
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Type
of food
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Ö
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Type
of burning spoon
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Ö
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Initial
(初始)
temperature of water
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Ö
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Others:
distance of the burning snack from the boiling tube
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n
What
to compare: Increase in the temperature of water per
gram of snack
___________________________________________________________________________________
*It is difficult to
obtain different snacks of the same mass (質量) for a fair comparison (公平比較). To solve this problem, we can
measure the weights (重量) of different snacks
used and compare the rise in temperature per gram of food used.
The diagram on right shows the experimental setup實驗裝置:
(P.30)
Procedures:
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1.
Use an electronic balance (電子秤) to measure the weight
of a peanut (花生). Record its weight.
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2. Set up the apparatus as shown on right. Measure the temperature
of the water.
The
temperature of the water is _________oC
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3.
Heat a peanut with a
Bunsen flame as shown.
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4. When the peanut starts
to burn, immediately put it under the boiling tube of water.
5. If the peanut stops
burning, heat it with a Bunsen flame until it burns again and then repeat
step 4.
6. When the peanut is
completely burnt, measure the highest temperature of the water
reached.
The highest temperature of the water is _______________oC.
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7. Repeat steps 1 to 6
using cookies instead of (取代) a peanut.
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Results: (P.30)
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Snack
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Weight of snack used (g)
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Initial water temperature (oC)
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Highest water temperature reached in burning (oC)
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Increase in water temperature* (oC)
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Increase in temperature per gram of snack used# (oC
g-1)
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Peanut
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Wp
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TI
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TH
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TH - TI
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(TH - TI)/
Wp
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Cookies
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Wc
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Ti
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Th
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Th - Ti
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(Th - Ti)/
Wc
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*Increase in
water temperature = Highest water temperature reached – Initial water
temperature
#Increase in
temperature per gram of snack used = 
Discussion:
(P.30)
How
can you compare the energy contents of the snacks?
The greater (greater
/ smaller) the increase in water temperature per gram of snack burnt, the higher
the energy content of the snack.
From the results, the increase in water temperature
per gram of peanut is
higher than that of
cookies.
This shows that peanut has a
higher energy content than cookies.
Conclusion: (P.30)
The
energy content of peanut is higher than that of cookies.
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