Using Scratch to Calculate Heat Loss and Temperature Change for a Home – Part 2
Purpose:
 To use recursion to calculate the heat loss and temperature
change in a house over a 12 hour period
Materials Required
 Scratch programming environment and a computer on which it
runs
Procedure
 Open Scratch and open the program that was used to calculate the heat loss and temperature
drop over a 30 minute period.
 Insert a Repeat Control block in the program to perform that calculation 24 times.
o Separate the program into three parts by dragging blocks away from the main script
(but still leaving them in the script area.) First drag away the “stop script” block, then
the three blocks that actually do the heat loss and temperature calculations.
o From the Control area, drag a Repeat block onto the bottom of the script, just under
where you set the initial values for the model parameters. Allow it to snap into place.
Change the value of “Repeat” from 10 to 24.
o From the Control area, drag a “Wait 1 Seconds” block into the Repeat block. The repeat
block will surround this statement on the top, bottom, and left side.
o Drag the three blocks (two set and one change) into the Repeat block.
o Drag the “stop script” to below the repeat block.
 Set the parameters in the initialization script (activated by the spacebar) to that of one of the
homes from the prior activity.
 Run the script by clicking on the spacebar to initialize the model, then on the flag; observe the
temperature fall over time. You may wish to adjust the Wait time.
 Record the indoor temperature in the table below
Iteration Temperature
Iteration
Temperature
Iteration
Temperature
0 (start)
9
17
1
10
18
2
11
19
3
12
20
4
13
21
5
14
22
6
15
23
7
16
24
8
Analysis and Discussion
Indoor Temperature (° C)
Plot the data on the graph below:
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Iteration
The axes are labeled for each iteration. Under the axes, label the iteration number corresponding to 3
hours, 6 hours, 9 hours, and 12 hours.
What is the shape of the graph? Is it a line or a curve (use a straight edge to check)? If a curve, is it
getting more or less steep as time goes on?
Use what you know about what governs heat loss to explain the shape of the curve.
Describe how the shape would change if the heat loss was greater because the R-value was lowered.
Describe how the shape would change if the heat capacity of the inside of the home was increased.
Rubric
Stellar
Well Done
OK
Missed the mark
Experiment
Records data as taken,
data table is neat,
units are observed,
care is taken
Data is sloppily
recorded, readings are
done casually/quickly
Data is missing or
approximated
Data Analysis
Calculations are done
neatly and accurately
and with appropriate
significant figures
Discussion
Answers are in full
sentences, show
understanding of the
concept of specific
heat, show
understanding of
relevance to a home.
Calculations are done
accurately and are
either not neat or have
incorrect number of
significant figures
Answers show
understanding of the
concept of specific
heat, some
understanding of
relevance to a home.
Data obtained, but due
care is not seen. Top
cup is slightly off, not
monitoring
temperature rise, etc.
Calculations require
correction or
instructions not
followed.
Very brief answers
that echo material
presented, marginally
neat, some relevance
to a home.
Answers are missing or
so short as to provide
no insight into the
understanding by the
student.
Calculations are
incorrect because
procedure was not
followed.