Question 9
Helen wanted to find out how the area of exposed surface affects the rate of
evaporation. She got five identical towels and prepared five set-ups as shown
in the table below.
Variable
Set-up
A
B
C
D
E
Amount of water poured
onto the towel
30 ml
20 ml
30 ml
20 ml
30 ml
Number of times towel
was folded
2
3
2
2
3
Presence of a fan
Yes
Yes
No
Yes
No
Surrounding temperature
30 oC
30 oC
10 oC
30 oC
30 oC
Which two set-ups should she use to ensure that her experiment was fair?
A. A and D only
B. A and E only
C. B and D only
D. B and E only
evaporation. She got five identical towels and prepared five set-ups as shown
in the table below.
Variable
Set-up
A
B
C
D
E
Amount of water poured
onto the towel
30 ml
20 ml
30 ml
20 ml
30 ml
Number of times towel
was folded
2
3
2
2
3
Presence of a fan
Yes
Yes
No
Yes
No
Surrounding temperature
30 oC
30 oC
10 oC
30 oC
30 oC
Which two set-ups should she use to ensure that her experiment was fair?
A. A and D only
B. A and E only
C. B and D only
D. B and E only