STAT Scientific and Mathematical Reasoning 5 — Questions and Answers
Question 1: A solution turns red litmus paper blue. Which of the following is most consistent with this observation?
- The solution has a pH below 7
- The solution is acidic
- The solution contains excess OH⁻ ions (Correct answer)
- The solution is neutral
Correct answer: The solution contains excess OH⁻ ions
Red litmus turns blue in basic (alkaline) solutions, which have a pH above 7 and excess hydroxide ions.
Question 2: Three friends run a race. Their finishing times in seconds are 52, 58, 48, 61, and 46. What is the median finishing time?
- 52 (Correct answer)
- 53
- 58
- 48
Correct answer: 52
Ordered: 46, 48, 52, 58, 61; the middle value (3rd of 5) is 52 seconds.
Question 3: A chemical reaction produces a gas that extinguishes a burning splint. Which gas was most likely produced?
- Oxygen
- Hydrogen
- Carbon dioxide (Correct answer)
- Nitrogen monoxide
Correct answer: Carbon dioxide
Carbon dioxide does not support combustion and will extinguish a burning splint (oxygen relights a glowing splint; hydrogen burns with a squeaky pop).
Question 4: If the probability of event X occurring is 0.3 and the probability of event Y occurring is 0.5, and the two events are independent, what is the probability that neither X nor Y occurs?
- 0.15
- 0.20
- 0.35 (Correct answer)
- 0.65
Correct answer: 0.35
P(not X) = 0.7, P(not Y) = 0.5; P(neither) = 0.7 × 0.5 = 0.35.
Question 5: A student notices that ice melts faster in a black container than in a white container when both are placed in sunlight. The best scientific explanation is:
- Black containers conduct heat better than white ones
- Black surfaces absorb more radiant energy than white surfaces (Correct answer)
- White containers reflect cold air toward the ice
- The color of the container changes the melting point of ice
Correct answer: Black surfaces absorb more radiant energy than white surfaces
Dark surfaces absorb more electromagnetic radiation and convert it to heat, accelerating the melting of the ice.
Question 6: A square has its side length doubled. By what factor does its area increase?
- 2
- 3
- 4 (Correct answer)
- 8
Correct answer: 4
Area = s²; doubling s gives (2s)² = 4s², so the area increases by a factor of 4.
Question 7: In a food web, removing the top predator typically leads to:
- Immediate extinction of all prey species
- Population increase of prey and potential collapse of vegetation (Correct answer)
- Decrease in the prey population due to reduced competition
- No change because energy flow is unaffected
Correct answer: Population increase of prey and potential collapse of vegetation
Without top predators, prey populations grow unchecked (trophic cascade), which can overgraze vegetation and destabilize the ecosystem.
STAT Scientific and Mathematical Reasoning 5
A solution turns red litmus paper blue.
Which of the following is most consistent with this observation?