PISA - Program for International Student Assessment Scientific Literacy and Enquiry Questions and Answers — Questions and Answers
Question 1: A student conducts an experiment to test the hypothesis that caffeine increases the heart rate of daphnia (water fleas). She places a daphnia on a microscope slide in a drop of water and measures its heart rate. She then adds a drop of caffeine solution and measures the heart rate again. To ensure the reliability of her results, which of the following is the most important next step?
- Testing a different type of organism to see if it reacts the same way.
- Using a stronger concentration of caffeine to get a more obvious result.
- Repeating the experiment multiple times with different daphnia. (Correct answer)
- Publishing her single result immediately to claim the discovery.
Correct answer: Repeating the experiment multiple times with different daphnia.
In scientific enquiry, repeatability is crucial for establishing reliability. A single result could be an anomaly. By repeating the experiment with multiple subjects under the same conditions, the student can determine if the observed effect is consistent and not due to chance or individual variation in the daphnia.
Question 2: On a humid day, small droplets of water form on the outside of a glass of ice-cold water. Which of the following statements best explains this phenomenon scientifically?
- The cold temperature causes the glass to sweat out water from within its structure.
- The ice inside the glass is melting and seeping through microscopic pores.
- Water vapor from the surrounding air cools and condenses into liquid on the cold surface. (Correct answer)
- Oxygen and hydrogen atoms from the air spontaneously combine to form water on the glass.
Correct answer: Water vapor from the surrounding air cools and condenses into liquid on the cold surface.
This is an example of condensation. The air contains invisible water vapor. When the warm, moist air comes into contact with the cold surface of the glass, it cools down. This causes the water vapor to change its state from a gas to a liquid, forming droplets.
Question 3: A team of researchers wants to investigate the effects of a new running shoe on athletic performance. Which of the following questions is a scientific question that can be investigated through their experiment?
- Do the new running shoes look better than the old ones?
- Is the price of the new running shoes fair for the technology they use?
- Does wearing the new shoes make runners feel happier?
- Does running in the new shoes affect a runner's 100-meter sprint time? (Correct answer)
Correct answer: Does running in the new shoes affect a runner's 100-meter sprint time?
A scientific question must be testable and allow for the collection of measurable data. Sprint time is a quantifiable variable that can be measured and compared between runners wearing the new shoes and those wearing other shoes. The other options are based on subjective opinion (looks, happiness) or economic judgment (fair price), not direct scientific measurement.
Question 4: A student reads a blog post that claims, 'Using a smartphone for more than two hours a day is guaranteed to cause brain damage.' As a scientifically literate citizen, what should be the student's most critical first step?
- Immediately stop using their smartphone for more than two hours.
- Accept the claim as true because it sounds serious and scientific.
- Share the blog post with friends to warn them of the danger.
- Look for the evidence and the source of the claim to evaluate its credibility. (Correct answer)
Correct answer: Look for the evidence and the source of the claim to evaluate its credibility.
A core competency of scientific literacy is to evaluate scientific information and its sources. Extraordinary claims require strong evidence. Before accepting or acting on such a claim, a scientifically literate person would question the source, look for supporting data from reputable studies, and consider whether the claim is based on scientific research or opinion.
Question 5: In a well-designed scientific experiment, what is the purpose of a 'control group'?
- To have a group that can be stopped if the experiment goes wrong.
- To provide a baseline for comparison with the experimental group. (Correct answer)
- To test multiple variables at the same time on one group.
- To ensure the researchers have control over the weather.
Correct answer: To provide a baseline for comparison with the experimental group.
The control group is a group in an experiment that does not receive the experimental treatment. By comparing the results of the experimental group (which receives the treatment) to the control group, scientists can determine if the variable they are testing has a significant effect. It serves as a baseline to measure the change against.
Question 6: A graph in a health report shows that as ice cream sales increase, the number of drowning incidents also increases. The report concludes that eating ice cream causes drowning. Why is this conclusion likely flawed?
- The graph is probably inaccurate because ice cream is a solid and can't cause drowning.
- The conclusion ignores a likely third variable, such as warm weather, that causes both to increase. (Correct answer)
- The conclusion is valid because the data shows a clear positive correlation.
- The study should have been conducted in winter to get more accurate results.
Correct answer: The conclusion ignores a likely third variable, such as warm weather, that causes both to increase.
This is a classic example of confusing correlation with causation. While the two variables increase together (correlation), one does not necessarily cause the other. A third, unmentioned variable—warm weather—is the likely cause of both increases. In warm weather, more people buy ice cream, and more people go swimming, which leads to a higher number of drowning incidents.
PISA - Program for International Student Assessment Scientific Literacy and Enquiry Questions and Answers
A student conducts an experiment to test the hypothesis that caffeine increases the heart rate of daphnia (water fleas).
She places a daphnia on a microscope slide in a drop of water and measures its heart rate.
She then adds a drop of caffeine solution and measures the heart rate again.
To ensure the reliability of her results, which of the following is the most important next step?