Entry Exam Category: High School Equivalency Exams
Course: General Education Development (GED)
Exam: GED Science and Practice Test
Practice Question
Extract
Salt water causes marine ecosystems to be very different from freshwater ecosystems. Organisms in both types of ecosystems are affected by the freezing and melting of ice. An experiment was conducted to test the hypothesis that ice melts faster in salt water than in fresh water. Ice cubes made of fresh water were placed into cups containing either fresh water or salt water. Various data were recorded, and the energy released by each melting ice cube was calculated from the data. The table shows the results for each cup.
What statement describes one or more needed changes to this experiment that would allow the experimenter to draw a valid conclusion?
Answer Choices
- A: Salt water should have been used to make the ice cubes for the cup of salt water.
- B: The time for ice cubes to melt should have been measured in minutes.
- C: At the beginning, both cups should have contained the same mass of water at the same temperature.
- D: The energy released should have been measured, not calculated.
Correct Answer: C
Rationale: Standardizing initial conditions (mass and temperature of water) ensures a controlled experiment.