A text states that a pendulum's period depends only on its length. Students time 50-cm pendulums carrying 50-g, 100-g and 200-g bobs and record 1.4 seconds for every bob. What does the comparison show?

An article says pure water freezes at 0 degrees Celsius. A group freezes salt water and records a freezing point of about -3 degrees Celsius in all four trials. What best explains the difference?

A textbook states that a moving object keeps moving unless an unbalanced force acts on it. A rolling cart released on classroom carpet slows and stops after four meters. Which statement fairly compares the two?

A book says that, apart from air resistance, all objects fall with the same acceleration. A video shows a feather and a steel ball dropped in a vacuum tube landing together, then landing far apart in ordinary air. What does the video add?

A text says chlorophyll absorbs red and blue light strongly and reflects most green light. Seedlings gain 6 cm under red light, 5 cm under blue and 2 cm under green over two weeks. How do the sources relate?

An article states that more sugar can dissolve in hot water than in cold. Timing trials show one sugar cube vanishing in 30 seconds at 60 degrees Celsius and in 150 seconds at 10 degrees Celsius. What does the experiment add?

A text says a magnet's pull weakens as distance grows. Students find a magnet lifting 12 paper clips at 1 cm, 5 clips at 3 cm and 1 clip at 5 cm. Which statement best compares the sources?

A textbook states that dark surfaces absorb more radiant energy than light ones. Under one lamp, water in a black can warms 8 degrees Celsius while water in a white can warms 3 degrees Celsius in 20 minutes. What does the comparison show?

An article says water evaporates faster from a wide container than a narrow one. Equal 100-mL samples left three days lose 40 mL from a wide dish and 12 mL from a jar. How do the sources compare?

A text says mass is conserved in a chemical reaction. Vinegar and baking soda in an open cup drop from 82 g to 79 g, while the same amounts sealed in a bag stay at 82 g. What explains the open cup?

A text says predator numbers rise after prey numbers rise. A simulation graphs rabbit peaks in years 3 and 9 and fox peaks in years 4 and 10. What does the simulation contribute?

A text says an object sinks when it is denser than water. A solid clay ball sinks, yet the same lump of clay shaped into a bowl floats. Which statement best resolves the two results?

A textbook states that adding bulbs in series lowers the current in a circuit. Students measure 0.30 A with one bulb, 0.16 A with two bulbs and 0.11 A with three. What does the comparison show?

An article says sound travels faster through solids than through air. Standing 30 m away, students hear a hammer tap arrive through a metal rail before they hear the same tap through the air. What do the sources show together?

A text says a crushed tablet reacts faster than a whole one because more surface meets the liquid. Trials show a whole tablet fizzing for 95 seconds and a crushed tablet for 28 seconds. What do the trials add?

A textbook states that metals conduct heat better than wood. With both handles out of hot water, a metal spoon handle reads 48 degrees Celsius after two minutes and a wooden spoon handle reads 26 degrees Celsius. Which comparison holds?

A text says green plants need light to make food. Bean seeds sprouted inside a dark box grow 8-cm shoots in five days, then turn pale and die by day twelve. What does the experiment show that the text does not?

A class tests its model bridge two hours after gluing, though the label says the glue takes a day to harden. It fails at 18 kg, while a text predicts 25 kg for that design. Which response to the gap is a reasoned judgment rather than speculation?

A text says warm air can hold more water vapor than cold air. A class weighs a sealed jar of warm moist air, chills it, and finds no change in mass although drops appear inside. Which comparison is accurate?

A text says ice melts at 0 degrees Celsius. A time-lapse video shows a cup of ice water holding at 0 degrees Celsius for eight minutes as the ice disappears, then climbing steadily. What does the video reveal?