Question

five groups of students in mr. walkers science class performed an experiment to determine the effect of salt on the boiling point of water. each group dissolved 5g of salt in 100ml of distilled water, heated the solution and recorded the boiling point with a thermometer that had divisions of 0.1°c. each group obtained exactly same boiling point for the salt solution, 100.8°c. are the results valid? a no, because too little salt was used. b no, because it was not a controlled experiment. c yes, because each group obtained the same results. d yes, because the thermometer had divisions of 0.1°c.

Explanation:

For an experiment to be valid, it should be a controlled experiment. Here, there is no mention of a control group (pure water without salt for comparison). Just because groups got the same result or the thermometer has a certain precision or the amount of salt used doesn't guarantee validity.

Answer:

B. No, because it was not a controlled experiment.