Question

Five groups of students in Mr. Walker's 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?

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.

Answer 1

The correct answer is C. 
From the information given above, we are told that each of the five group carry out exactly the same experiment and they obtain exactly the same result. This shows that the experiment is valid. An experiment is said to be valid if different researchers carry out the same experiment and obtain similar results.

Answer 2

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

A controlled experiment isolates the effect of one variable. The groups must also measure the boiling point of the distilled water.