Paul's class investigated the effects of friction on the motion of a toy car. Using
ramps with different surfaces, students determined the amount of time, in seconds
(s), for the toy cars to reach the bottom of each ramp. All variables were controlled
except the tested variable (independent variable). Paul's group concluded that toy
cars on a sandpaper surface are fastest.
Which statement best evaluates the groups conclusion?
A. The results support the conclusion
B. More data need to be added to the conclusion
C. The conclusion is valid for the data recorded
D. The results fail to support the conclusion

One way in which the useful metal copper is produced is by dissolving the mineral azurite, which contains copper(ii) carbonate, in concentrated sulfuric acid. the sulfuric acid reacts with the copper(ii) carbonate to produce a blue solution of copper(ii) sulfate. scrap iron is then added to this solution, and pure copper metal precipitates out because of the following chemical reaction: (s) (aq) (s) (aq) suppose an industrial quality-control chemist analyzes a sample from a copper processing plant in the following way. he adds powdered iron to a copper(ii) sulfate sample from the plant until no more copper will precipitate. he then washes, dries, and weighs the precipitate, and finds that it has a mass of .