Question

Two groups of students competed to see who could dissolve 5 grams of salt in 50 mL of water the fastest. The table shows the methods they used.

Step Group X Group Y
1 measured 50 mL of water into a 200 mL graduated cylinder measured 50 mL of water into a 100 mL graduated cylinder
2 added 5 grams of salt with a cup added 5 grams of salt with a spoon
3 stirred gently for 1 minute stirred vigorously for 1 minute
4 recorded the time with a stopwatch recorded the time with a wristwatch

Which group most likely dissolved the salt faster?
A.

group X because they used a larger cylinder

B.

group X because they used a cup to add the salt

C.

group Y because they stirred the water vigorously

D
.

group Y because they used a wristwatch to record time

Answer 1

C. group Y because they stirred the water vigorously

Vigorous stirring increases the rate of dissolution by bringing fresh solvent into contact with the salt and reducing the concentration boundary layer, so the salt dissolves faster. The cylinder size, scooping tool, or type of watch don't speed up dissolution.