Question

a group of students wanted to investigate what happens to a solution as more solute is added. they filled two beakers, each with 500 ml of water. they began adding the solute, table salt (nacl) to the water in increments of 5 grams to the first beaker. each time they added salt, they stirred the solution for 1 minute, then allowed the solution to settle out. they observed the solution and recorded whether they could observe any salt crystals at the bottom of the beaker. they did not add any salt to the second beaker, but they stirred it each time they stirred the water in the first beaker. they observed the water and recorded their observations. their results are shown in the table below.
this is an example of which type of scientific investigation?
a) comparative
b) controlled
c) descriptive
d) experimental

Explanation:

In this investigation, the students have two beakers. Beaker 1 has salt added (the independent variable), and they observe the solution (the dependent variable). Beaker 2 acts as a control (no salt added). A controlled experiment has an experimental group (Beaker 1) and a control group (Beaker 2) to compare results. A comparative study would compare two different natural phenomena without manipulation. A descriptive study just describes a single phenomenon without comparison or manipulation. An explorative study is more about exploring a new area without a clear hypothesis - testing setup like this one. Here, the setup with control and experimental group to test the effect of salt addition (manipulation) makes it a controlled experiment.

Answer:

B. controlled