Question

A student measures 10.5 ml of blue liquid in a graduated cylinder and 5.2 ml of red liquid in another graduated cylinder. She then pours the red liquid into the graduated cylinder containing the blue liquid, and the liquids do not mix. Instead, the red liquid remains on top of the blue liquid.

A) What causes the red liquid to remain on top of the blue liquid?

B) Have you seen two liquids that do not mix before? What were they?

C) What is the volume of the two liquids after they were combined?

D) Would you be able to easily separate the liquids in this case? How would you do that?

Answer 1

A) The red liquid has less density than blue liquid, so it remains on top of the blue liquid.

B) Yes. They are water and oil. They do not mix. Oil floats on top of the water, because its density is lower than water.

C)

Student pours the red liquid into the graduated cylinder containing the blue liquid, and the liquids do not mix, so there is do no decrease in volume of solution.

Volume of the two liquids after they were combined = 10.5 ml + 5.2 ml = 15.7 ml.

D)

Yes, we would be able to easily separate the liquids in this case by using a separating funnel. The two liquids are put into the funnel and are left for a short time to settle out and form two layers. Red liquid settle on top and blue liquid on bottom. The tap of the funnel is opened and the bottom liquid is allowed to run. The two liquids are now separated.