Question

1. What is the effect on the calculated density of the unknown metal or liquid under the following conditions?

1. After the flask was filled with unknown liquid the cover slip was placed on top. In doing so a small air bubble was trapped under the cover slip.

2. When determining the density of the unknown metal, the flask was filled less than one quarter way with the metal instead of halfway.

3. When determining the volume of the flask, the student did not fill the flask completely with water and left approximately 1 ml or air at the top of the flask prior to weighting it. What will be the effect on the measured density of the unknown liquid and the unknown solid?

4. The student didn’t get all of the trapped air out of the flask when it contained the metal and was filled to the top with water.

5. When determining the density of the metal unknown, the flask was filled less than halfway with metal instead of 2/3 of the way as instructed.

Answer 1

a. The trapped air bubble will increase the volume of the liquid while the mass remains constant. Since the density of the liquid is the quotient of the mass and the volume, hence, an increased volume will reduce the density of the liquid.

b. The flask was filled less than that required by the procedure. The volume of the metal is equal to the volume of the displaced liquid. Since the volume of the metal remains unchanged, hence, the volume of the liquid will remain unchanged and thus, the density will remain constant.

c. The volume of the flask is assumed equal to the volume of the liquid. Since the liquid didn’t fill the flask completely, hence, the volume of the liquid and thus, that of the flask will be computed lower than the actual value. The apparent density of the metal is equal to the mass divided by the volume. Thus, a lower mass will register a higher density.

d. The trapped air will increase the volume of the flask and thus, the calculated density of the metal will be low.

e. The mass of the metal was taken lower than instructed. However, the volume of the liquid was kept constant. Thus, a lower mass will register a lower density for the metal.