Question

pre - lab study questions | 3

1. what property of oil makes it float on water?
2. why would heating the gas in a hot air balloon make the balloon rise?
3. what is the difference between density and specific gravity?
4. an object has a mass of 18.4 g and a volume of 11.2 ml.

a. what is the density of the object?
b. what is the specific gravity of the object?
c. will the object sink or float in water?

1. a 15.0 g - sample of a liquid has a density of 0.875 g/ml.

a. what is the volume, in milliliters, of the liquid? use conversion factors to calculate answer.
b. what mass, in grams, of the liquid is in 34.6 ml of the liquid?

Explanation:

Step1: Recall density formula

Density ($
ho$) is given by $
ho=\frac{m}{V}$, where $m$ is mass and $V$ is volume.

Step2: Calculate density for object in question 4a

Given $m = 18.4$ g and $V=11.2$ mL, $
ho=\frac{18.4}{11.2}\approx1.64$ g/mL.

Step3: Recall specific - gravity formula

Specific gravity (SG) is the ratio of the density of a substance to the density of a reference substance (usually water at 4°C with density $
ho_{water}=1$ g/mL). So for the object in 4b, $SG = \frac{
ho_{object}}{
ho_{water}}$. Since $
ho_{object}\approx1.64$ g/mL, $SG\approx1.64$.

Step4: Determine buoyancy for 4c

If the density of the object is greater than the density of water (1 g/mL), it will sink. Since $
ho_{object}\approx1.64$ g/mL > 1 g/mL, the object will sink.

Step5: Calculate volume for 5a

Given $m = 15.0$ g and $
ho=0.875$ g/mL, using $V=\frac{m}{
ho}$, we have $V=\frac{15.0}{0.875}\approx17.1$ mL.

Step6: Calculate mass for 5b

Given $V = 34.6$ mL and $
ho=0.875$ g/mL, using $m=
ho V$, we get $m = 0.875\times34.6\approx30.3$ g.

Answer:

4a. The density of the object is approximately 1.64 g/mL.
4b. The specific gravity of the object is approximately 1.64.
4c. The object will sink.
5a. The volume of the liquid is approximately 17.1 mL.
5b. The mass of the liquid is approximately 30.3 g.