Question

use diagrams a - c to answer questions # 23 & 24

1. record the volume of water in each of the following beakers to the correct number of sig figs.
2. using you recorded measurements from #20, calculate the total volume of water with correct sig figs and units. (sum of all beakers)
3. a student was asked to find the density of an unknow object. the student found that the mass of the object was 35.49 g. the student used water displacement to find the volume of the object. the graduated cylinder originally contained 45.1 ml of water. after the object was placed in the graduated cylinder, the volume was 52.3 ml. what is the density of the unknown object? prove all of your work below. remember to watch sig figs and units. show formulas used.

volume =
d = \frac{m}{v}
d = \frac{g}{cm^{3}}
d = g/cm^{3}

Explanation:

Step1: Read volumes for question 23

A: 26.0 mL (the meniscus is at 26 and we estimate one more digit. Since the scale is in 1 - unit intervals, we write 26.0 to show precision). B: 30.0 mL (the meniscus is at 30 and we estimate one more digit). C: 26.4 mL (read the value where the meniscus is located).

Step2: Calculate total volume for question 24

$V_{total}=26.0\ mL + 30.0\ mL+26.4\ mL=82.4\ mL$

Step3: Calculate volume of object for question 25

$V = V_{final}-V_{initial}=52.3\ mL - 45.1\ mL = 7.2\ mL$ (1 mL = 1 $cm^{3}$, so $V = 7.2\ cm^{3}$)

Step4: Calculate density of object for question 25

Using the formula $D=\frac{m}{V}$, with $m = 35.49\ g$ and $V = 7.2\ cm^{3}$, we have $D=\frac{35.49\ g}{7.2\ cm^{3}}\approx4.9\ g/cm^{3}$ (rounded to 2 sig - figs as 7.2 has 2 sig - figs).

Answer:

1. A: 26.0 mL, B: 30.0 mL, C: 26.4 mL
2. 82.4 mL
3. Volume = 7.2 $cm^{3}$, $D\approx4.9\ g/cm^{3}$