Question

module 0: intro. to chemistry and measurement
module 0 study guide
(to receive full credit, show all calculations when needed.)

1. the average distance between the earth and the moon is 386,000 km. express this in scientific notation.
2. how would 0.00930 m be expressed in scientific notation?
3. a student carried out an experiment 3 different times. the accepted value for the results is 1.43.

describe this student’s experimental data in terms of accuracy and precision. (good or poor)

trial	measurement
2	1.93
3	0.88

accuracy? precision?

1. a student carried out an experiment 3 different times. the accepted value for the results is 15.63.

describe this student’s experimental data in terms of accuracy and precision. (good or poor)

trial	measurement
2	11.02
3	10.96

accuracy? precision?

1. an experimental value of 13.1 is calculated. the accepted value is 12.8. what is the percent error?
2. during an investigation, a student determines that a copper sample has a density of 8.10 g/ml. what is the student’s percent error if the accepted density for copper is 8.96 g/ml?
3. what are the correct measurements to the correct number of significant digits? incluce units!

a. image of a ruler with a red block
b. image of a graduated cylinder with green liquid
c. image of a graduated cylinder with yellow liquid

Explanation:

Step1: Convert to scientific notation

$386,000 = 3.86 \times 10^5$ km

Step2: Convert to scientific notation

$0.00930 = 9.30 \times 10^{-3}$ m

Step3: Evaluate accuracy and precision

Accuracy: Poor (values far from 1.43)
Precision: Poor (values spread widely)

Step4: Evaluate accuracy and precision

Accuracy: Poor (values far from 15.63)
Precision: Good (values close to each other)

Step5: Calculate percent error

$\text{Percent Error} = \frac{|13.1 - 12.8|}{12.8} \times 100\% = \frac{0.3}{12.8} \times 100\% \approx 2.34\%$

Step6: Calculate percent error

$\text{Percent Error} = \frac{|8.10 - 8.96|}{8.96} \times 100\% = \frac{0.86}{8.96} \times 100\% \approx 9.60\%$

Step7: Read measurements with sig figs

a. Ruler reads 1.90 cm (est. to 0.01 cm)
b. Graduated cylinder reads 22.5 L (est. to 0.1 L)
c. Graduated cylinder reads 1.40 mL (est. to 0.01 mL)

Answer:

1. $\boldsymbol{3.86 \times 10^5}$ km
2. $\boldsymbol{9.30 \times 10^{-3}}$ m
3. Accuracy: Poor; Precision: Poor
4. Accuracy: Poor; Precision: Good
5. $\boldsymbol{\approx 2.34\%}$
6. $\boldsymbol{\approx 9.60\%}$
7. a. $\boldsymbol{1.90\ \text{cm}}$; b. $\boldsymbol{22.5\ \text{L}}$; c. $\boldsymbol{1.40\ \text{mL}}$