Problem 23
A measurement is a quantitative observation involving both a number and a unit. What is a qualitative observation? What are the SI units for mass, length, and volume? What is the assumed uncertainty in a number (unless stated otherwise)? The uncertainty of a measurement depends on the precision of the measuring device. Explain.
Problem 24
To determine the volume of a cube, a student measured one of the dimensions of the cube several times. If the true dimension of the cube is 10.62 cm, give an example of four sets of measurements that would illustrate the following. a. imprecise and inaccurate data b. precise but inaccurate data c. precise and accurate data Give a possible explanation as to why data can be imprecise or inaccurate. What is wrong with saying a set of measurements is imprecise but accurate?
Problem 26
A cold front moves through and the temperature drops by 20 degrees. In which temperature scale would this 20 degree change represent the largest change in temperature?
Problem 27
When the temperature in degrees Fahrenheit \(\left(T_{\mathrm{F}}\right)\) is plotted vs. the temperature in degrees Celsius \(\left(T_{\mathrm{C}}\right),\) a straight-line plot results. A straight-line plot also results when \(T_{\mathrm{C}}\) is plotted vs. \(T_{\mathrm{K}}(\text { the temperature in kelvins). Reference Appendix } \mathrm{A} 1.3 \text { and }\) determine the slope and \(y\) -intercept of each of these two plots.
Problem 28
In a multiple-step calculation, is it better to round off the numbers to the correct number of significant figures in each step of the calculation or to round off only the final answer?
Problem 29
Is the density of a gaseous substance larger or smaller than the density of a liquid or a solid at the same temperature? Why?
Problem 30
Give four examples illustrating each of the following terms. a. homogeneous mixture b. heterogeneous mixture c. compound d. element e. physical change f. chemical change
Problem 31
Which of the following are exact numbers? a. There are 100 cm in 1 m. b. One meter equals 1.094 yards. c. We can use the equation $$^\circ \mathrm{F}=\frac{9}{5}^{\circ} \mathrm{C}+32$$ to convert from Celsius to Fahrenheit temperature. Are the numbers \(\frac{9}{5}\) and 32 exact or inexact? d. \(\pi=3.1415927\)
Problem 33
How many significant figures are there in each of the following values? a. \(6.07 \times 10^{-15}\) b. 0.003840 c. 17.00 d. \(8 \times 10^{8}\) e. 463.8052 f. 300 g. 301 h. 300
Problem 34
How many significant figures are in each of the following? a. 100 b. \(1.0 \times 10^{2}\) c. \(1.00 \times 10^{3}\) d. 100 e. 0.0048 f. 0.00480 g. \(4.80 \times 10^{-3}\) h. \(4.800 \times 10^{-3}\)
