Q: A sample of zinc metal is submerged in a graduated cylinder containing water. The water level rises from 21.0 mL to 24.5 mL. If the density of zinc is $$7.14\ \mathrm{g/mL}$$, what is the mass of the zinc sample?

$$m = (24.5 - 21.0)\ \mathrm{mL} \times 7.14\ \mathrm{g/mL} = 24.99\ \mathrm{g}$$

Q: A student needs to convert 68.0 inches to centimeters. Given that $$1\ \mathrm{in} = 2.54\ \mathrm{cm} ($$exact), what is the correct answer with the proper number of significant figures?

$$68.0\ \mathrm{in} \times 2.54\ \mathrm{cm/in} = 172.7\ \mathrm{cm}$$

Question 1

Which of the following best describes a scientific law?

Accepted Answer

A statement, often mathematical, that summarizes the results of many experiments and describes what happens, but does not explain why.

Question 2

A sample of a metal has a mass of 45.0 g and a volume of 15.0 mL. What is its density, and is density an intensive or extensive property?

Accepted Answer

$$d = \frac{45.0\ \mathrm{g}}{15.0\ \mathrm{mL}} = 3.00\ \mathrm{g/mL}$$; density is an intensive property.

Question 3

Which of the following is a chemical change?

Accepted Answer

Iron rusting when exposed to air.

Question 4

A student measures the mass of a beaker as 65.230 g using a digital balance. What is the uncertainty in this measurement, and how should it be reported?

Accepted Answer

The uncertainty is $$\pm 0.005\ \mathrm{g}$$; report as $$65.230 \pm 0.005\ \mathrm{g}.$$

Question 5

Which of the following is a homogeneous mixture?

Accepted Answer

Air in a room.

Question 6

Convert 25.0 °C to Kelvin.

Accepted Answer

$$T_K = 25.0 + 273.15 = 298.15\ \mathrm{K}$$

Question 7

A sample of zinc metal is submerged in a graduated cylinder containing water. The water level rises from 21.0 mL to 24.5 mL. If the density of zinc is $$7.14\ \mathrm{g/mL}$$, what is the mass of the zinc sample?

Accepted Answer

$$m = (24.5 - 21.0)\ \mathrm{mL} 	imes 7.14\ \mathrm{g/mL} = 24.99\ \mathrm{g}$$

Question 8

Which of the following numbers has four significant figures?

Accepted Answer

0.04560

Question 9

A student needs to convert 68.0 inches to centimeters. Given that $$1\ \mathrm{in} = 2.54\ \mathrm{cm} ($$exact), what is the correct answer with the proper number of significant figures?

Accepted Answer

$$68.0\ \mathrm{in} 	imes 2.54\ \mathrm{cm/in} = 172.7\ \mathrm{cm}$$

Question 10

Which of the following is an example of an extensive property?

Accepted Answer

Mass

Question 11

A titanium hip joint has a mass of 205 g and a density of $$4.51\ \mathrm{g/cm^3$}. $$What volume does it occupy?

Accepted Answer

$$V = \frac{205\ \mathrm{g}}{4.51\ \mathrm{g/cm^3$}} = 45.5\ \mathrm{cm^3$}$$

Question 12

Which of the following best describes the difference between accuracy and precision?

Accepted Answer

Accuracy is how close measurements are to the true value; precision is how close repeated measurements are to each other.

Question 13

A solution is prepared by dissolving 5.00 g of NaCl in 100.0 g of water. Which statement is correct about the resulting mixture?

Accepted Answer

It is a homogeneous mixture because the salt is evenly distributed throughout the water.

Question 14

Round the number 0.00564458 to four significant figures and express it in scientific notation.

Accepted Answer

$$5.645 	imes 10$$^{-3}$$

Question 15

A laboratory thermometer reads 121 °F. What is this temperature in Kelvin?

Accepted Answer

$$T_C = \frac{121 - 32}{1.8} = 49.4\ ^\circ\mathrm{C}$$;\ T_K = 49.4 + 273.15 = 322.6\ \mathrm{K}$

Question 16

A car has a gas mileage rating of 56 miles per gallon. What is this rating in kilometers per liter? ($$1\ \mathrm{mile} = 1.609\ \mathrm{km}$$, $$1\ \mathrm{gal} = 3.784\ \mathrm{L})$$

Accepted Answer

$$\frac{56\ \mathrm{mi}}{1\ \mathrm{gal}} 	imes \frac{1.609\ \mathrm{km}}{1\ \mathrm{mi}} 	imes \frac{1\ \mathrm{gal}}{3.784\ \mathrm{L}} = 23.8\ \mathrm{km/L}$$

Question 17

Which of the following best describes an exact number in chemistry?

Accepted Answer

A number that has no uncertainty and is obtained by definition or counting.

Question 18

A sample of glass has a density of $$2.50\ \mathrm{g/cm^3$}. $$What is the mass of $$15.0\ \mathrm{cm^3$} of $$glass?

Accepted Answer

$$m = 15.0\ \mathrm{cm^3$} 	imes 2.50\ \mathrm{g/cm^3$} = 37.5\ \mathrm{g}$$

Question 19

When adding $$412.272 + 0.00031 - 1.00797 + 0.000024 + 12.8$$, to which decimal place should the answer be reported?

Accepted Answer

Tenths place

Chapter 1: Scientific Measurements and Classification of Matter

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