3.1. Units of Measurement http://www.ck12.org
- 655 × 102 mL^2
Lesson Summary
- Measurement is the process of making an observation in terms of a numerical scale and recording the value.
- In chemistry, we measure things that range from extremely small to extremely large. Common quantities
measured include distance, mass, time, temperature, volume, density, pressure, amount, concentration, energy,
velocity, molarity, viscosity, and electric charge. - Because chemistry deals with very large and very small physical quantities, we utilize powers of 10 to express
base units and derived units. - Base units have independent scales and cannot be described by a combination of any other base units. Exam-
ples of base units used in chemistry are length, mass, temperature, and time. - Derived units can be expressed as some combination of base units. Examples of derived units are area, volume,
and speed. - The Systeme International (SI) is a standard metric system of units that is used by scientists.
- Dimensional analysis is a method of problem solving in which conversion factors are arranged so that a value
can be converted from one set of units to another.
Lesson Review Questions
- Convert the following numbers to scientific notation.
a. 13,000,000
b. 4020.0
c. 0.00040
d. 0.0004002 - Convert the following using conversion factors given in the table of Commonly Used SI Prefixes.
a. 126 kg to grams
b. 826 mL to L
c. 2.45× 10 −^12 g to nanograms
d. 1.24× 10 −^12 meters to picometers - Perform the following calculations, and write your final answer in scientific notation.
a. 1.06× 103 kilograms + 8.6× 1013 nanograms
b. 100.06 mL + 35 L
c. 3.56× 105 cm + 1.23× 102 m - Which SI unit and prefixes would be used to report the following
a. A person’s weight
b. The length of a ladybug
c. The volume of a large lake
d. The weight of a human hair
e. The width of a human hair - Calculate the number of seconds in the month of December.
- How many donuts can you buy with $23.00 if they cost $3.00/dozen?
- A light year is the distance light travels in one year. Sirius (the dog star), the brightest in the sky, is
approximately 8.6 light years from earth. How far (in km) from earth is it if light travels 3.0× 108 m/s?