Chapter 1 Notes: Particles of Matter and Measurement Tools

Atom

The smallest particle of an element that retains the chemical characteristics of that element.

Molecule

An assembly of two or more atoms that are held together in a characteristic pattern by chemical bonds.

Ions

Positively or negatively charged particles found in some compounds.

Cations

Positively charged ions, e.g., ext{Ca}^{2+}, ext{Na}^{+}.

Anions

Negatively charged ions, e.g., ext{Cl}^{-}, ext{OH}^{-}.

Rounding Procedure (>= 5 rule)

If the leftmost digit to be dropped is 5 or greater, add 1 to the last digit to be retained; drop all digits farther to the right.

Rounding Procedure (< 5 rule)

If the leftmost digit to be dropped is less than 5, drop all digits farther to the right.

Exponential Notation (Scientific Notation)

A method to express very large or very small numbers, in the form N \times 10^n where N is between 1 and 9 and n is an integer.

Nonzero Integers (Significant Figures)

All nonzero integers are always significant.

Leading Zeros (Significant Figures)

Leading zeros (zeros before nonzero digits) are not significant, e.g., 0.0392 has 3 sig figs.

Trailing Zeros (Significant Figures)

Trailing zeros are not significant unless they come after a decimal point, e.g., 3700 has 2 sig figs, 140.00 has 5 sig figs.

Captive Zeros (Significant Figures)

Zeros between nonzero digits are always significant, e.g., 16.07 has 4 sig figs.

Significant Figures in Multiplication/Division

The result should have the same number of significant figures as the measurement with the fewest significant figures used in the calculation.

Significant Figures in Addition/Subtraction

The result should have the same number of decimal places as the measurement with the fewest decimal places used in the calculation.

Kelvin to Celsius Conversion

K = °C + 273.15

Celsius to Fahrenheit Conversion

°F = \tfrac{9}{5}°C + 32

Fahrenheit to Celsius Conversion

°C = \tfrac{5}{9}(°F - 32)

Unit Conversion Factor

A ratio derived from an equality (e.g., 1\text{ km} = 0.6214\text{ mi}) used to convert a value from one unit to another, typically in the form (Desired units / Initial units).

Density (d)

The ratio of mass to volume, expressed as d = \frac{m}{V}.

Common Density Units (Solids)

\text{g/cm}^3

Common Density Units (Liquids)

\text{g/mL}

Common Density Units (Gases)

\text{g/L}

Derived Units

Combinations of fundamental units, such as m^2 for area, m^3 for volume, or m/s for speed.

Quantity

A property that can be measured, such as length, mass, or time.

SI Unit for Length/Distance

\text{m} (meter)

SI Unit for Mass

\text{kg} (kilogram)

SI Unit for Time

\text{s} (second)