Chem 103 Chp 2: Unit Measurements

Scientific Notation

A way to write very large or very small numbers using powers of 10.

Standard Notation

The usual way to write numbers, not in scientific notation.

Accuracy

How close a measurement is to the true value.

Do they relect True value

Precision

How close repeated measurements are to each other.

Significant Digits

Digits in a measurement that carry meaning contributing to its precision.

Exact Numbers

Values that are known with complete certainty.

Dimensional Analysis

A method of converting units by multiplying by conversion factors.

Boiling Point of Water

The temperature at which water changes from a liquid to a gas.

Freezing Point of Water

The temperature at which water changes from a liquid to a solid.

Absolute Zero

The lowest possible temperature where nothing could be colder and no heat energy remains in a substance.

Celsius to Fahrenheit

F = (9/5)C + 32

Fahrenheit to Celsius

°C = 5/9(°F −32)

Celsius to Kelvin

K = °C + 273.15

4 Rules of Sif Figs

1. All nonzero digits are significant, and all zeros between nonzero digits are significant

2. If a decimal point is present, zeros to the right of the last nonzero digit are significant.

3. Zeros to the left of the nonzero numbers are never significant.

4. If there is no decimal point present, zeros to the right of the last nonzero may or may not be significant.

Multiply and Divide Sig Figs

When multiplying or dividing, report the same number of digits as are in the least precise starting measurement.

Add and Subtract Sig Figs

When adding or subtracting, round to the last decimal place of the least precise starting measurement.

Density

Mass/Volume