Matter is typically characterized by:
Gas — no fixed volume or shape, and can be compressed or expanded as there is space between the molecules.
Liquid — distinct volume but no distinct shape, cannot be compressed.
Solid — definite volume and shape, cannot be compressed.
A pure substance (or substance) is matter that has distinct properties and a composition that does not vary sample to sample.
Two types of substances: elements and compounds.
Most elements can interact with other elements to form compounds. The elemental composition of a compound is always the same; this is called the law of constant composition.
In a mixture, each substance retains its chemical identity and properties. The composition of a mixture may vary in quantities.
Homogenous mixtures are also called solutions, even if they're not liquid.
All digits of a measured quantity, including the uncertain (last) digit, are called significant figures.
Determine significant figures by reading a number left to right and counting digits, starting with the first non-zero digit.
The zeroes in a number that ends with zeroes but contains no decimal point are assumed to be not significant.
However, this can be more clearly expressed with scientific notation: 1.03 * 10^4 (three significant digits) 1.0300 * 10^4 (five significant digits)
The result has the same number of decimal places as the measurement with the fewest decimal places.
Example: 20.42 + 83.1 = 103.52 ⇒ 103.5
83.1 only has one decimal place, so the answer must be rounded to one decimal place.
The result contains the same number of significant figures as the measurement with the fewest significant figures.
Example: 6.221 * 5.2 = 32.3492 ⇒ 32
5.2 only has two significant figures, so the answer must be rounded to two significant figures.
Dimensional analysis is the practice of multiplying or dividing units along with the numbers.
The key is using conversion factors, such as this one:
To calculate the units like this:
The inches cancel out on top and bottom leaving just centimeters.