Unit 3

Scientific Measurement

Types of Measurement

• Qualitative– Gives results in nonnumeric, descriptive form.• Example: looking at a picture and evaluating if it’s a

good picture or not.

• Quantitative– Gives results in a definite form, usually in

numbers.• Example: looking at a picture and recording the exact

number of people, number of different kinds of animals, etc.

Accuracy - v - Precision

• Accuracy = “closeness” to the standard or exact value.• Precision = “closeness” to the standard or exact value

of several measurements.*accuracy is the value of the measurement in terms of good

or bad whereas precision is how consistent (reproducible) the measurement is.

example: kicking field goalsaccuracy = kicking the ball between the uprights.precision = kicking the ball between the uprights and

each kick travels the same path.**precision depends on more than one measurement**

Scientific Notation

• Chemistry involves very small and very large numbers.– Example: 1 gram of Hydrogen =

301,000,000,000,000,000,000,000 hydrogen molecules. This is a long number to write.• Use scientific notation:

– 36,000 is written 3.6 x 104 (3.6 x 10 x 10 x 10 x 10)

• If it’s a small number such as .00036 use scientific notation:– .00036 is written 3.6 x 10-4

Multiplication/Division/Addition/Subtraction

• Mathematics Review (pg. 31)

Significant Figures

• = include all the digits that are known precisely plus one last digit that is estimated.– Write down 1-6 on pg. 33 in your book– Do pg. 34, #7 a-f