Keith Baty Whitehouse High School

How close a measurement agrees with a true or accepted value.

How close several trials making the same measurement are to each other. The reproducibility of data. Agreement among a set of data.

Poor accuracy Poor precision Poor accuracy Good precision Good accuracy Good precision

A metal bar about 9.8 inches long has been passed around to several groups of students. Each group is asked to measure the length of the bar. Each group has five students and each student independently measures the rod and records his or her result. Which group has the most accurate measurement? Student Group Student 1 Student 2 Student 3 Student 4 Student 5 Group A Group B Group C Group D Group E101110

A metal bar about 9.8 inches long has been passed around to several groups of students. Each group is asked to measure the length of the bar. Each group has five students and each student independently measures the rod and records his or her result. Which group has the most precise measurement? Student Group Student 1 Student 2 Student 3 Student 4 Student 5 Group A Group B Group C Group D Group E101110

Suppose a ruler is used to measure the length of an object as shown in the figure below.

Similarly, all measured quantities are generally reported in such a way that the last digit is uncertain. All digits in a measurement including the uncertain one are called significant figures.

Counting Significant Figures The following rules can be used to determine the number of significant figures (or digits). All non-zero digits are considered significant. If a zero is between two non-zero digits then it is significant. Leading zeros are never significant. Trailing zeros are only significant if there is a decimal present.

Examples Measured Value # of S. F ?

Exact numbers are considered to have an infinite number of significant figures. For example, if you said, “A is twice (or two times) as large as B”, the number 2 would be exact. Or, if you said “There are 4 quarts in a gallon”, the number 4 would be exact. Exact numbers usually involve counted values or definitions.

Multiplication and division For multiplication and division, the number of significant figures in the answer should be equal to the number of sig figs as the measurement with the least number of SIGNIFICANT FIGURES.

Examples: 3.40 x = round off to 15.5 (3 significant figures)

Addition and subtraction The result should be reported to the same number of decimal places as the least precise measurement (the measurement with the fewest decimal places).

Example: = round off to (Uncertainty in tenths place)

9. The following are placed in a beaker weighing g: g of NaCl, 1.26 g of sand and 5.0 g water. What is the final mass of the beaker? 10. If the beaker containing a sample of alcohol weighs g and the empty beaker weighs g, what is the weight of the alcohol?

meter (m) liter (L) gram (g ) deci (d) 10 dm = 1 m centi (c) 100 cm = 1 m milli (m) 1000 mm = 1 m micro (μ) 10 6 μ m = 1 m nano (n) 10 9 nm = 1 m deka (da) 1 dam = 10 m hecto (h) 1 hm = 100 m kilo (k) 1 km = 1000 m mega (M) 1 Mm = 10 6 m English /Metric 1 in = 2.54 cm 1.06 qt = 1 L 1 lb = 454 g CONVERSION FACTORS

When I say I want to lose weight I should say I want to lose mass. I would weigh less on the moon. The problem is I would look the same in a mirror. I really want there to be less of me not less force of gravity on me

Mass a measure of the amount of matter Weight a measure of the force of gravity on an object Volume a measure of the amount of space an object occupies