1. Using Scientific Measurements
Chapter 2
Section 3

2. Accuracy vs. Precision
_______________: the closeness of measurements to the correct or accepted value of the quantity measured
______________: the closeness of a set of measurements of the same quantity made in the same way

3. Accuracy vs. Precision ___________________ ____________________
_____________________
_______________________

4. Percent Error
________________is calculated to help determine the validity of your data
Percent error=
Sometimes the value is ____________, sometimes ___________, so usually the ____________________is used

5. Reading Instruments
For a ___________device, the rule is to estimate ________________________
_____________________of the device.
For a digital device, the rule is to __________________________________

6. Measuring Rules
_____

7. Digital Device
You can report all the digits displayed which is __________g.

8. Significant Figures
_____________________: any digit in a measurement that is known with certainty
This includes any estimated digit from a non-digital scale
There is a system for determining the number of “sig figs” you are given a measured quantity

9. Use the Map and the Rules

10. Rule 1
If a decimal is present in the measured quantity, start from the ___________________ of the number
Move across the number until you get to the first nonzero digit
Count it and all the rest
Example: m has 3 sig figs

11. Rule 2
If a decimal is absent, start from the ____________________of the number
Move across the number until you get to the first nonzero digit
Count it and all the rest
Example: 55,240 g has 4 sig figs

12. Practice: How many sig figs?
3440. cm
910 m L kg

13. Significant Figure: Rules for Calculations
Multiplication and Division Rule:
In multiplication or division, the result carries the same number of significant figures as the factor with the _______________________________.

14. Rules for Calculations
Addition and Subtraction Rule:
In addition or subtraction, the result carries the same number of decimal places as the quantity with the __________________________
It is helpful to draw a line next to the number with the fewest decimal places. This line determines the number of decimal places in the answer.

15. Rules for Calculations
Rules for Rounding:
When rounding to the correct number of significant figures,
round down if the last (or leftmost) digit dropped is ________________;
round up if the last (or leftmost) digit dropped is ___________________.

16. Round to two significant figures: 5.37 rounds to ____
Rules for Rounding
Round to two significant figures:
5.37 rounds to ____
5.34 rounds to ____
5.35 rounds to ____
5.349 rounds to ______
Notice in the last example that only the last (or leftmost) digit being dropped determines in which direction to round—ignore all digits to the right of it.

17. Exceptions
___________________________are not considered for significant figure calculations

18. Scientific Notation
Numbers are written in the form of M x 10n where 1 ≤ M >10 and n is a whole number
Scientific notation is used to exactly show the number of sig figs
It is also used to easily calculate very large or very small numbers

19. Rules for Scientific Notation
Determine M by moving the decimal point in the original number to the left or right so that only one nonzero digit remains to the left of the decimal point
Determine n by counting the number of places you moved the decimal point
If you moved it to the left, n is positive; to the right, n is negative

20. Scientific Notation, Continued
There are 26,800,000,000,000,000,000,000 helium atoms in 1.00 L of helium gas. Express the number in scientific notation.
The typical length between a carbon and oxygen atom in a molecule of carbon dioxide is m. What is the length expressed in scientific notation?

21. Direct Proportions
Two quantities are directly proportional to each other if dividing one by the other gives a ________ value
or ____________
See the next page for a graph showing this type of relationship

22. Graph of Direct Proportionality

23. Inverse Proportions
Two quantities are inversely proportional to each other if their ____________is constant
_____________
See the graph on the next page

24. Graph of Inverse Proportionality