1. Accuracy and Precision

2. Accuracy
Definition: How close a value is to the true or accepted value.

3. Precision Definitions: how close a measurement to each other.
How many places a measurement has past the decimal point (related to significant figures which we will learn about at a later date). The more places past the decimal point, the more precise the measurement.

5. Three main types of error
Systematic Errors (can be accounted for)
Instrument
Faults within the equipment for example equipment that has not been calibrated.
Method
Difference in the method between scientists.
Human
These are specific to the scientist for example lack of ability to see color changes.
Random Error
Cannot be controlled, accidental error

6. Units: In Chemistry we will use metric units
Mass:
grams (g)
Volume:
milliliters (mL) or cubic centimeters (cm3)
Length:
centimeters (cm)
Temperature:
degrees Celsius (oC)

7. Reading Glassware
We always guess one decimal place past what we can see, this is called uncertainty.
For example, if the equipment counts by one’s we would give an answer to the tenths place.

8. Reading Liquids When we read liquids we use the meniscus.
Meniscus – upper curved portion of liquids used for measuring.
Ex.
Meniscus 
 Meniscus

9. Practice Reading Glassware
__________ __________ __________

10. Read the significant figures reference sheet

11. (Write These In Your Notebook)
Significant figures 15
675
0.230
8000 45
0.009
6.90
0.89
0.0800
0.406
506
0.0043

12. Significant figures 34.90 + 0.078 = 5.05 x 23 = 7.09 + 15.987 =
(Write These In Your Notebook)
Significant figures =
5.05 x 23 = =