1. Scientific Measurement
Chapter 3

2. Qualitative Measurements descriptive non-numerical
Quantitative Measurements: definite, with numbers & units
SI Units are used in science
based on the metric system

3. Accuracy, Precision & Error
Accuracy is a measure of how correct a measured value is or how close to the actual value
Precision is a measure of how reproducible a value is or how close a series of measurements are to one another – for a single value, it depends on the instrument used

4. Percent Error is more useful than error, it is the relative error
Error is the difference between the measured (experimental) value & the true (accepted) value
Error = accepted value – experimental value
Percent Error is more useful than error, it is the relative error
% Error = (error / accepted value) x 100%
% Error is an absolute value (always positive)

5. International System of Units (SI Units)

6. More convenient unit in everyday life is liter (L)
Length – base unit is the meter (m)
Volume – derived unit, derived from length – cubic meter (m3)
More convenient unit in everyday life is liter (L)

7. Mass – base unit is kilogram (kg)
More commonly used unit is gram (g) = 1/1000 of a kg
Density – ratio of an objects mass to its volume

8. Density generally decreases as the temperature increases
Temperature – determines the direction of heat transfer
Heat moves from the object with higher temperature to the object with lower temperature

9. Celsius – basis is the freezing point of water and the boiling point of water
Freezing point = 0oC
Boiling point = 100oC
Kelvin – basis is absolute zero – no movement occurs, no NRG
Freezing point water = 273K
Boiling Point water = 373K
0K = absolute zero (theoretical)

10. K = oC + 273
oC = K – 273
oF = 9/5(oC) + 32
oC = 5/9(oF – 32)

11. Simple Metric Conversions
Metric System uses prefixes to denote larger or smaller units
Kilo (k) – 1000 times bigger
Hecta (h) – 100 times bigger
Deca (da) – 10 times bigger
Deci (d) – 10 times smaller
Centi (c) – 100 times smaller
Milli (m) – 1000 times smaller

12. Simple Metric Conversions
You multiply by the power of 10 when you are going to smaller units
5kg = 5000g
You divide by the power of 10 when you are going to larger units
3000mm = 3m

13. Practice Problems
1. How many g is 56dg?
2. How many L is 8.2kL?
3. How many m is 0.76hm?
4. How many L is 14.3mL?
5. How many dag is 450g?
6. How many m is 2300cm?

14. Scientific Notation Used to write very big & small numbers in science
A coefficient and 10 raised to a power
Example: is written as 4.5x104
Example: is written as 4.5x10-4

15. To figure out how to write a number in scientific notation:
Move the decimal point to left or right, until only 1 number is to the left of the decimal point
Count the spaces you moved the decimal point – this is the exponent on the 10

16. If you moved the decimal point to the left, your exponent is positive
If you moved to the right, your exponent is negative
The coefficient is always a number greater than or equal to 1 and less than 10

17. Significant Figures What is the difference between these numbers? 4.5
4.50
And what about these?
450
450.00

18. Significant Figures
The difference between the numbers is that one is more certain than the other, even though the mathematical values are the same.
Significant figures in a number tell you how certain you are about that measurement.
Here are the rules:

19. Any non-zero digits are significant
Zero’s between 2 non-zero digits are significant (101)
Leftmost zero’s, in front of a non-zero digit are NOT significant (0.002)

20. 4. Zeros at the end & to the right of a decimal point are always significant (45.00)
5. Rightmost zeros without a decimal are not significant (4500)
6. Counting & exact definitions have UNLIMITED sigfigs! (60min = 1hr)

21. How many SigFigs? cm
10 apples
200 m

22. Calculating using SigFigs
After any calculation, your answer must not be any more certain than the least certain value you stared with.
For multiplying and dividing, you must round to the least number of sigfigs
For adding and subtracting, you must round to the least number of decimal places
Round last to make sure your answer is as accurate as possible

23. Calculate the answers, using the correct # of sigfigs:
Example
Calculate the answers, using the correct # of sigfigs:
7.9 * 2 = 20 (1 sigfig)
7.9 * 2.0 = 16 (2 sigfigs)
7.90 * 2.00 = 15.8 (3 sigfigs)