1. Chapter 2 Measurements and Calculations

2. Sec 1 Scientific Method
def. a logical approach to solving problems by:
1. observing and collecting data
2. formulating hypothesis
3. testing hypotheses
4. formulating theories that are supported by data

3. 1. Observing and Collecting Data
use of sense to obtain information
making measurements
collecting data: 1. qualitative 2. quantitative

4. Experimenting involves…
carrying out a procedure under controlled conditions to make observations and collect data
To learn more about matter  chemists study systems…
System specific portion of matter in a given region of space that has been selected for studying during an experiment or observation
ex: reaction in test tube test tube and contents form a system

5. 2. Formulating Hypotheses
def. testable statement
basis for making predictions and for carrying out further experiments
“if-then” statements

6. 3. Testing Hypothesis
experimentation that provides data to support or refute hypothesis
controls def. experimental conditions that remain constant
variable def. condition that changes

7. 4. Theorizing
theory def. broad generalization that explains a body of facts or phenomena
ex: kinetic molecular theory particles are always in motion

9. Interpreting Graphs
What is the dependent variable? ______________________________
What is the temperature at 5:00 PM? ______________________________

10. Units of Measurement
Sections 2

11. Units of Measurements using SI
We use measurements to represent quantities. A quantity is something that has magnitude, size or amount.
Le Systeme International de Unites, abbreviated SI, is the single measurement system upon which scientist have agreed.
You will need to know the base units and prefixes on the following 2 slides. They must be memorized!!!

12. Units of Measurement SI Measurements
Quantity
Symbol
Unit name
Unit abbreviation
length l
meter m
mass
kilogram kg
time t
second s
Temperature T
Kelvin K
Amount of Substance n
mole
mol

13. Prefixes for Base Units
Abbrev
Factor
Meaning
Ratio
Giga- G
109
1,000,000,000 meters/1Gigameter
Mega- M
106
1,000,000 meters/1Megameter
Kilo- k
103
1000
1,000 meters/
1kilometer
BASE
100 1
Deci- d
10-1
1/10
1 meter/
10decimeters
Centi- c
10-2
1/100
100centimeters
Milli- m
10-3
1/1000
1meter/1,000 millimeters
Micro- u
10-6
1/1,000,000
1,000,000 micrometers
Nano- n
10-9
1/1,000,000,000
1 meter/ 1,000,000,000 nanometers

14. Mass A measure of the quantity of matter. What it isn’t
Weight (the measure of gravitational pull on matter)
The SI unit for mass is kilogram but the base unit is actually the gram

15. Length A measure of distance
SI unit for length for meter but kilometer is used for longer lengths/distances

16. What unit would you use to measure the length and mass of these items----

17. Derived Units
Formed by combining SI base units through multiplying or dividing standard units
Quantity
Quantity Symbol
Unit
Unit Abbr.
Derivation
Volume V
Cubic meter m3
length X width X height
Density D
Grams per ml
g/ml
mass/volume
Molar Mass M
Grams per mole
g/mol
mass/amount of substance
Density Triangle

18. Volume The amount of space occupied by an object.
We use liter and milliliter for volume, which are actually non-SI units
1 milliliter =1 cm3

19. Volume of an Irregularly Shaped Objects
Ex: Find the volume of a dinosaur?
A. Displacement= the volume of water displaced by the object is equal to its volume

20. Density Density is a measure of compactness
It is the ratio of mass to volume or mass divided by volume

21. A sample of aluminum metal has a mass of 8. 4 g
A sample of aluminum metal has a mass of 8.4 g. The volume of the sample is 3.1 cm3. Calculate the density.

22. What is the volume of a sample of liquid mercury that has a mass of 76
What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given the density of mercury is 13.6 g/mL?

23. Mystery Cubes Density Activity

24. Conversion Factors
Conversion factor is a ratio derived from the equality between two different units that can be used to convert from one unit to the other.

25. 1. How many meters are in a km? 
2. How many grams are in a mg? 
.001 g
3. How many amperes are in a MA? 
1,000,000 A
4. What does the prefix µ mean? 
Micro
5. Convert 61 mA into A. 
.061 A
6. Convert nm into m.  m
7. Convert 5 mol into kmol.
.005 jmol

26. Conversion Factor Problems
Sample and Practice Problems pp
Section Review p. 42

27. Sec 3 Using Scientific Measurements

28. Accuracy and Precision
Accuracy refers to the closeness of measurements to the correct or accepted value of the quantity measured
Precision refers to the closeness of a set of measurement to the same quantity made in the same way

29. Percentage Error
Calculated by subtracting the accepted (theoretical) value from the experimental value, dividing the difference by the accepted (theoretical), and then multiplying by 100.

32. Significant Figures Rules: All nonzero digits are significant
Captive zeros are ALWAYS significant
Leading zeros are NEVER significant
Trailing zeros are significant IF there is a decimal

33. Significant Figures
How many significant figures are there in the following:
g   ______
mm  ______
2900 ft  ______
ft  ______

38. Scientific Notation
Numbers are written in the form M X 10n, where the factor M is a number greater than or equal to 1 but less than 10 and n is a whole number.

39. Using a Calculator for Scientific Notation
When we use a calculator for scientific notation we use the 2ND function button and the , button above the 7. Practice problems— 5.3 X 103 / 3.2 X X 10-6 * 1.34 X 104

40. Direct and Inverse Proportions
Two quantities are directly proportional to each other if dividing one by the other gives a constant value.
y/x = k
Two quantities are inversely proportional to each other if their product is a constant.
y = kx
The value of k is a constant