1. Chapter 1 and 2 Scientific Method and Measurement
Chemistry
Chapter 1 and 2
Scientific Method and Measurement
Vocabulary Headings Important Info

2. Distinguish between a scientific law and a scientific theory.
Observation of a natural event
Summary of what occurs
Does not try to explain why something occurs only tells what occurs
Scientific Theory
Explanation of events
Tries to explain why something occurs
Supported by several experiments
Must be able to predict what happens by using the theory

3. Explain and apply the steps of the scientific method.
Observation
Seeing something that makes you ask a question
Formulate a question
What exactly do you want to learn?
Research the question
Find out what others have said about your question
Develop a hypothesis
Use the information you found in research to develop an educated guess in answer to your question
Experiment/Collect Data
Test only one variable at a time
Use a control
Control is a version of the experiment where nothing is changed
Draw conclusions
Analyze the data
Did the data support your hypothesis?

4. Describe the relationship between pure science and technology.
Pure science studies things that may never be useful
Pure science seeks only to know
Technology is useful
Technology is applied science
Studying far off galaxies is pure science
Creating a vaccine for a disease is technology

5. Distinguish between an independent and dependent variable.
Independent variable
The variable that you change in the experiment
If you place one plant in the window and one in the closet the variable you are changing is the amount of light
Amount of light would be the independent variable
Dependent variable
The variable that changes because of the change in the independent variable
The plant in the closet is only 6 cm tall. The plant in the window is 12 cm tall.
Height of the plant would be the dependent variable.

6. Identify the SI base units and compare the base units to derived units.
Quantity
Unit
Abbreviation
Length
Meter m
Mass
Kilogram kg
Time
Second s
Temperature
Kelvin K
Electric current
Ampere A
Amount of substance
Mole
mol
Luminous intensity
Candela cd

7. Identify the SI base units and compare the base units to derived units
Derived units are made up of more than one base unit
Examples of derived units : g/cm3, g/mol, m3
If it is not on the list of base units, it is a derived unit.

8. Define the main prefixes used in the metric system.
Symbol
Meaning
Multiple of base unit
Deca da
Ten 10
Hecto h
Hundred
100
Kilo- k
Thousand
1000
Mega- M
Million
Giga- G
Billion

9. Define the main prefixes used in the metric system.
Symbol
Meaning
Multiple of base unit
Deci- d
Tenth
1/10
Centi- c
Hundredth
1/100
Milli- m
Thousandth
1/1000
Micro-
Millionth
1/1,000,000
Nano- n
billionth
1/1,000,000,000

10. Convert between different metric units.
G _ _ M _ _ k h da (base) d c m _ _ m _ _ n
Start to the right of the given
Move the decimal to the right of the unknown
Add zeroes to hold the decimal place
2km = ____________ cm
Move from the right of the k to the right of the c
5 spaces to the right, need 5 zeroes to hold the place
2km = 200,000cm

11. Convert the following measurements
6.7 nm = ________m
37 kg = ________cg
23 ml = ________ kl
9.7 dam = ______m
cg = _____mg
0.5 cm = _______mm
0.68 Mg = _______cg
1Gm= _________nm
300 mm = _______m
2 km = ________hm
0.90 cm = ______mm
5.67 dm = ______km
3.6 Gm = ________m
4.5 mg= _________g
34 kg = ________mg
45 ms = ________s

12. Solve density problems.
Density is the Mass divided by the Volume
D = M/V
The equation can be rearranged to solve for any of the three variables.
M = D x V
V = M/D
Example
A block of aluminum occupies a volume of 15.0 mL and weighs 40.5 g. What is its density?
M = 40.5 g
V = 15.0 mL
D = M/V D = 40.5g/15.0 mL D = 2.7 g/mL

13. Density Problems cont.
What is the weight of the ethyl alcohol that exactly fills a mL container? The density of ethyl alcohol is g/mL.
D = g/ml (3 sig figs)
V = mL (4 sig figs)
M = D x V M = 0.789g/ml x mL
M = 158 g (3 sig figs)

14. Density Problems cont.
What volume of silver metal will weigh exactly g. The density of silver is 10.5 g/cm3.
D = 10.5 g/cm3
M = g
V = M / D V = g/ 10.5 g/cm3
V = 238 cm3 (3 sig figs)

15. Density Problems cont.
A rectangular block of copper metal weighs 1896 g. The dimensions of the block are 8.4 cm by 5.5 cm by 4.6 cm. From this data, what is the density of copper?
First calculate the volume. (V = l x w x h)
V = 8.4 cm x 5.5 cm x 4.6 cm V = cm3
There are only 2 sig figs in the problem so you must round to 210 cm3
Now calculate the density.
M = 1896 g
V = 210 cm3
D = M/V D = 1896 g/ 210 cm3 D = 9.03 g/cm3
Can only have 2 sig figs therefore the answer would be 9.0 g/cm3

16. Density Practice
Mercury metal is poured into a graduated cylinder that holds exactly 22.5 mL. The mercury used to fill the cylinder weighs g. From this information, calculate the density of mercury.
A flask that weighs g is filled with 225 mL of carbon tetrachloride. The weight of the flask and carbon tetrachloride is found to be g. From this information, calculate the density of carbon tetrachloride.
Calculate the density of sulfuric acid if 35.4 mL of the acid weighs g.
Find the mass of mL of benzene. The density of benzene is g/mL.
A block of lead has dimensions of 4.50 cm by 5.20 cm by 6.00 cm. The block weighs 1587 g. From this information, calculate the density of lead.
What is the volume of a substance with a mass of 0.35 g and a density of 0.9 g/ml?

17. Use scientific notation to represent very large and small numbers
3.75 x 108
Scientific Notation
only one number allowed in front of the decimal
8 is called the exponent
If the exponent is positive, move the decimal to the right the same number of times as the exponent
If the exponent is negative, move the decimal to the left the same number of times as the exponent
375,000,000 is the number above written in standard format

18. Use scientific notation to represent very large and small numbers
Only 1 number allowed in front of the decimal
Count the number of times the decimal must be moved this number becomes the exponent
If the original number is larger than one the exponent is positive
3.0 x 108
If the number is smaller than one the exponent is negative
3.0 x 10-8

19. Write the following numbers in scientific notationkg L m km kg
atoms

20. Write the following numbers in standard form
4.5 x 105
7.009 x 109
4.6 x 104
3.2 x 1015
3.115 x 10-8
6.05 x 10-3
1.99 x 10-10
3.01 x 10-6

21. Distinguish between accuracy and precision.
Precision is how close two measurements are to each other.
1.45 and 1.44 are precise
Accuracy is how close a number is to an accepted value.
If the accepted value is 9 then the above numbers are not accurate.

22. Accuracy and Precision
Numbers may be:
Accurate only
At least one of the numbers is close to the accepted values, but not close to the other measurements
Precise only
The numbers are close to one another but not to the accepted value
Accurate and precise
The data is close to one another and close to the accepted value
Neither accurate nor precise
The data is not close to the other measurements nor to the accepted value

23. Precision or Accuracy?

24. Define significant figures and know when to use them.
When numbers are measured, measurements are always taken to the first number that is estimated (guessed).
This is the last significant figure.
If the measurement is 100, the actual number could be anywhere from
If the measurement is then it can only vary from 99.5 and
Significant figures indicate precision of measurement.

25. Use significant figures in problem solving.
If the decimal is present come in from the pacific to the first nonzero number (1-9) and count all remaining numbers left to right.

26. Use significant figures in problem solving.
If the decimal is absent come in from the Atlantic to the first nonzero number (1-9) and count all remaining numbers from right to left.

27. Use significant figures in problem solving.
The answer to a problem cannot have more significant figures than the number in the problem with the fewest significant figures.
Once the correct number of significant figures has been reached, zeroes are used as place holders
written in 3 significant figures would be
Cannot drop the zeros. You wouldn’t want me to pay you 10 dollars if I owed you Dropping zeroes changes the value of the number. Round then hold the place with zeroes to keep the value the same.
If the number following the last significant figure is 5 or greater the last significant figure goes up one.
If the number following the last significant figure is 4 or less the last significant figure stays the same.

28. Determine the number of significant figures in each of the following:
1.560
1560
300000
100
100.0

29. Round the following to 3 significant figures:
4.900
4.905
20087
653456
928227
5.596
300.0 (try scientific notation)

30. Lab Equipment Erlenmeyer Flask Graduated Cylinder Triple Beam Balance
Watch glass
Beakers
Volumetric Flask

31. Lab Equipment Test Tube Holder Test Tube Rack Test Tubes
Crucible Tongs
Bunsen Burner
Crucibles