Name _____________________________ Period___
Chemistry 2011

Scientific Method and Measurement

Definition of Chemistry-

I. Scientific Method A. Steps 1. Observations: i. Use ___________________ senses ii. Good observers see only ___________________________

• Inference- _____________ based on observations (__________________________)

o Example: ▪ Observation – it is cloudy and dark outside ▪ Inference – ______________________________

i. qualitative data –

ii. quantitative data –

1. Hypothesis – possible ____________ to a question or problem; an educated guess based on knowledge and experience; o a ____________ solution o Not in the form of a ___________ but rather ________________ to a question. o Not an ______________.

• Which of the following is considered a hypothesis? o Acid rain will make plants grow shorter. ___________________ o The alligators at the zoo love it when Cindy sings to them.______________ o If I take two aspirin then my headache will go away. __________________ o Why do dogs love treats? ___________________ o The clouds are beautiful when the sun shines through them at sunset. ____

3. Perform an ________________ -

i. Control - ______________________, used for comparison if the experiment produced results.

Practice:

ii. Variables-

a. Independent variable –

b. Dependent variable –

4. Results: Presenting Data 1. Data table – _______________________ of observations in __________ form

2. Graph – ________ display of the relationship between the ___________ and ________________ variables.

a. Y axis – b. X axis –

3. Types of graphs a. Bar Graph - ________________

b. Line Graph - _________________

c. Pie or Circle Graph - ____________

5. Conclusion

a. Revise the hypothesis –

b. Form a _________ -

6. Scientific Law -

II. Scientific Measurements

Measurements

Significant Figures –

ex.

Rules for Determining # of Significant Figures

Look for a decimal point ... is it Absent or Present?

Once you decide the direction to move, start counting at the 1st non-zero digit and count EVERY number afterwards.

Practice: 65000 0.00005

1.0040 0.00341

40300 200300

5.300 x 10 -4 870

Operations with Sig Figs

Adding/Subtracting – arrange numbers in ______________________________. Retain no column that is to the ____________________________________________________________

___________________________ (think _______________________)

Practice: 2.43 cm + 21.1 cm

27.789 m + 6.1 m

87 mL + 11.87 mL

Multiplying/Dividing – answer should have _____________________________________________________
____________________________________________________________

_____________________________

Practice: 5.12 m x 223 m =

4.750 g x 2.00 g =

2.483 m ( 0.52 s =

Combining Operations – observe the “_______________________________________” (________________) when considering sig. figs. You will have to determine sig. figs. for each step

Practice: (2.3 cm + 4.37 cm) x 38.2 cm

62.2 m ( 2.0 s + 47.3 m/s

III. Scientific Measurements

Why are sig figs important? ... ____________________________________________________________

____

Precision – ____________________________________________________________

____________________

Accuracy – ____________________________________________________________

___________________

Example: Jennie massed a 100-g object. Her 1st measurement was 175.6 g and her 2nd measurement was 175.3 g. Were her measurements accurate or precise?

IV. Scientific Notation

Why is it used? ... ____________________________________________________________

_______________

general formula: for very large numbers, n is ________________ for very small numbers, n is ________________

Ex. mass of proton:
0.000 000 000 000 000 000 000 000 001 672 62 kg

Note: # of sig figs ___________________________________ when converting to/from scientific notation

Ex. 0.0000018 km = 7.8 x 10 5 mm =

231,580,000 s = 1.505 x 10 –3 kg =

0.670005 cm = 9.23 x 10 2 m =

To key in scientific notation in calculator ( _______________________________________

|Prefix |Symbol |Factor |Scientific notation |Example |
|kilo | | | | |
|hecto |h |100 |102 |hectometer (hm) |
|deca |da |10 |101 |decaliter (daL) |
|BASE |meter, liter, grams| | | |
|Unit | |1 |100 |meter, liter, grams |
|deci |d |1/10 |10-1 |deciliter (dL) |
|centi | | | | |
|milli | | | | |
|micro |( |1/1 000 000 |10-6 |microgram ((g) |
|nano |n |1/1 000 000 000 |10-9 |nanometer (nm) |

V. Metric System Conversions

Note: The power of 10 is attached to the plain g, m, or s. For example, 1 kg = ________ and 1 mm = ______

Example 1: Convert 26.4 kg to grams. Example 3: Convert 0.0035 ms to s.

Example 2: Convert 2004 m to cm. Example 4: Convert 8.805 kg to dg

VI. Conversions

Use dimensional analysis - - -

Example 1: Convert 2.4 days to seconds.

Example 2: How many inches are in 2.5 miles?

Example 3 : Eggs shipped to market are packed 12 eggs to 1 carton and 20 cartons to 1 box. A crate holds 4 boxes. Crates are stacked on a truck 5 crates wide, 6 crates deep, and 5 crates high. How many eggs are shipped in 5 truckloads?

ratios:

1. Multiple step problems

a. 550 meters per sec = __________ kilometers per min

b. If the cafeteria serves 308.76 lb of hamburger meat per month, convert this to kg per year.

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Ex. The diagram shows different setups of an experiment to determine how sharks find their prey. Which experimental setup is the control?

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