# Chemistry and the Scientific Method

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1. What are the steps in the Scientific Method?
• Observation: .
• Hypothesis: Working model
• Test: Hypothesis has to be consistent with observations
• Theory: Based on common principles, reason, logic, math
• Test/Experimenting: .
• Laws: Developed from theories. Until someone else makes a different observation
2. What are the two different types of Observations?
• Qualitative: What color is it? Smell? Liquid? Etc. No numbers. Usually in chemical reactions.
• Quantitative: Numerical part/Measurement
3. What are quantitative observations?
• Numerical part/Measurement
• Has Dimensions or Units
• Can mult/div, CAN'T add/subt quantities with different units
• Ex: 25.35 g ; 2 ft x3 ft = 6 "squared feet" --> 6 ft^2
4. What are SI units?
• Systeme Internationale
• Based on Metric System
5. What are the SI units of Length, Mass, Time, Temperature, Energy, Volume?
• Length: meter (m)
• Volume: cubed meters (m^3)
• Mass: kilogram (kg)
• Time: second (s)
• Temp: Kelvin (K) = C + 273.15
• ANY Energy (SI): Joule (J)
• Heat Energy (Metric): Calorie (cal) = 4.184 J
6. Define Accuracy.
• How close to "correct" value.
• Trying to measure a standard.
• Calculated by Errors.
7. Define Error, Difference Error, and Percent Error.
• Error: Difference between your measurement and real value
• Ex: My measurement: C = 2.375x10^8 m/s Real: 2.998x10^8 m/s (speed of light)
• Difference Error: 0.623x10^8 m/s
• Percent Error: = (|Diff Error|/Correct) x 100
• Ex % Error: = (0.623x10^8 m/s)/(2.998x10^8 m/s) x 100 = 20.8 %
8. Define Precision.
• How repeatable/reproducible a measurement is.
• Ex: 24.275 g ; 24.286 g ; 24.279 g ; 24.263 g ; 24.273 g
•        3 digits remain constant, 2 digits vary, first digit to vary is in 2nd dec. place
• # of CERTAIN digits + 1st UNCERTAIN (estimated) digit = # of significant digits
•        4 significant digits
9. How do you find the number of significant digits/figures?
• 1. Scan #'s from L --> R until you reach 1st NON-ZERO digit
• 2. Count the digits
• 3. Watch for TRAILING zeros - Zeros that FOLLOW the non-zero digits
• Ex: 275.25 = 5 sig figs
• Ex: 0.00275.25 = 5 sig figs
10. What are Leading zeros?
• Come before non-zero digits
• They NEVER count
• Ex: 0.00037
11. What are Trailing zeros?
• Zeros following the non-zero digits
• If FOLLOWING the dec. point, ALWAYS significant
• Ex: 25.0 = 3 sig figs, zero is significant
• If BEFORE the dec. point, MAY be significant
• Ex: 250 = 2 sig figs, zero not significant; I know it's 200, not certain if it's 50
• Ex: 250. = 3 sig figs, zero is significant; I know it's 200, know it's 50, not certain if it's 0
12. How would you write 25,000 if you're certain of 20000 and 5000 and 1000's but not 10's?
• 25,000 "4 sig figs"
• Scientific Notation: 2.500x10^4
13. Describe Scientific Notation.
• Convert a number to range between 1 and <10
• Ex: 250. = 2.50x10^2 ; (2) indicates # of dec. moves to the Left
• Ex: 0.00025 = 2.5x10^(-4) ; (-4) indicates # of dec. moves to the right; only 2 sig figs
14. Put these prefixes in order from least to greatest with their powers and symbols: mili, nano, centi, kilo, pico, mega, deci, micro.
• Pico (p): 10^(-12)
• Nano (n): 10^(-9)
• Micro (sexy u, "mu"): 10^(-6)
• Mili (m): 10^(-3)
• Centi (c): 10^(-2)
• Deci (d): 10^(-1)
• Kilo (k): 10^3
• Mega (M): 10^6
15. What are Unit (Conversion) Factors?
• Start with a known relationship and rearrange to make it a ratio.
• Ratios could be each other's inverses
• Ex: 1 ft = 12 in --> (1 ft)/(12 in) = 1 => Converts to ft ; (12 in)/(1 ft) => Coverts to in
• EX: 240 in => ? ft
•        (240 in)/1 x (1 ft)/(12 in) = 20 ft
16. What is Density?
• Ratio of mass to volume of matter
• Density = mass(g)/Volume(cm^3 or mL)
• Ratio of 2 quantities can be used as Unit Factor
17. What are the 2 types of Temperature scales and what do they include?
• Degrees Fahrenheit (F) and Degrees Celsius (C)
• Upper and Lower fixed points
18. What are Upper and Lower Fixed Points (UFP & LFP)? Of Celsius and Fahrenheit?
• LFP: Freezing point of water at 1 atmospheric pressure (atm)
•       C = 0 degrees
•       F = 32 degrees
• UFP: Boiling point of water   "   "
•       C = 100 degrees
•       F = 212 degrees
19. What is 1 division (of C/F)?
• 1 increment (Degree) above the LFP
• 180 div F = 100 div C
•       Conversion factor => (9 div F)/(5 div C)
• Ex: Fries are 425 degrees F
•      1. Subtract 32 (How far above LFP) = 393 div F
•      2. Change to # div C by using conversion factor => 218 div C (degrees C)
20. What are the temperature conversion equations?
• Temp (C) = (5/9)(Temp (F) - 32) => C = (5/9)(F  - 32)
• Temp (F) = (9/5)Temp (C) +32 => F = (9/5)C +32
 Author: Anonymous ID: 194492 Card Set: Chemistry and the Scientific Method Updated: 2013-01-22 21:57:57 Tags: Lecture Chemistry Scientific Method Folders: Description: Lecture 1 Chemistry and the Scientific Method Show Answers: