Chemistry and the Scientific Method
Home > Flashcards > Print Preview
The flashcards below were created by user
on FreezingBlue Flashcards
. What would you like to do?
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
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
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
What are SI units?
- Systeme Internationale
- Based on Metric System
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
- How close to "correct" value.
- Trying to measure a standard.
- Calculated by Errors.
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 %
- 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
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
What are Leading zeros?
- Come before non-zero digits
- They NEVER count
- Ex: 0.00037
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
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
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
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
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
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
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
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
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)
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
What would you like to do?
Home > Flashcards > Print Preview