Chapter 1- Calculations and Measurement Flashcards
Calculations & Measurements
State the SI Prefix Multipliers
What is Precision?
The agreement between replicate measurements.
Example: If 4 bullets land close together but don’t hit the bullet, they are precise but not accurate.
What is accuracy?
The agreement between experimental data and the “true” value.
Example: If one arrow hits 5 inches to the left of a target and one hits 5 inches to the right of a target, they are accurate but not precise.
How can accuracy be improved?
By taking replicate measurements and taking the average
How is accuracy assessed? (What is the formula?)
% error = (measured value - “true” value/”true value) x 100.
How can precision be improved?
Careful lab technique and the use of instruments capable of yielding greater precision.
The more significant figures, the more precise the number is.
How can precision be quantified?
Average = sum of measurements/ # of measurements
Standard Deviation = Square root of: sum(measurements-average number of measurements)/number of measurements-1
True/False- The smaller the ratio of the standard deviation to the average value, the better the precision
True
SI Base Units
Meter- Length
Kilogram- Mass
Kelvin- Temperature
Mole- Amount of material
Length conversion factors
1 inch - 2.54 cm
1 mi - 1.609 km
1 mi - 5,280 ft
Mass Conversion Factors
1 lb = .454 kg / 4.45 N
1 lb = 16 oz
1 oz = 28.35 g
1 grain = 64.80 mg
Volume Conversion Factors
1 L = 1 dm^3
1 gal = 3.79 L
1 mL = 1 cm^3
1 cc = 1 cm^3
What is the difference between specific gravity and density?
Specific Gravity is the ratio between an object’s density and the density of water.
They are numerically equal, but the density is labeled in g/mL and specific gravity has no labels.
How do you calculate the specific gravity?
density of object/density of water
What is the density of water?
1.00 g/mL
