Important Chemistry Concepts for Nursing School Entrance Exam Study Guide
Concepts You Should Be Familiar With
- The Scientific Method
- The Science of Chemistry
The scientific method is based upon observations that lead to the formulation of a hypothesis in an attempt to make a comprehensive guess. Only experiments (reproducible ones) will confirm the hypothesis and develop into a theory supported by all the facts.
Chemistry is the study of the structures, properties, and transformation of atoms and molecules.
- Metric System
Metric system is the standard system for recording measurements. It is a decimal system (the basic unit and its subunits are separated by increasing and decreasing powers of ten). Some of the basic units of measurement are:
- Length: meter (m)
- Volume: liter (l)
- Mass: kilogram (kg)
- Time: the second (s)
- Temperature: Kelvin (° K)
- Amount of substance: mole (mol)
Conversion factor establishes a relationship of equivalence in measurement between two different units. It is expressed as a fraction. For instance, for 1 kg = 2.2 lb., the conversion factor is: or .
Convert 50 cm to m:
Since 100 cm = 1 m, the conversion factor is or
So, 50 cm × () = 0.50 m
How many grams are in 0.45 lbs.? (1 lb. = 453.6 g)
Conversion factor: or
Since we need an answer in grams, we will use the conversion factor that has the grams in the numerator.
So, 0.45 lb. × () = 204.1 g.
The number of significant figures in any physical quantity or measurement is the number of digits known precisely to be accurate. The last digit to the right is inaccurate. The rules for counting significant figures are the following:
- Zeros sandwiched between nonzero digits are significant figures. For example, both 400.005 and 400,005 have six significant figures.
- Zeros that locate the decimal place (place holder) on the left are not significant. For example, 0.045 ml, 0.0045 ml, and 0.00045 ml each have two significant figures.
- Trailing zeros to the right of the decimal point are significant if the number is greater than 1. For example, 4.56000 has six significant figures.
- For numbers smaller than 1, only zeros to the right of the first significant digit are significant. For example, 0.020 has two significant figures.
- Trailing zeros are not significant in a nondecimal number. For example, 5,500 has two significant figures.
Error is the difference between a value obtained experimentally and the standard value accepted by the scientific community.
Accuracy establishes how close in agreement a measurement is with the accepted value.
Precision of a measurement is the degree to which successive measurements agree with each other (average deviation is minimized).
Uncertainty expresses the doubt associated with the accuracy of any single measurement.
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