Basic Chemistry
Essay by 24 • November 10, 2010 • 998 Words (4 Pages) • 1,895 Views
Observing- use of senses to obtain information
-Making measurements and collecting data
-Qualitative-descriptive (ex: color)
-Quantative-numerical (ex: mass)
-System-a specific portion of matter in a given region of space that has been selected for study during an experimentation or observation
Hypothesis- testable statement
-Formed from generalizations about data
-Basis for making predictions
-"If-then" statements: "then" is the prediction that is the casis for testing using an experiment
Theorizing-when data shows a hypothesis is correct you try to explain it by constructing a model
-Model- more than a physical object; it's often an explanation of how phenomena occur and how data or events are related. May be visual, verbal, or mathematical
-If a model explains a phenomena correctly, may become part of a theory
-Theory-broad generalization that explains a body of facts or phenomena
-Theories are successful if they can predict the results of new experiments
Units of measurements- measurements are quantitative, represent quantities
-Quantity- something that has magnitude, sizes, or amounts
-Units of measurement compare what is to be measured with a previously defined size
SI measurment-adopted in 1960
-Has seven base units, most other units are adopted from these seven
-Defined in terms of standards in measurement. Standards are objects or natural phenomena that are of constant value, easy to preserve and reproduce, and practical in size
-International organizations oniter the defining process
-Everything must agreed upon internationally
Seven basic units: Length (l), mass (m), time (t), tempature (T), amount of substance (n), electric current (I), and luminous intensity (Iv)
-Mass-measure of the quantity of measure-standard unit: kilogram
-Weight-measure of the gravitational pull on matter
-Length-standard unit: meter
-Time-standard unit: second
-Tempature-standard unit: kelvin
-Amount of substance-standard unit: mole
-Electric current-standard unit: ampere
-Luminous intensity-standard unit: candela
Derived units- combinations of SI base units
-produced by multiplying or dividing standard units
Some derived units: Area (A), volume (V), density (D), molar mass (m), concentration(c), molar volume (Vm), energy (E)
-Volume-amount of space occupied by an object
-Standard unit: cubic meter
-Density-ratio of mass to volume, or mass divided by volume
-Standard unit: kilogram per cubic meter
-A chacteristic physical property of a substance
Conversion factor-ratio derived from the equality between two different units that can be used to convert from one unit to the other
-Conversion factors always equal 1
-Can derive conversion factors only if you know the relationship between the unit you have and the unit you want
Using scientific measurements- for a reported measurement to be usedful, there must be sime indication of its reliability
or uncertainty
-Accuracy-refers to the closeness of measurements to the correct or accepted value of the quantity measured
-Precision-refers to the closeness of a set of measurements of the same quantity made in the same way
-Percent error-calculated to find out if the accuracy of an individual value or of an average experimental value can be compared quantatively with the correct or accepted value
-Calculated by subtracting the experimental value from the accepted value, dividing the difference by the accepted value, then multiplying by 100
-Positive value if a. value is > than e. value
-Negative value if a. value is < than e. value
-Uncertainty or error always exists
-The skill of the measurer limits the reliablty of results, as do the insturments he uses
-Significant figures- (in a measurement) consists of all the digits known with certainty plus one final digit, which is somewhat uncertain or is estimated
-Insignificant digits are never reported
-If a number contains no zeros, then all digits are significant
-Rules for determining significant zeros:
1.zeros appearing between nonzero digits
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