Chapter 1 Flashcards
Chemistry
The central science
The study of matter; its chemical and physical properties, its chemical and physical changes it undergoes - as matter changes, it gains/loses energy.
Matter
Anything that has mass and occupies space.
Energy
The ability to do work and to accomplish some change.
Mass
The measure of the amount of matter.
The Scientific Method
A systematic approach to the discovery of new information.
Characteristics of the scientific method
Observation Formulation of a question Pattern of recognition Developing theories Experimentation Summarizing information
Data
The individual result of a single measurement.
Results
The outcome of an experiment.
Observation
Detectable phenomena about nature.
Observation leads to facts (data).
Facts
Observations about nature that can be reproduced at will, independent of the particular observer (verified by repeated testing).
Inductive reasoning
Specific –> general
Conclude a generality from a limited number of specific examples.
Leads to either scientific law or scientific hypothesis.
Scientific law
A broad statement summarizing a large amount of related facts.
Summarizes large amounts of scientific data and provide descriptions of natural phenomena.
EX: law of gravity, law of conservation of mass/matter, etc.
Many scientific laws can be stated mathematically.
Lack explanatory character. Laws tell you what will happen under a given set of circumstances, but not WHY.
Scientific hypothesis
A speculative explanation of related facts that can lead to the prediction of future behavior.
Testable explanations of observed data. These hypotheses are tested by designing and performing experiments.
Deductive reasoning
General explanation –> prediction of a testable specific result.
Scientific theory
A well-tested and generally accepted hypothesis that explains natural phenomena.
The best current explanation for natural phenomena.
Always tentative and may change as observations of nature accumulate and change.
Scientific model
Used to help illustrate and explain scientific hypotheses, laws, and theories.
Proporties
Characteristics of matter that scientists can use to categorize different types of matter
Ways to categorize matter…
- by state
2. by composition
3 states of matter
- Gas: particles spread widely, no definite shape or volume.
- Liquid: particles close together, definite volume but no definite shape.
- Solid: particles very close together, definite shape and volume.
Pure substance
A substance that has only one component.
Element or compound.
Element
A pure substance that cannot be changed into a simpler form of mater by any chemical reaction.
EX: hydrogen, oxygen
Compound
A pure substance resulting from the combination of two or more elements in a definite, reproducible way, in a fixed ratio.
EX: salt, water
Mixture
A combination of two or more pure substances in which each substance retains its own identity, not undergoing a chemical reaction.
Heterogeneous or homogeneous.
Homogeneous
Uniform composition, particles are well-mixed, thoroughly intermingled.
EX: air, ethanol in water
Heterogeneous
Nonuniform composition, random placement.
EX: oil and water, salt and pepper.
Physical property
Observed without changing the composition or identity of a substance.
Physical change
Produces a recognizable difference in the appearance of a substance without causing any change in its composition or identity.
Conversion from one physical state to another: melting an ice cube.
Chemical property
Results in a change in composition and can be observed only through a chemical reaction.
Chemical reaction (chemical change)
A chemical substance is converted in to one or more different substances by rearranging, removing, replacing, or adding atoms.
EX: hydrogen + oxygen = water
Intensive properties
A property of matter that is independent of the quantity of the substance
EX: color, melting point.
Extensive properties
A property of matter that depends on the quantity of the substance.
EX: mass, volume.
Units
The basic quantity of mass, volume or whatever quantity is being measured.
A measurement is useless without units!
English system
A collection of functionally unrelated units.
It is difficult to convert from one unit to another.
1 foot = 12 inches = 0.33 yard = 1/5280 miles
Metric system
Composed of a set of units that are related to each other decimally, systematic.
Units relate by a power of tens.
Mass
The quantity of matter in an object.
Not synonymous with weight (weight = mass X acceleration due to gravity).
The standard unit is the gram (g).
Must be measured on a balance (not a scale).
Length
The distance between two points.
Standard unit is the meter.
The yard is the common English unit (1 yd = 0.914 m).
Volume
The space occupied by an object.
Standard unit if the liter.
The quart is the common english unit (1 qt = 0.946 L).
V = L x W x H
V = 1 dm x 1 dm x 1 dm = 1 dm^3 AND 1 dm^3 = 1 L
Significant figures
Information-bearing digits or figures in a number.
All digits in a number representing data or results that are known with certainty plus one uncertain digit - the degree of uncertainty associated with a measurement is indicated by the number of figures used to represent the information.
The measuring device used determines the number of significant figures in a measurement.
How to recognize significant figures…
All nonzero digits are significant.
The number of significant digits is independent of the position of the decimal point.
Zeros located between nonzero digits are significant.
Zeros to the left of the first nonzero integer are not significant (place-holders).
Zeros to the right of the last nonzero digit are significant if the number contains a decimal point.
Zeros to the right of the last nonzero digit in a number that does not contain a decimal point may or may not be significant - it depends on the circumstances.
Zeros at the end of a number (trailing zeros) are…
Significant if the number contains a decimal point. (4.70 = 3 sig figs)
Insignificant if the number does not contain a decimal point. (100 = 1 sig fig)
Scientific notation
Used to express very large or very small numbers easily and with the correct number of significant figures.
Scientific notation rules
To convert a greater than 1 to scientific notation, the original decimal point is moved “x” places to the left, and the resulting number is multiplies by 10^x.
To convert a number less than 1 to scientific notation, the original decimal point is moved “x” places to the right, and the resulting number is multiplied by 10^-x
Accuracy
The degree of agreement between the true value and the measurable value.
Error
The difference between the true value and our estimation.
It may be random or systematic.
Precision
A measure of the agreement of replicate measurements.
Deviation
Amount of variation present in a set of replicate measurements.
Inexact numbers
Have an uncertainty (degree of doubt in final significant digit)
Exact numbers
AKA counted numbers
A consequence of counting.
Has no uncertainty.
Has an infinite number of significant figures.
Rules for rounding numbers
When the number to be dropped is less than 5, the preceding number is not changed.
When the number to be dropped is 5 or larger, the preceding number is increased by one unit.
Significant figures in calculation of results: adding and subtracting rules
The result in a calculation cannot have greater significance than any of the quantities that produced the result.
Significant figures in calculation of results: multiplication and division rules
The answer can be no more precise than the least precise number from which the answer is derived
The least precise number if the one with the fewest significant figures.
Factor-label method
AKA dimensional analysis
Uses conversion factors to convert from one unit to another within the same system and convert units from one system to another.
Convert by writing the data given and multiplying by the conversion factor with the unit of the data given in the denominator.
Temperature
The degree of “hotness” of an object.
The average energy of particles.
Conversions between Fahrenheit and celsius
T/C = (T/F - 32)/1.8 T/F = (T/C x 1.8) + 32
Kelvin temperature scale
A scale that is directly related to molecular motion. As molecular speed increases, the Kelvin temperature proportionately increases.
T/K = T/C + 273.15
Energy
The ability to do work.
Kinetic energy
The energy of motion - energy of action.
Potential energy
The energy of position - stored energy.
Characteristics of energy
Cannot be created or destroyed.
May be converted from one form to another.
Energy conversion always occurs with less than 100% efficiency.
All chemical reactions involve either a “gain” or “loss” of energy.
Categories of enegy
Light Heat Electrical Mechanical Chemical
Units of energy
Calorie or joule (1 cal = 4.18 joules)
Kilocalorie/kcal: food calorie 1 kcal = 1 Calorie = 1000 calories (1 calorie = amount of heat energy required to increase the temperature of 1 gram of water 1 degree Celsius).
Concentration
The number or mass of particles of a substance contained in a specified volume.
Often used to represent the mixtures of different substances.
EX: concentration of oxygen in the air, pollen counts, proper dose of an antibiotic.
Density
The ratio of mass to volume.
d = m/V
An extensive property.
Use to characterize a substance as each substance has a unique density.
Units: g/mL, g/cm^3, g/cc
Anything that has a density less than water will float on water (water = 1 g/mL).
Most to least; mercury, brass, water, cork.
Specific gravity
The ratio of the density of the object in question to the density of pure water at 4 degrees C.
Unitless term because the 2 units cancel.
Health industry uses it to test urine and blood samples.
density of an object / density of water at 4 degrees C
Boiling point of water
373/K
100/C
212/F
Body temperature
310/K
37/C
98.6/F
Room temperature
298/K
25/C
77/F
Freezing point of water
273/K
0/C
32/F
