
9/16/03
Chemistry Review
Part I: Book Review
Chemical- Any substance with a definite composition
Physical states
Solid- Fixed volume and shape
Liquid- Fixed volume and variable shape
Gas- Variable volume and gas
Decomposition- One reactant breaks into two products
Activation energy- needed to start reaction (not always needed)
Exothermic reaction (hot)- releases energy
Endothermic reaction (cold)- absorbs energy
Matter- anything that has mass or volume
Mass- quantity of the matter in an object
Weight- the force produced by gravity acting on mass
Newtons- the unit of force
Qualitative terms- descriptive terms- light, heavy, large, etc.
Quantitative terms- numbers and units
SI units- K h dK d c m
Derived units- combining several base units ex.- D= m/v
Physical property- can be measured without changing chemical nature
Physical changes- can occour without changing chemical nature
Chemical change- substances turning into new substances
Evidence of a chemical change:
Evolution of a gas
Formation of a precipitate
Evolution or absorption of heat
Emission of light
Color change
Nature of matter:
111 different elements
90% atoms are hydrogen
70% mass Earth’s crust is oxygen and silicon
Life: carbon, hydrogen, oxygen, nitrogen
Allotrope- different molecular forms ex. 02 and 03
Classification
Compound- pure substance with atoms from two or more different elements
Covalent compounds- neutral
Ionic compounds- have electrical charge
Acid Base
Sour Bitter
PH less than 7 pH greater than 7
React with bases and metals to form salts React with acids to form salts
Organic compounds have carbon
Formulas
Molecular formula ex. C9H8O4
Structural formula
Ball and stick model
Space-fill model
Mixture- Two or more pure substances mixed together
Homogeneous mixture- Uniform distribution
Heterogeneous mixture- Uneven distribution
Mixtures vs. Compouns
1. Mixtures are like substances it contains, but compounds often don’t resemble contents
2. Compounds have definite composition by mass. Mixtures can vary in proportion
Purity (Best-Worst)
1. Primary- standard-grade
2. Reagent- grade
3. Commercial/tech grade
Chemical energy- matter possesses it because of chemical makeup
Chemical bond- force of attraction
Kinetic energy- due to motion
Potential energy- position to other objects
Energy- capacity to do work
Law of conservation of energy- energy can be neither created not destroyed
Heat- total of kinetic energy
System- all components being studied
Temperature- average kinetic energy of random motion of particles in a substance
Zero degrees Kelvin = 273.15 degrees Celcius
Specific heat capacity- amount of energy needed to raise the temperature of 1g of substance by 1k. Expressed in (J/gK)
SI unit of energy- Joule, J
E= mc squared- Law by Albert Einstein 1905. Says energy = mass x (speed of light in a vacuum) squared
1 Joule is 1Kg m2/s2
Polymer- long chain
Hypothesis- reasonable, testable explanation
Theory- broad, generalization based on observation, experimentation and reasoning
Scientific law- statement/mathematic expression that are consistently true
Law of Conservation of Mass- Product mass= reactant mass
Accuracy- how close to true value
Precision- how close several measures of some quantity agree
Part II: Notes
Quantitative research- Controlled experiments that result in numbers
Data collection- tables
Descriptive research- Observational data. No number values- just senses (smell, color, etc.)
Scientific Method- A systematic approach to problem solving. There is no ONE scientific method
Hypothesis- educated guess
Theory- Most logical explanation after testing
Law- A generally accepted theory (many trials)
Dependant variable- condition that is observed (results)
Density measures the mass in a given volume of a substance. Density is the ratio of two measured properties of matter; mass and volume. D= m/v
Density is a derived unit (need to calculate with two other units)
The density of a pure substance is a constant. Density can help you identify unknown substances
Water has a density of .99820 g/cm3 at 20degrees Celcius (most give water a density of one)
Accuracy- how close the measurement is to the actual value
Accuracy can be true of an individual measurement or the average of several
Precision- how well the measurement can be repeated Precision requires several measurements before anything can be deduced