Exam One

Scientific Method
1) Question/Hypothesis (2) Method/observations/experiment (3) data (4) conclusion/discussions
Matter
matter is classified into elements, compounds, and mixtures
Changes in matter–physical
this would be something like breaking a stick
changes in matter–chemical
a chemical change in matter involves a chemical reaction. (ie-dissolving salt in water); a chemical change results in the identity and characteristics of matter changing (ie-metal rusting)
Characteristics of elements in the periodic table
*metals are to the left of the staircase; nonmetals are to the right *rows=periods *columns=families *column 1 is the alkaline metals; column 2 are the alkaline earth metlals; *8a are the noble gases *7a are the halogens
naming compounds
first element is named normal;
Law of conservation of matter and mass
this law says that in a chemical reaction, all matter is conserved; anything on the reactant side must be on the product side; you may need to add coefficients to balance the chemical equations
chemical equation
involves a reactant and a product: [reactant]—>[product]; IE–C + O—> CO2
not necessarily conserved in an equation
*the # of molecule of reactants may/may not be equal # of molecules of products; (same for volume of reactants/products)
heterogeneous mixture
when the composition is not the same throughout the sample (ie-granite)
homegeneous mixture
the composition is uniform throughout the sample (ie–honey)
Density
D=mass/volume
metalloids
5,14,32,33, 51, 52, 84
atomic number
The number of protons always equals the number of electrons in an atom, and that number is equal to the atomic number. For instance, carbon has an atomic number of six and therefore has six protons and six electrons.
atomic mass
The atomic mass is the sum of the protons and neutrons in the nucleus**************
Atomic Mass = # Protons + # Neutrons
The atomic mass of carbon = 12
The atomic # of carbon = 6 = the # of protons
# neutrons = Atomic Mass – # protons
# neutrons =12 – 6 = 6
valence electrons
outer electrons (= to the # at the top of the periodic table–column); elements 21-30 dont have specific valence electrons
isotopes
Atoms of the same element can have different numbers of neutrons; the different possible versions of each element are called isotopes. For example, the most common isotope of hydrogen has no neutrons at all;
covalent bonds
Covalent bonds are forces that hold atoms together. The forces are formed when the atoms of a molecule share electrons.
octet rule
if we get 8 electrons around an atom somehow, then it is stable
duet rule
applies to all atoms that only need to fill “s” orbitals upon bonding. (the Hydrogen atom only needs 2 electrons at all times)
the lewis structure
diagram showing shared and unshared pairs of electrons in an atom, molecule, or ion.
Global warming/greenhouse effect
it is in increase in the near surface temp of the Earth; it refers to the warning predicted to occur as a result of increased emissions from greenhouse gases; these gases are responsible for trapping heat and not letting it escape into the atmosphere; this will lead to a gradual increase of temperature over time
greenhouse gases
CO2, H2O, CH4, N2O (exist naturally, but also emitted by human activity/fossil fuels)
infrared radiation
Infrared rays thus occupy that part of the electromagnetic spectrum with a frequency less than that of visible light and greater than that of most radio waves, although there is some overlap. The name infrared means “below the red,” i.e., beyond the red, or lower-frequency (longer wavelength), end of the visible spectrum. Infrared radiation is thermal, or heat , radiation.
UV radiation
Ultraviolet (UV) radiation is defined as that portion of the electromagnetic spectrum between x rays and visible light, i.e., between 40 and 400 nm (30–3 eV). The UV spectrum is divided into Vacuum UV (40-190 nm), Far UV (190-220 nm), UVC (220-290 nm), UVB (290-320), and UVA (320-400 nm). The sun is our primary natural source of UV radiation
microwaves
cause molecules to spin, which causes friction, which leads to heat
VSEPR theory
Lewis structures can be used to predict the 3-dimensional shape of a molecule by using a simple theory known as VSEPR: Valence Shell Electron Pair Repulsion
We know that electrons repel each other, since they have like charges. VSEPR theory states that the electrons in a molecule repel each other, so the orbitals containing those electrons are oriented as far away from each other as possible.
bent molecule
H20
linear molecule
Cl2
trigonal planar molecule
BF3
trigonal pyramidal molecule
NH3
tetrahedral molecule
CH4
Role of Infrared Radiation in Global warming
IR is responsible for making the greenhouse gases vibrate which means they absorb the IR radiation and re-emit it back to the earth. So heat is trapped in the atmosphere and can’t escape to space. The vibrations are like a dog’s tail wagging. Diatomic molecules can vibrate, but they can’t wag so therefore they don’t trap the IR and thus heat in the atmosphere.
diatomic molecules
2 atomed molecules
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