# 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 + # NeutronsThe atomic mass of carbon = 12The 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 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.
 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 RepulsionWe 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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