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Chemistry CHS

for Yasmeen

Area L * W (Length * Width)
Volume L * W * H (Length * Width * Height)this also works for measuring the volume of a cube
Density Mass / Volume.Density is a ratio of mass to volume
µm (micrometers) 1 meter = 1,000,000 µm
water displacement procedure for measuring the volume of an irregular-shaped object. <br> New Volume - Initial Volume (water, no solid) = volume of solid
density of water 1.0 g/cm3 or 1 ml
Change in state solid → liquid → gas.Example: ice cube melts into water, water changes to gas, gas becomes water again.
Physical Change NO new substance is formed
Chemical Change new substance(s) are formed
5 Signs of Chemical Change • Color change <br> • Temperature change <br> • Bubbling – gas is released <br> • Precipitate – solid forms <br> • Light is given off
Malleable verb used to describe materials that are soft and easy to bend or rip
Valence electrons the very last or the very outside electrons of an atom that allow the atom to bond with other atoms to make compounds
Chemical formula Mg + HCl → MgCl + H2 ↑ <br>REACTANTS PRODUCTS <br>(What we start with) (What we end with)
Precipitate particles produced in a chemical reaction that fall to the bottom of a solution (mixture)
Quantitative Observation observing using numbers and measurements
Qualitative Observation observing using descriptions, no numbers needed.
Compound 2 or more DIFFERENT atoms or elements. <br>Ex: H2O, NaCl, H2SO4
Molecule 2 or more atoms. <br>Example: O3, H2O, N2, NaCl, H2SO4
Element is one type of atom. <br>Example: see Periodic Table, approx 117 elements
Pure Substances substances with a definite chemical composition
Heterogeneous mixture particles are NOT equally or evenly distributed <br> Example: Salt and Pepper or Muddy Water
Homogeneous mixtures particles are evenly or equally dispersed or distributed (scattered) <br> Example: solutions such as Kool Aid or Salt Water
Mixtures are not pure substances they do NOT have definite composition.
Filtrate liquid that passes though a filter in a lab experiment
The law of definite proportions States that a chemical compound always contains the same elements are in exactly the same proportions by weight or mass
The law of conservation of mass states that mass cannot be created or destroyed in an ordinary chemical and physical changes.
The law of multiple proportions states that when two elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other in the ratio of small whole numbers
Joseph John Thompson discovered the electron, created the "plum pudding" model of an atom
Democritus ancient Greek that came up with the idea that all matter is made up of invisible atoms
John Dalton revises Democritus’ theory based upon scientific experimentation, didn't know about the existence of subatomic particles
James Chadwick discovered the neutron in 1932
Earnest Rutherford discovers the nucleus in 1909, credited with discovering the proton. He described the atom as electrons that are orbiting around the nucleus like planets orbiting around the sun
the electron cloud the area around the nucleus where you can find electrons orbiting an atom(See page 84, 85, and 88 for pictures)
Isotopes Atoms of the same element that have different numbers of neutrons
Niels Bohr discovered in 1913 that electrons exist in energy levels or quantum levels
Quantum The difference in energy between two energy levels for electrons is known as a quantum of energy
Louis de Broglie discovered that electrons have behavior similar to waves and have certain frequencies which correspond to specific energy levels
Orbitals Regions of the atom where electrons can be found around the nucleus
Electron Clouds another word for orbitals because orbitals don't have well-defined boundaries
Speed of light 2.998 * 10 8 m/s (C)
C (C) is a constant, it stands for the speed of light. <br> C = λ (wavelength) * ƒ (frequency)
wavelength the distance between two consecutive peaks or troughs of a wave. see picture if needed
Frequency is the number of waves that pass a given point in one second. see picture if needed.
Electromagnetic Spectrum all of the frequencies or wavelengths of electromagnetic radiation
Ground State lowest possible state of energy for electrons, natural state of electrons
Excited State electrons gains energy, must release that energy in the form of light to go back to Ground State
Aufbau Diagram diagram that shows the pattern of electron orbitals for atoms. Ex: 1s2 2s2 2p6 3s2 3p6 4s1
Law of definite proportions a compound contains the same elements in exactly the same propositions by weight or mass
atomic mass = protons + neutrons
Hydrogen • In a group by itself<br>• Reactive gas – forms an explosive mixture with oxygen<br>• Reacts violently with many other elements<br>• Usually placed at the top of Family 1A, even though it is NOT a metal, nor a good conductor of heat or electricity
Family I-A • Good conductors of electricity <br>• Soft enough to cut with knife <br>• Not found in nature in uncombined states [in compounds that must be broken down]<br>• Reacts violently with cold water, makes hydrogen gas and a solution of metal hydroxide
Family II-A • React with water to produce alkaline solutions <br>• Not found uncombined in nature <br>• Less chemically reactive than Family I-A = Alkali Metals <br>• Harder than Alkali Metals
Family VII-A = Halogens • Include non-metals and metalloid (semi-metal) <br>o Example: Si and Ar <br>• Gases, liquid, and solid<br>• Do not exist in nature in uncombined state<br>• Compounds are fairly abundant – combine with Family I-A or Family II-A to form salts
Family VIII-A = Noble Gases • AKA rare gases because they occur in the atmosphere in very small amounts <br>• Inert = rarely combine or react with other elements (8 valence electrons make them very stable)<br>• Tend to exist as separate atoms rather than in combination
Rare Earth Elements often radioactive and can be used in nuclear reactors to produce electricity<br> ex: U (Uranium) and Pu (Plutonium)
Bond radius half the distance from center to center of two like atoms that are bonded together
Dmitri Mendeleev 1869, made first USABLE periodic table. <br> used all known elements, physical & chemical properties & atomic mass. <br> credited as the father of the Periodic Table <br> left blank spots in periodic table for other scientists to fill them in.
John Newlands 1865 – arranged the known elements by properties and atomic mass
Henry Moseley 1914 – adds atomic numbers to the Periodic Table
Semiconductors right side of the periodic table, between darker colors and lighter colors
Metals have the following properties: • Good conductors heat & electricity• Metal luster (shiny)• Malleable (can be bent molded)• Ductile (can be drawn into wire)• high density• Low ionization energy & electronegativities• Solid at room temperature (except Mercury = liquid)
Metals have the following properties: (continued) Want to lose valence electrons & form ionic or metallic bond
Nonmetals have the following properties: • Do not conduct heat or electricity• Are not malleable or ductile• Dull and brittle. Dull = not shiny, brittle = shatters easily• Many are gasses at room temperature but can also be a solid or liquid. •
Nonmetals have the following properties:(continued) Have high ionization energies and electronegativities • Want to gain valence electrons• Will form an ionic or covalent bond. [will bond with themselves]• Are good insulators [keep out heat and electricity, very poor conductors]
Metalloids or Semi-metals have the following properties: • properties of both metals and nonmetals. Ex: Silicon is shiny but brittle.• Reactivity depends on properties of other elements in the reaction. Ex: Boron acts as a non-metal when bonding with Sodium, but acts as a metal when bonding with Fluorine.
Metalloids or Semi-metals have the following properties (continued) • Electronegativities and ionization energy is between metals and nonmetals. • Can make good semi-conductors.
Electronegativity the ability of an atom to attract electrons
Electron affinity energy change that occurs when a neutral atom (same number of protons and electrons) gains an electron
Electron shielding the outer most electrons are held less tightly to the nucleus because the inner electrons block the nucleus from having control over the outer electrons. Example: Li – 3 electrons, very little shieldingRb – 37 electrons, more shielding.
Electron Shield in Comparison story: If you have 2 children, it’s easier to keep track of them than if you have 15 children. Similarly if an atom has 2 electrons around it, it has an easier time keeping them than if it has 37 electrons and they’re more easily stolen.
Cation lost electrons and is positively charged (metal)
Anion gains electrons and is negatively charged (nonmetal)
Created by: dhh