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Chemistry CHS
for Yasmeen
| Question | Answer |
|---|---|
| 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) |
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dhh
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