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Sience
Unit 2 Study Guide
| Question | Answer |
|---|---|
| Democritus | believed that the universe was made of empty space and tiny bits of stuff. He called these tiny bits of stuff “atoms.” |
| Antoine Lavoisier | came up with the law of conservation of matter |
| volume | measured in cubic meters |
| matter | measured in grams |
| Density | mass/volume |
| model | a representation of an object, event, or idea |
| Physical models | can be seen or touched (Ex.: a globe) |
| Computer models | can be seen on a computer screen (Ex.: moving weather patterns on a computer) |
| Idea Models | concepts that describe how someone thinks about something in the natural world (Ex: Einstein’s E=mc2) |
| John Dalton | All elements are composed of atoms. Atoms are indivisible and indestructible particles |
| John Dalton | Atoms of the same element are exactly alike |
| John Dalton | Atoms of different elements are different |
| John Dalton | Compounds are formed by the joining of atoms of two or more elements |
| J.J. Thomson | discovered negatively charged electrons using a cathode ray tube. |
| J.J. Thomson | placed a magnet around the tube causing the light beam to bend |
| Ernest Rutherford | conducted his gold foil experiment. |
| Ernest Rutherford | discovered the positively-charged center of the atom |
| Ernest Rutherford | determined that atoms were mostly empty space. |
| James Chadwick | One of Ernest Rutherford's students |
| James Chadwick | discovered neutrons in the nucleus of the atom |
| Niels Bohr | proposed that electrons were located in specific energy levels and that electrons traveled in definite orbits around the nucleus. |
| Electron Cloud Model | current model of the atom |
| Electron Cloud Model | The darker the cloud (closer to the nucleus), the higher the probability that the electrons will be there |
| Dmitri Mendeleev | made the first periodic table |
| Dmitri Mendeleev | arranged the table by the atomic mass |
| How is today's periodic table arranged? | by the atomic number |
| horizontal rows | periods |
| How do you figure out what horizontal row an element is on? | by the amount of dots on the outer period |
| vertical columns | groups, or families |
| How do you figure out what column an element is on? | the amount of electrons |
| How many rows are there? | 7 |
| How many column are there? | 18 |
| Metalloids | “stair step” line between the metals and nonmetals |
| Metalloids | solids at room temperature |
| Nonmetals | brittle |
| Brittle | cannot change shape without breaking |
| Malleable | can be bent and pounded into various shapes, or flattened into thin sheets (foil) |
| Ductile | can be drawn into wire without breaking |
| Proton | positively charged particle located in the nucleus of the atom |
| Neutron | neutral charge located in the nucleus of the atom |
| Electron | negatively charged particle located outside the nucleus of the atom |
| Nucleus | the dense central portion of the atom |
| Proton | Its relative atomic mass is 1 atomic mass unit (amu). |
| Neutron | Its relative atomic mass is 1 amu |
| Electron | Its relative atomic mass is 1/1836 amu. |
| Atomic Number | the number of protons in the nucleus of an atom |
| Isotopes | elements with the same number of protons but different numbers of neutrons |
| The number of electrons are the same number as the? | atomic number |
| Mass Number | the sum of the protons and neutrons in the nucleus of an atom. This number is not listed on the periodic table |
| Average Atomic Mass | weighted average mass of all isotopes of an element |
| Solid | any substance with definite shape and volume. |
| Liquid | any substance with definite volume but no definite shape. |
| Gas | any substance with no definite shape or volume |
| Melting | going from a solid to a liquid. Must have an increase in energy. They absorb energy. This is an endothermic process. |
| Boiling | going from a liquid to a gas below the liquid’s surface. Must have an increase in energy. This is an endothermic process. |
| Evaporation | going from a liquid to a gas at the liquid’s surface. Still must have an increase in energy and is endothermic |
| Sublimation | going from a solid to a gas. Requires an increase in energy and is endothermic |
| Condensation | going from a gas to a liquid. Requires a decrease in energy, energy is released and is exothermic. |
| Thermal Energy | the total amount of kinetic and potential energy of an object. |
| Heat | the movement of thermal energy from hot to cold. Heat always moves from hot to cold |
| Temperature | the average kinetic energy of all the particles in an object. |
| Physical Property | a characteristic of a pure substance that can be observed without changing its identity. |
| Chemical Property | a characteristic of a pure substance that describes its ability to change into another substance – change its identity |
| Physical Change | a change that results in a change in appearance or form but not identity |
| Chemical Change | a change that results in a change in the identity of a substance |
| Endothermic | energy is absorbed, feels colder to touch (“Endo” = “in to”) |
| Exothermic | energy is released, feels hotter to touch. (“Exo” = “out of”) |
| Law of Conservation of Mass | Matter cannot be created or destroyed; but only transferred or transformed. |
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