 | Term | Definition |
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compound |
contains atoms of more than one type of element that are chemically bonded together; represented by chemical formulas such as NaCI (sodium chloride) or H20 (water); properties are different from the properties of elements that combine to form them *pg.40* |
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chemical property |
property that describes a change that occurs when one substance reacts with another (EX; Water changes to hydrogen and oxygen gases when electricity passes through it like in Thomas's experiment); property depends on what elements are in that substance and how they are arranged (EX: iron atoms with the mineral biotite will react with water and oxygen = rust; iron with chromium and nickel in stainless = no rusting) (pg. 40) |
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molecule |
group of atoms connected by covalent bonds *EX: two atoms of hydrogen sharing outer electrons with oxygen to form water* (pg 41) |
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mixture |
composed of two or more substances that are NOT chemically combined; (pg 43) |
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heterogeneous mixture |
components are not mixed evenly and each component retains its own properties; EX: 7 different rocks can combine to make one rock, but all 7 rocks still have the properties of the rock and still look like a rock (pg. 43) |
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homogeneous mixture |
components evenly mixed throughout; can't see the individual components; EX: Salt and Water combine to make salt water, but you can't see the salt and the water is no longer pure; also known as a solution (pg.43) |
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ions |
electrically charged atoms; more protons than electrons = positively charged; more electrons than protons = negatively charged (pg.41) |
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bond |
forces that hold the atoms in compounds together (pg. 40) |
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covalent bonds |
compound that forms by sharing outer electrons (pg. 41 look at figure 7) Here is a picture: http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt2/water.gif |
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ionic bonds |
compound that forms when atoms become positively or negatively charged; opposite charges attract (ex.positive attracted to negative, vice versa) the atoms only touch; (pg. 41) here is a picture: http://staff.jccc.net/PDECELL/chemistry/ionic.gif |
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metallic bonds |
electrons are free to move from one positively charged ion to another; the free movement of electrons is responsible for key characteristics of metals; movement of electrons allow electric currents to pass through |
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hydrogen bonds |
compound that forms without interactions of electrons; easily broken bond; Ex: A water molecule is made of a negative oxygen atom and two positive hydrogen atoms attached together. A negative oxygen atom in one molecule can be attracted to a positive hydrogen atom in DIFFERENT molecule, forming a bond. *pg.42; hard to explain look in book;here is a picture: http://www.lbl.gov/images/MicroWorlds/H2OH-bond.gif |
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