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Matter
Anything that occupies space and has mass
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Element
- Substance that can't be broken down further
- 92 natural elements, several synthetic elements
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Compound
2+ elements combined in a fixed ratio
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Trace elements
- There are 25 elements essential to life- oxygen, carbon, nitrogen a hydrogen make up 96.3% and 7 other elements make up 3.7%
- The other 14 elements are essential only in minute quantities
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Atom
Smallest unit of matter that still behaves like an element
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Proton
Subatomic particle with a positive charge
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Electron
Subatomic particle with a negative charge
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Neutron
Subatomic particle with no charge
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Nucleus
- An atom's central core
- Consists of protons and neutrons
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Atomic number
All atoms have a specific number of proteins unique to their element
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Mass number
Sum of the protons and neutrons
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Atomic mass
Very similar to mass number but has the weight of electrons too
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Isotopes
Atoms of the same element with different numbers of neutrons
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Radioactive isotope
- An atom's nucleus decays spontaneously
- Gives off particles and radiation
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Electron shells
Electrons move around an atom's nucleus at certain energy levels- the shells
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Chemical bonds
Attractions that hold atoms together
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Covalent bond
Bond where atoms share electrons
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Molecule
2+ atoms held together by covalent bonds
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Electronegativity
An atom's attraction for shared electrons
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Nonpolar covalent bonds
Electrons are shared equally between atoms
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Polar covalent bond
- Unequal sharing of electrons
- One atom partially positive one slightly negative
- Water
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Polar molecule
A molecule with unequal distribution of charges
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Ion
Atom/molecule with an electrical charge because they lost or gained an electron
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Ionic bond
2 ions with opposite charges attracted and held together
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Hydrogen bond
- Weak but very important
- Partial positive hydrogen atoms attract to nearby negative atoms
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Chemical reaction
- Breaking and making of chemical bonds
- Change the composition of matter
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Reactants
Starting material in chemical reactions
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Products
Material that results from chemical reactions
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Cohesion
- Molecules of the same kind stick together
- Stronger for water
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Adhesion
One substance clinging to another
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Heat
Amount of energy associated with the movement of atoms
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Temperature
Measures the intensity of heat
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Evaporative cooling
- When a substance evaporates, the surface is left cooler than before
- Greatest energy leaves so lower energy and lower temp remain behind
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Solution
Liquid with a uniform mixture of 2+ substances
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Solute
- Substance that is dissolved
- Usually a salt
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Aqueous solution
Water is the solvent of a solution
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Acid
Donates hydrogen atoms to solutions
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Base
Removes hydrogens from a solution
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pH scale
Describes how acidic or basic a solution is
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Buffers
Minimize changes in pH to sustain life
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Acid precipitation
Rain snow or fog with a pH lower than 5.2
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Ocean acidification
- Carbon dioxide dissolves in seawater and lowers pH
- Produces carbonic acid
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