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what are all substances made out of?
elements
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Define: element
a substance that can't be broken down into simpler substances
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On earth, how many elements occur naturally?
90
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how many elements are essentail to living organisms?
25
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what four elements make up more than 96% of the mass of a human?
carbon, hydrogen, oxygen, and nitrogen
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Each element is abbreviated by a one or two letter ________.
symbol
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Define: atom
the smallest particle of an element that has the characteristics of that element
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what is at the center of an atom?
nucleus
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what is the nucleus made up of?
charged particles called protons and paricles called neutons, which have to charge
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All Nuclei are _______ charged because of the presence of ______.
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what forms a cloud around the necleus?
Are they positive or negative?
- electrons energy levels
- negative
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Define: energy levels
where electrons travel around necleua in certain regions
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What is the formula that is used to figure out how many electrons an energy level can hold?
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Atoms contain __________ numbers of electrons and protons. Therefore, they have____ ________.
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Define: isotopes
atoms of the same element that have different numbers of neutrons in the nucleus
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Define: compound
a substance that tis composed of atoms of different elements chemically combined.
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Why to atoms combine with other atoms?
to become be stable
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How to atoms become more stable by combining?
by sharing electrons
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Define: covalent bond
when two atoms share electons, covalent bond is the force that holds them together
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define: molecule
a group of atoms held together by covalent bonds and having no overall chrage.
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What two types of thing are bonding in a covalent bond?
a nonmetal to a nonmetal
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Define: ion
an atom that gains or loses electrons that has an electrical charge
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Define: ionic bond
a bond formed by the mutual attraction of two ions of opposite charge.
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What two types of thing are bonding in an ionic bond?
a metal to a nonmetal
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Ionic bonds do not form _____ _______.
true molecule
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Define: mixture
a combination of substance that don't combine chemically but retain ther individual properties
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Define: solution
a mixture in which one or more substances are distributed evenly in another substance
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water make up ___ to ____ percent of most organisms.
70 to 95
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Define: polar molecule
a molecule with an uneaqual sidtribution of charge
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water is _____.
a polar molecule
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Define: metabolism
total of all chemical reactions that occur within a living organism
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Define: reactants
substances that under-go chemical reactions
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Define: products
substances formed by chemical reactions
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What is the easiest way to understand chemical reacctions?
atoms are never created or destroyed, they are simply rearranged.
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Chemical equations must always be written so that they are _______.
Balanced
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What are the five unique properties of water?
- Universial solvent
- High Heat Capicity
- High Boiling and High Freezing Points
- high surface tenison
- expands when frozen
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Define: pH
a symbol to describe how acidic or basic a solution is; the pH scale ranges from 0 to 14; a solution with a pH of 7 is neutral, above 7 is basic, and below is acidic
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Define: Base
a substance that forms hydroxide ions in water; solutions with a pH of 7 or above
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Define: Acid
any substance that forms hydrogen ions in water; acidic solutions have pH below 7
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What is a family on the periodic table?
vertical rows
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What is a Period on the periodic table?
horizontal rows
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I'm a ______ based life form
carbon
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Why is Carbon the best?
- It has four open bonding sites
- non-metal
- carbon filter the best because it is so tightly bonded
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