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54 Cards in this Set
- Front
- Back
Matter
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Anything that occupies space and has mass
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What are the three physical states matter on Earth is found in?
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1. Solid
2. Liquid 3. Gas |
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Elements
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Substances that cannot be broken down into other substances
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What is matter composed of?
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Chemical elements
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How many naturally occurring elements are there on Earth?
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92 (plus several dozen made by humans)
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How many naturally elements are essential to life?
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25
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In order to most to least bountiful, what are the four naturally occurring elements that make up 96% of the human body?
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1. Oxygen 65%
2. Carbon 18.5% 3. Hydrogen 9.5% 4. Nitrogen 3.3% |
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Trace elements
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Elements essential for life, but only in very small amounts
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Compounds
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Substances that contain two or more elements in a fixed ratio. Most of the compounds in living organisms contain several different elements
i.e. NaCl, DNA |
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Ataom
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The smallest unit of matter that still retains the properties of an element. Composed of 3 subatomic particles
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What are the three subatomic particles that make up an atom?
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1. Proton
2. Electron 3. Neutron |
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Proton
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A subatomic particle with a single unit of positive electrical charge that stays tightly packed into the nucleus
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Neutron
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An electrically neutral particle that stays packed into the nucleus
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Electron
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A subatomic particle with a single unit of negative electrical charge. Move around the the nucleus in a spherical cloud
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What keeps electrons moving around the nucleus?
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The attraction between the negatively charged electrons and the positively charged protons
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What does it mean if an atom is "neutral"?
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When the atom has an equal number of protons and electrons and the net electrical charge is zero
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Atomic number
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Determined by the number of protons in an atom (this also determines which element it is)
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Mass number
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The sum of the number of protons and neutrons in an atoms nucleus
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Why are electrons not considered in the atoms atomic and mass numbers?
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Electrons has a tiny mass compared to the mass of protons and neutrons which are nearly identical
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Isotopes
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The different isotopes of an element have the same number of protons and electrons but different numbers of neutrons and therefore differ in mass
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Radioactive/unstable isotope
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One in which the nucleus decays, giving off particles and energy
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Which subatomic particles primarily determine how an atom behaves when it encounters other atoms?
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Electrons
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What determines how much energy an electron has?
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How far away it is from the nucleus (the farther away the greater the energy)
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What determines how many electron shells an atom has? How many electrons can each electron hold?
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The number of electrons the atom has. The innermost sell holds 2 electrons while the second and third shells each hold 8 electrons
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The fullness of which electron shell determines the chemical properties of an atom?
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The outermost shells- atom's whose outer shells are full tend not to participate in chemical reactions with other atoms
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Chemical bonds
What are the three types of chemical bonds? |
An attraction between atoms resulting from a sharing of outer-shell electrons or the presence of opposite charges of the atoms. the bonded atoms gain complete outer electron shells
1. Ionic 2. Covalent 3. Hydrogen |
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Ions
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Atoms tat are electrically charged as a result of gaining or losing electrons
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Ionic bonds
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The attraction between oppositely charged ions (transfer)
i.e. table salt (Na+ and Cl-) |
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Covalent bonds
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Forms when two atoms share one or more pairs of outer-shell electrons (share)
i.e. O2 |
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Molecule
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Atoms held together by covalent bonds
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What determines the number of covalent bonds can form?
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The number of covalent bonds an atom can form is equal to the number of additional electrons needed to fill its outer shell
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Double covalent bond
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When two molecules share two pairs of electrons
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Polar molecule
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Has opposite charges on opposite ends
i.e. oxygen end has a slight negative charge while the region around the two hydrogen atoms is slightly positive |
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Hydrogen bonds
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The weak electrical attractions between hydrogen atoms on one molecule (-) and an oxygen atom on the other molecule (+)
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Chemical reaction
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Changes in the chemical composition of matter, usually involves the breaking and forming of chemical bonds
*Cannot create or destroy matter, but only rearrange it |
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Reactants
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The starting materials in a chemical reaction
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Products
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The ending materials in a chemical reaction
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What are the four life-supporting properties water possesses?
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1. Its cohesive nature
2. Its ability to moderate temperature 3. The significance of ice floating 4. Its versatility as a solvent |
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Cohesion
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The tendency of molecules of the same kind to stick together
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The cohesion of water
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The cohesion of water is much stronger for water than other liquids. Related to water's high surface tension (how difficult it is to stretch or break the surface of a liquid)
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How water moderates temperature
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Because of hydrogen bonding, water has a stronger resistance to temperate change than most other substances. It can release a relatively large of amount to the surrounds while its temperature drops only slightly.
This moderates temperatures on earth |
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What is the difference between temperature and heat?
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Heat is the amount of energy associated with the movement of atoms and molecules in a body of matter
Temperature measures the average speed of molecules Heat is needed to break hydrogen bonds and therefore increase their speed and therefore temperature |
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Evaporative cooling
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When a substance evaporates the surface of the liquid remaining behind cools down (the molecules with the greatest energy tend to evaporate first)
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The biological significance of ice floating
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Ice floats because it is less dense than the liquid water around it, a consequence of hydrogen bonding
This floating ice insulates the liquid water below it, allowing life under it to persist |
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Solution
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A liquid consisting of a homogenous mixture of two or more substances
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Solvent
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The dissolving agent, the medium for chemical reactions
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Solute
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The substance that is dissolved
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Aqueous solution
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A solution in which water is the solvent
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Water as the solvent of life
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Water can dissolve an enormous variety of solutes necessary for life as they are polar
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Acid
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A chemical compound that releases H+ into a solution
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Base
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A compound that accepts H+ and removes it from the solution
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pH scale
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A measure of the H+ concentration in a solution on a scale of 0 (most acidic) to 14 (most basic)
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Where is pure water on the pH scale?
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At 7 as it is neutral and has an equal concentration of H+ and OH-
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Buffers
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Substances that prevent harmful changes in pH by accepting H+ when it is in excess and donating H+ when it is depleted
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