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70 Cards in this Set
- Front
- Back
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matter
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anything that occupies space and has mass
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the various forms of matter are composed of one or more __________
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chemical elements
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element
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a pure substance that cannot be broken down into other substances by chemical means
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about _ elements are essential to life
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25
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what four elements make up about 96% or the living matter in your body
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oxygen
carbon hydrogen nitrogen |
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Trace elements
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elements that make up less than 0.01 percent of your body ass and are critical to your health
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compound
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a substance containing two or more elements that are chemically combined in a fixed ratio
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each element consists of a single kind of_____ that is different from the ______s of other elements
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atom
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atom
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the smallest possible particle of an element
"a piece" |
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subatomic particles
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even smaller components of what atoms of all elements are made up of
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proton
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a subatomic particle with a single unit of positive electrical charge (+)
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electron
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a subatomic particle with a single unit of negative electrical charge (-)
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neutron
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a subatomic particle that is electrically neutral
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electrically neutral
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no electrical charge
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an element's physical and chemical properties depend on
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the number and arrangement of its subatomic particles
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nucleus
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the central core of an atom. formed by the protons and neutrons packed together
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how do electrons mass compare with the mass of protons and neutrons? and how does this affect them?
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much less mass
causes them to continually move about the nucleus at great speed |
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what keeps the electrons close to the nucleus
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the attraction between the negatively charged electrons and the positively charged protons
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what is an important difference among elements
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the number of protons in their atoms
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all atoms of a particular element have the same amount of protons. the number of protons is...
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atomic number
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left alone, an atom tends to hod as many _____ as _____
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electrons as protons
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when an atom has as many protons as neutrons the atom is...
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electrically neutral
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are the number of protons constant
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yes
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are the number of electrons constant
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no, certain atoms can lose one or more electrons, while some atoms can gain one or two electrons
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isotopes
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alternate forms of some elements, have the same number of protons in their atoms but different number of neutrons
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radioactive isotopes
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an unstable isotope which the nucleus decays (breaks down) over time, giving off radiation in the form of matter and energy
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how are radioactive isotopes useful to medical research?
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living cells use radioactive isotopes just as they would use the nonradioactive forms
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how does an atom's structure determine how it reacts with other atoms?
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the key is the atom's electrons. electrons differ in the amount of energy they have and how tightly they are held by the protons in the nucleus. based on these properties chemists describe an atom's electrons as belonging to certain energy levels usually it is the electrons in the highest energy level of an atom that determine how the atom reacts
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the lowest energy level is located where?
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closest to the nucleus
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the first energy level is the _________ (lowest/highest etc...)
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lowest
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chemically reactive
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they tend to react with other atoms
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ionic bond
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type of chemical bond that occurs when an atom transfers an electron to another.
the attraction holding the oppositely charged ions together is the IONIC BOND |
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ions
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what the two atoms are referred to after the transfer of electrons in an ionic bond
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covalent bond
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a type of chemical bond that occurs when two atoms SHARE electrons.
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molecule
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formed by two or more atoms held together by a covalent bond
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structural formula
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indicates how atoms in a molecule are linked by bonds. each line between symbols represents a single covalent bond
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chemical formula
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tells you the number and types of atoms in a molecule
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space-filling model
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a drawing that depicts a three-deminsional model of a molecule.
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chemical reactions
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when molecules become rearranged into other molecules as existing chemical bonds break and new ones form. this results in the formation of one or more new substances.
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what happens when chemical bonds break
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absorbs energy from the surroundings
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what happens when new chemical bonds are formed
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realeses energy into the surroundings
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chemical equation
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a convenient way to describe a chemical equation
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reactants
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the starting materials in a reaction
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products
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the ending materials in a reaction
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what is unusual about the properties of water?
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the electrons of each covalent bond are not shred equally between oxygen and hydrogen atoms. oxygen pulls electrons much more strongly than does hydrogen. this unequal pull results in the shared electrons spending more of their time in the "neighborhood" of the oxygen atom
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why does oxygen have a much stronger pull than hydrogen?
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part of the reason is the oxygen nucleus has 8 protons and therefore has a stronger positive charge than the hydrogen nucleus which has one proton
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the result of unequal sharing of electrons in water is...
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causes the oxygen end of the molecule to have a slight negative charge, while the end with the two hydrogen atoms is slightly positive
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polar molecule
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a molecule in which opposite ends have opposite charge
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does water consist of polar molecules?
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yes
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hydrogen bond
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type of chemical bond. type of weak attraction between the hydrogen atom of one molecule and a slightly negative atom within another molecule
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cohesion
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the tendency of molecules of the same kind to stick to one another
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cohesion is much stronger for_______ than other______
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water
liquids |
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adhesion
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type of attraction that occurs between unlike molecules
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how do the properties of water affect life?
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trees depend on cohesion and adhesion to help transport water from their roots to their leaves
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thermal energy
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the total amount of energy associated with the random movement of atoms and molecules in a sample of matter
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temperature
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a measure of the average energy of random motion of the particles in a substance
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what happens when two substances differ in temperature
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thermal energy in the form of heat is transferred from the warmer substance to the cooler one
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solution
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a uniform mixture of two or more substances
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solvent
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the substance that dissolves the other substance and is present in the greater amount
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solute
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the substance that is dissolved and present in a lesser amount
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aqueous solution
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the result of a solution when water is the solvent
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acid
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a compound that donates H+ to a solution
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base
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a compound that recieves H+ ions from an aqueous solution. some do this by adding OH- ions which then combine with the H+ ions and form water molecules
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H+
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positively charged hydrogen atoms
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OH-
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hydroxide ions (a combo of an oxygen atom that carries a 1- charge)
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pH scale
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describes how acidic or basic a solution is. ranges from 0-14
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on the pH scale 0 is...(more acidic/more basic)
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ACIDIC
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on the pH scale 14 is...(more acidic/more basic)
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BASIC
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on the pH scale neutural is about...
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7/8
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buffers
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substances that cause a solution to resist changes in pH
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