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biology exploring life ch 4

STUDY
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matter
anything that occupies space and has mass
element
pure substances that cannot be broken down by chemical means
trace elements
elements critical to health that make up less than 0.01% of body mass
compound
a substance containing 2 or more elements that are chemically combined in a fixed rate
atom
smallest partical of an element
proton
a subatomic partical with a unit of positive charge
electron
a subatomic partical with a unit of negitive charge
neutron
a subatomic partical with no charge
nucleus
in an atom the center core that contains protons and electrons and most of the mass
atomic number
the number of protons in an element
isotope
a different form of an element that has a different number a neutrons but the same number of protons
radioactive isotope
an isotope where the nucleus decays over time giving off raditation. they are useful in medcine and research
ionic bond
a bond where an atom transfers electrons to other atoms in order to have a complete outer energy level
ions
atoms that have a charge as a result of gaining or losing electrons
chemical reactions
breaking of ols and formation of new chemical bonds, the result in new substances
reactants
the starting material for a reaction
products
the end result of a reaction
4 atoms that make up 96% of all living things
oxygen, carbon, hydrogen, and nitrogen
atomic mass
the number of protons and neutrons in an atom
polar molecules
a molecule in which opposite ends have opposite electric charges
hydrogen bonds
a bond created by the weak attraction of a slightly positive hydrogen atom to a slightly negative portion of another atom
cohesion
the tendency of molecules of the same kind to stick to one another
adhesion
the type af attraction that occurs between unlike molecules
solution
a uniform mixture of two or more substances
solvent
substances in a solution the disolves the other substance
solute
the substance that is dissolved
aqurous solution
where water is the solvent
acid
compound that has more H+ ions than other ions and that mesures less than 7 on the ph scale
base
a compound that has more OH- ions than other ions ans that mesures more than 7 on the ph scale
ph scale
describes how acidic or basic a solution is
water
a covalent molecule that is slightly polar and that has unique properties
temperature moderation
a property of water that allows water to heat up and cool down slower because the hydrogen bonds have to break or form
homogenous
same throughout
mixture
has two or more substances that can be seperated (a supension)
ph steps
each ph step (ie 7to 8) is a ten fold increase (so 8 is ten times more basic than 7)