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52 Cards in this Set

  • Front
  • Back
What is an atom?
The structural unit of matter
what are the parts of an atom?
Proton (+) Neutron (neutral) Electron (-)
What is an element?
a substance that cannot be broken down to a simpler substance by ordinary chemical means (QAZ)
how many naturally occurring elements are there?
92 (all the others are man-made)
What is the atomic number of an element?
the number of protons in the nucleus. each element has a specific atomic number.
what is an isotope?
atoms that have the same number of protons and a different number of neutrons and are usually radioactive
why are radioactive isotopes important?
-used in radioactive dating
-used in medicine as tracers and for PET scans
how do charged particles react?
opposites attract
where are the electrons found?
outside the nucleus in energy shells or levels. they occupy an area like a cloud
what is a molecule?
the smallest particle of a compound
what is a compound?
2 or more atoms that are chemically combined. they have definite proportions. new chemical properties. can be separated only by chemical means (co2, c6h12o6)
what is a mixture?
just opposite of a compound. not chemically combined. no definite proportions. no new properties. can be separated physically (salt water)
what determines stability or reactivity of atoms?
-number of electrons in its outermost shell

stable- outermost shell is full
reactive- outermost shell is partially full
how do chemical bonds form
by losing gaining or sharing electrons
what produces chemical reactions?
making or breaking of the chemical bonds
what are ions?
charged atoms. that is the number of electrons and protons are not equal.
what is ionic bonding?
result of the transfer of electrons. one atom gains electrons and the other loses electrons. (sodium)
what is covalent bonding?
sharing of electrons (water)
what type of bonding is found in most biological molecules?
what are the most common atoms found in biological molecules?
what is an example of a polar molecule and why?
water. electrons spend more time around the oxygen
what are free radicals?
molecules that have unpaired electrons
why are free radicals important to understand?
they destroy biological molecules and can result in cell death
what can produce free radicals?
radiation, exhaust chemicals, industrial chemicals
what can make free radicals harmless?
antioxidants (vitamin c and e)
what causes hydrogen bonding?
polar molecules have positive and negative areas so one molecule attracts another
where did life probably start?
the ocean
what percent of body weight is h2o?
what is water good at?
dissolving substances. it is a solvent.
what is a solute?
the substance being dissoved
what does hydrophilic mean?
what gases are dissolved in h2o?
o2, co2, n
what is the watery substance inside a cell?
what does hydrophobic mean?
water hater
what is cohesion?
attraction of like molecules
why are cohesion and surface tension important to living things?
-surface tension allows some organisms to move across water
-cohesion allows plants to pull water up from roots to leaves
what causes cohesion and surface tension?
hydrogen bonds
what is adhesion?
attraction of unlike molecules
what are acids?
substances that have a high concentration of hydrogen ions (H+) in solution
what are bases?
substances that have a high concentration of hydroxide ions (OH-) in solution.
what is the pH scale?
a system of measurement used to measure the hydrogen ion concentration
below 7=acid
above 7=base
what is the pH of cytoplasm and body fluids?
how does the body maintain its pH?
by substances called buffers. (bicarbonates & phosphates)
how does high temperature affect living things?
it damages enzymes making them ineffective
how does low temperature affect living things?
slows down enzyme action
how do subfreezing temps affect living things?
lethal to cells. ice crystals form and rupture cells.
what are 3 important properties of water?
high specific heat, high heat of vaporization, and high heat of fusion
what is specific heat?
amount of energy required to raise the temp of 1 g of water 1 degree C. therefore water heats up and cools down slowly.
what is heat of vaporization?
amount of heat required to convert liquid water into water vapor. requires 539 calories/gram. for this reason when sweat vaporizes it cools down the body.
what is heat of fusion?
amount of energy that must be removed before water freezes
what is unusual about frozen water?
expands, lower density value, and it floats
why is ice important to ponds and lakes?
ice insulates them so fish and plants are not killed during the winter due to the cold temps.