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52 Cards in this Set
- Front
- Back
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What is an atom?
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The structural unit of matter
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what are the parts of an atom?
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Proton (+) Neutron (neutral) Electron (-)
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What is an element?
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a substance that cannot be broken down to a simpler substance by ordinary chemical means (QAZ)
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how many naturally occurring elements are there?
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92 (all the others are man-made)
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What is the atomic number of an element?
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the number of protons in the nucleus. each element has a specific atomic number.
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what is an isotope?
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atoms that have the same number of protons and a different number of neutrons and are usually radioactive
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why are radioactive isotopes important?
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-used in radioactive dating
-used in medicine as tracers and for PET scans |
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how do charged particles react?
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opposites attract
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where are the electrons found?
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outside the nucleus in energy shells or levels. they occupy an area like a cloud
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what is a molecule?
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the smallest particle of a compound
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what is a compound?
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2 or more atoms that are chemically combined. they have definite proportions. new chemical properties. can be separated only by chemical means (co2, c6h12o6)
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what is a mixture?
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just opposite of a compound. not chemically combined. no definite proportions. no new properties. can be separated physically (salt water)
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what determines stability or reactivity of atoms?
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-number of electrons in its outermost shell
stable- outermost shell is full reactive- outermost shell is partially full |
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how do chemical bonds form
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by losing gaining or sharing electrons
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what produces chemical reactions?
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making or breaking of the chemical bonds
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what are ions?
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charged atoms. that is the number of electrons and protons are not equal.
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what is ionic bonding?
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result of the transfer of electrons. one atom gains electrons and the other loses electrons. (sodium)
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what is covalent bonding?
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sharing of electrons (water)
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what type of bonding is found in most biological molecules?
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covalent
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what are the most common atoms found in biological molecules?
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H C O N P S
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what is an example of a polar molecule and why?
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water. electrons spend more time around the oxygen
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what are free radicals?
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molecules that have unpaired electrons
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why are free radicals important to understand?
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they destroy biological molecules and can result in cell death
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what can produce free radicals?
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radiation, exhaust chemicals, industrial chemicals
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what can make free radicals harmless?
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antioxidants (vitamin c and e)
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what causes hydrogen bonding?
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polar molecules have positive and negative areas so one molecule attracts another
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where did life probably start?
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the ocean
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what percent of body weight is h2o?
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60%
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what is water good at?
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dissolving substances. it is a solvent.
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what is a solute?
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the substance being dissoved
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what does hydrophilic mean?
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waterloving
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what gases are dissolved in h2o?
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o2, co2, n
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what is the watery substance inside a cell?
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cytoplasm
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what does hydrophobic mean?
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water hater
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what is cohesion?
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attraction of like molecules
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why are cohesion and surface tension important to living things?
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-surface tension allows some organisms to move across water
-cohesion allows plants to pull water up from roots to leaves |
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what causes cohesion and surface tension?
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hydrogen bonds
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what is adhesion?
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attraction of unlike molecules
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what are acids?
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substances that have a high concentration of hydrogen ions (H+) in solution
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what are bases?
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substances that have a high concentration of hydroxide ions (OH-) in solution.
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what is the pH scale?
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a system of measurement used to measure the hydrogen ion concentration
below 7=acid 7=neutral above 7=base |
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what is the pH of cytoplasm and body fluids?
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7.4
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how does the body maintain its pH?
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by substances called buffers. (bicarbonates & phosphates)
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how does high temperature affect living things?
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it damages enzymes making them ineffective
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how does low temperature affect living things?
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slows down enzyme action
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how do subfreezing temps affect living things?
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lethal to cells. ice crystals form and rupture cells.
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what are 3 important properties of water?
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high specific heat, high heat of vaporization, and high heat of fusion
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what is specific heat?
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amount of energy required to raise the temp of 1 g of water 1 degree C. therefore water heats up and cools down slowly.
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what is heat of vaporization?
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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.
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what is heat of fusion?
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amount of energy that must be removed before water freezes
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what is unusual about frozen water?
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expands, lower density value, and it floats
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why is ice important to ponds and lakes?
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ice insulates them so fish and plants are not killed during the winter due to the cold temps.
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