an example of a stimulus that a plant would respond to is:
plants can respond only to certain stimuli in the environment, such as sunlight
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which of the following things would be considered complex and organized?
red blood cell in the human body
dna is a molecule that directly allows a living thing to:
the process of homeostasis is:
how organisms maintain a relatively constant internal environment. correct. homeostasis is the maintenance of a relatively constant internal environment even in changing external environments.”
living systems need energy to:
replace worn-out parts and build new parts.
help maintain a relatively constant internal environment.
the complexity of living systems:
is also highly organized.
identify a characteristic that is representative of some, but not all, life-forms.
movement over great distances
the innermost electron shell of an atom can hold up to _____ electrons.
2 this is the maximum number of electrons that can occupy the innermost electron shell.
which of these relationships is true of an uncharged atom?
the number of protons is equal to the number of electrons.
in this situation the number of positive charges is equal to the number of negative charges
what determines the types of chemical reactions that an atom participates in?
the number of electrons in the outermost electron shell
what is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
6 this is an atom of carbon, an element with 6 protons. atomic number is the number of protons in an atom
which of these refers to atoms with the same atomic number but different atomic masses?
these atoms are isotopes.
atoms with the same atomic number and different atomic masses are referred to as isotopes.
fluorine’s atomic number is 9 and its atomic mass is 19. how many neutrons does fluorine have?
10 atomic mass is equal to the number of protons plus the number of neutrons (19-9 = 10).
an uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. how many protons does boron have?
the atomic number is equal to the number of protons.
what type of bond is joining the two hydrogen atoms?
a covalent bond is one in which electron pairs are shared.
a(n) _____ refers to two or more atoms held together by covalent bonds.
a molecule is defined as two or more atoms held together by covalent bonds.
this atom can form up to _____ single covalent bond(s).
there are four electrons in the outermost electron shell.
a(n) _____ bond joins these two oxygen atoms.
the oxygen atoms are sharing two pairs of electrons
atoms with the same number of protons but with different electrical charges _____.
are different ions
ions are charged atoms.
in salt, what is the nature of the bond between sodium and chlorine?
sodium and chlorine ions are attracted to each other
an ionic bond involves _____.
an attraction between ions of opposite charge
each water molecule is joined to _____ other water molecules by ____ bonds.
four … hydrogen
as can be seen in the illustration on page 1 of the activity titled “the polarity of water” a water molecule is joined to four other water molecules by hydrogen bonds.
the unequal sharing of electrons within a water molecule makes the water molecule _____.
the electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
the tendency of an atom to pull electrons toward itself is referred to as its _____.
in this molecule, what type of bond is found between the oxygen and hydrogens?
while oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
hydrogen bonds are weaker than covalent bonds because they do not involve sharing of electrons, and they are weaker than ionic bonds because they involve the attraction of partial (not full) opposite charges.
why isn’t this insect drowning?
the high surface tension of water allows the insect to remain on the surface.
what name is given to the bond between water molecules?
a hydrogen atom with a net positive charge is attracted to an oxygen atom with a net negative charge
in a neutral solution the concentration of _____.
hydrogen ions is equal to the concentration of hydroxide ions
what are an atoms subatomic particles?
protons, neutrons and electrons
6 co2 + 6 h2oc6h12o6 + 6 o2 the equation shows a ______ that leads to the change in composition in matter
6 co2 + 6 h2oc6h12o6 + 6 o2
in the equation, co2 is the____
6 co2 + 6 h2oc6h12o6 + 6 o2
in the equation c6h12o6 is the ______
6 co2 + 6 h2oc6h12o6 + 6 o2
in o2 the type of bond that holds the oxygen together is _______
a non-polar covalent bond
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four elements combine to make about 96% of the mass of the human body. which of the following elements is one of the four?
carbon atoms serve as the backbone for all biological molecules. the four elements that make up over 96% of the mass of a human body are hydrogen, oxygen, nitrogen, and carbon
in an atom with a neutral overall charge, the number of protons is equal to the _________.
number of electrons
each electron has a negative charge and each proton has a positive charge. thus, in a neutral atom, the number of electrons is equal to the number of protons.
the simplest unit of matter that still retains the properties of an element is a(n) _____.
substances that contain two or more elements in a fixed ratio are called _____.
when elements combine in fixed ratios and are joined together by chemical bonds, they form compounds. on earth, compounds are much more common than elements.
carbon-12 and carbon-13 are different in the number of their _____.
carbon-12 and carbon-13 are isotopes. isotopes differ only in the number of their neutrons.
what is the term for atoms that are electrically charged as a result of gaining or losing electrons?
ion ions are atoms that are electrically charged as a result of gaining or losing electrons
which of these is a type of chemical bond that involves the sharing of electrons?
covalent covalent bonds involve sharing a pair of electrons.
what type of bond joins neighboring water molecules?
hydrogen bonds form weak attractions between neighboring water molecules.
the four most common elements found in living things are
carbon, oxygen, nitrogen, and hydrogen
an atom with a positive charge has ______.
more protons than electrons
an uncharged atom of gold has an atomic number of 79 and an atomic mass of 197. this atom has ______ protons, ______ neutrons, and ______ electrons.
how do radioactive isotopes differ from isotopes?
radioactive isotopes are unstable; isotopes are stable.
the second electron shell of an atom can hold a maximum of ______ electron(s).
nitrogen has an atomic number of 7; therefore, it has ______ electrons in its outermost electron shell.
the bond between oppositely charged ions is a(n) ______ bond.
what name is given to bonds that involve the sharing of electrons?
why is water considered a polar molecule?
the oxygen end of the molecule has a slight negative charge, and the hydrogen end has a slight positive charge.
adjacent water molecules are joined by ______ bonds.
relative to a ph of 6, a ph of 4 has a ______.
100 times higher h+ concentration