No amino acid molecule by itself can speed up or catalyze reactions between other molecules; however, when amino acids are joined together to make a protein with catalytic properties, the new structure (enzymatic protein) can speed up the rate of a specific chemical reaction. What does this illustrate?
answer
emergent properties
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Which of the following statements is true about chemical nutrients in an ecosystem?
answer
They recycle within the ecosystem, being constantly reused.
question
Which of the following attributes is common to both prokaryotic cells and eukaryotic cells?
answer
The use of DNA as the information storage molecule
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How does DNA (deoxyribonucleic acid) encode information?
answer
In the sequence of nucleotides
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In order for a hypothesis to be able to be used in science, which of the following must be true?
answer
It is testable and falsifiable.
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Which of the following is true of a scientific theory
answer
It generates testable hypotheses, is supported by a large body of evidence, and is broad in scope.
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Which of the following is an example of qualitative data?
answer
The fish swam in a zigzag motion.
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Select the most accurate statement about the interaction between a tree and its physical environment.
answer
A tree and its physical environment alter each other.
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Select the correct statement about the process of scientific inquiry.
answer
It is possible to test hypotheses, such as those involving historical events, without conducting experiments.
question
A substance that cannot be broken down into other substances by ordinary chemical procedures is a(n) _____.
answer
Element
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Which of the following is a trace element required by most living organisms?
answer
Magnesium
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What is the mass number of an ion with 105 electrons, 158 neutrons, and a +1 charge?
answer
264
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Which of the following subatomic particles always has a positive charge?
answer
Proton
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Changing the number of _____ would change an atom into an atom of a different element.
answer
Protons in an atom
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The atoms of different phosphorus isotopes _____.
answer
have different numbers of neutrons
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The type of bonding and the numbers of covalent bonds an atom can form with other atoms is determined by _____.
answer
the number of unpaired electrons in the valence shell
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A carbon atom and a hydrogen atom form what type of bond in a molecule?
answer
Nonpolar covalent bond
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An ionic bond is formed when _____.
answer
one atom transfers an electron to another atom
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Hydrogen bonding is most often seen _____.
answer
when hydrogen is covalently bonded to an electronegative atom
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Chemical equilibrium is reached when _____.
answer
the forward and reverse reactions occur at the same rate so that the concentrations of reactants and products remain the same
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Which of the following statements correctly describes any chemical reaction that has reached equilibrium?
answer
The rates of the forward and reverse reactions are equal
question
Compared with 31P, the radioactive isotope 32P has
answer
one more neutron.
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The reactivity of an atom arises from
answer
the existence of unpaired electrons in the valence shell.
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What does the term electron orbital describe?
answer
An electron orbital describes a three-dimensional space where an electron can be found 90% of the time.
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What happens when two atoms form a chemical bond?
answer
A chemical bond forms when two atoms transfer or share outer electrons to complete their outer shells.
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Which of the following bonds can form between atoms of equal electronegativity?
answer
Van der Waals interactions can form between atoms of equal electronegativity.
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The innermost electron shell of an atom can hold up to _____ electrons.
answer
2
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Which of these relationships is true of an uncharged atom?
answer
The number of protons is equal to the number of electrons.
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What determines the types of chemical reactions that an atom participates in?
answer
the number of electrons in the outermost electron shell
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What is the atomic number of an atom that has 6 protons, 6 neutrons, and 6 electrons?
answer
6
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Which of these refers to atoms with the same atomic number but different atomic masses?
answer
These atoms are isotopes.
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Fluorine's atomic number is 9 and its atomic mass is 19. How many neutrons does fluorine have?
answer
10
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An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many protons does boron have?
answer
5
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A(n) _____ refers to two or more atoms held together by covalent bonds.
answer
Molecule
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What name is given to the bond between water molecules?
answer
Hydrogen
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Atoms with the same number of protons but with different electrical charges _____.
answer
are different ions
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In salt, what is the nature of the bond between sodium and chlorine?
answer
ionic
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An ionic bond involves _____.
answer
an attraction between ions of opposite charge
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Each water molecule is joined to _____ other water molecules by ____ bonds.
answer
Four...hydrogen
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The unequal sharing of electrons within a water molecule makes the water molecule _____.
answer
Polar
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The tendency of an atom to pull electrons toward itself is referred to as its _____.
answer
Electronegativity
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Why isn't this insect drowning?
answer
Surface Tension
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Water molecules have a polarity, which allows them to be electrically attracted to other water molecules and other polar molecules by weak chemical bonds known as _____.
answer
Hydrogen Bonds
question
Classify each statement as an example of adhesion, cohesion, or surface tension.
answer
An example of adhesion is the hydrogen bonding between water and another type of molecule, such as the molecules composing the side of a water glass or beaker.
Cohesion, on the other hand, is the attraction between like molecules. Water forms drops on a table because the water molecules are more strongly attracted to each other through hydrogen bonding than they are to the molecules composing the table's surface. Both adhesion and cohesion enable plants to transport water from the roots to the leaves against the force of gravity.
Surface tension is the resistance of the surface of a liquid to stretching or breaking. Water's surface tension results from the hydrogen bonds formed between the water molecules at the surface and between those surface molecules and the ones below. Water's high surface tension is evident when certain insects are able to walk on the water's surface.
question
The table shown here lists the specific heat of several substances.
Substance Specific heat
J/g/∘C
water 4.18
ethyl alcohol 2.44
benzene 1.80
sulfuric acid 1.40
Based on the information in the table, which of the following statements are true?
answer
Sulfuric acid is less resistant to temperature change than water.
Benzene is more resistant to temperature change than sulfuric acid.
More heat is required to raise the temperature of 1 g of water 1 ∘C than to raise the temperature of 1 g of ethyl alcohol 1 ∘C.
Water has a high specific heat due to the hydrogen bonding between water molecules.
question
Because organisms are made primarily of water, they resist rapid temperature changes. This useful quality is based on water's _____.
answer
High specific heat
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The amount of energy that must be absorbed or lost to raise or lower the temperature of 1 g of liquid water by 1°C _____.
answer
1 calorie
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Many of water's emergent properties, such as its cohesion, its high specific heat, and its high heat of vaporization, result from the fact that water molecules _____.
answer
are attracted to each other by partial negative and positive charges on the oxygen and hydrogen atoms, respectively
question
Sodas typically contain sugar, flavorings, coloring agents, and carbon dioxide dissolved in water. The best term to describe this mixture would be _____.
answer
an aqueous solution
question
If the molecular mass of a carbon atom is 12, the mass of a hydrogen atom is 1, and the mass of an oxygen atom is 16 daltons, how many molecules does one mole of table sugar (sucrose; C12H22O11) contain?
answer
6.02 x 10 to the 23rd
question
What is the pH of an aqueous solution with the hydronium ion concentration
[H3O+] = 2 x 10-14 M ?
answer
13.7
question
What is the molar concentration of [H3O+] in a cola that has a pH of 3.120?
answer
7.59 × 10−4
question
In a neutral solution the concentration of _____.
answer
hydrogen ions is equal to the concentration of hydroxide ions
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Which of these is the correct equation for the dissociation of water?
answer
H2O + H2O <==> H3O+ + OH-
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What is the charge on a hydronium ion?
answer
1+
question
What is the charge on a hydroxide ion?
answer
1-
question
About _____ molecules in a glass of water are dissociated.
answer
1 in 500,000,000
question
An acid is a substance that _____.
answer
increases the hydrogen ion concentration of an aqueous solution
question
A pH of 6 is how many times more acidic than a pH of 9?
answer
1000
question
Most acid precipitation results from the combination of _____ with water in the atmosphere, forming strong acids that fall with rain or snow.
answer
sulfur oxides and nitrogen oxides
question
Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?
answer
the absorption of heat by the breaking of hydrogen bonds
question
The bonds that are broken when water vaporizes are
answer
hydrogen bonds between water molecules.
question
Which of the following is a hydrophobic material?
answer
wax
question
We can be sure that a mole of table sugar and a mole of vitamin C are equal in their
answer
number of molecules
question
Which property of water allows dogs to cool themselves by panting?
answer
water's high heat of vaporization
question
Which property of water allows a paper towel to pick up a puddle of water?
answer
adhesion of water molecules to other kinds of molecules
question
Which property of water allows a water strider to walk on water?
answer
water's high surface tension
question
Identify all correct statements about the ionization of water.
answer
Dissociation of water is reversible.
Water ionizes to form hydroxide and hydronium ions.
Dissociation of water produces equal numbers of OH- and H+.
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