Mastering Biology: chapter 2

Which of the following trace elements needed by humans is commonly added to table salt? -magnesium -iodine -fluoride -iron

iodine

Silicon is an element that is found directly underneath carbon in the periodic table. How many electrons are in the valence shell of a silicon atom? -1 -4 -2 -6

4

The temperature of evaporation is much higher for water than for alcohol. Without knowing more about the chemistry of alcohol, which of the following is the most logical chemical explanation for this phenomenon? -Alcohol molecules are more cohesive than water molecules. This means that as alcohol molecules evaporate, they pull other alcohol molecules into the air along with them. -Alcohol has a higher surface tension than water. This means that alcohol molecules can easily break away from other alcohol molecules and evaporate at a lower temperature. -Ionic bonds form between alcohol molecules. These are the weakest type of bond and are easier to break than the hydrogen bonds between water molecules. -Fewer hydrogen bonds form between alcohol molecules. As a result, less heat is needed for alcohol molecules to break away from solution and enter the air.

Fewer hydrogen bonds form between alcohol molecules. As a result, less heat is needed for alcohol molecules to break away from solution and enter the air.

What is the fundamental difference between covalent and ionic bonding? -Covalent bonding involves only the outermost electron shell; ionic bonding also involves the next electron shell inside the outermost shell. -In covalent bonding, both partners end up with filled outer electron shells; in ionic bonding, one partner does and the other does not. -Covalent bonds form between atoms of the same element; ionic bonds form between atoms of different elements. -In a covalent bond, the partners share a pair of electrons; in an ionic bond, one partner accepts electrons from the other.

In a covalent bond, the partners share a pair of electrons; in an ionic bond, one partner accepts electrons from the other.

When water freezes, ice floats. Why? -The ice molecules are moving faster than liquid water molecules. -Ice is colder than liquid water. -Ice is denser than liquid water. -In ice, the water molecules are farther apart than in liquid water.

In ice, the water molecules are farther apart than in liquid water.

Sodium chloride (NaCl) dissolves in water because water molecules _____. -have a high specific heat -lose electrons -have a pH near 7 -are polar

are polar

Trace elements _____. -are very rare on Earth -are required in very small amounts -enhance health but are not essential for long-term survival -can be used as labels to trace atoms through an organism's metabolism

are required in very small amounts

What is an acid? An acid _____. -donates hydrogen ions to solutions -removes hydrogen ions from solutions -is a versatile solvent -contains hydrogen

donates hydrogen ions to solutions

The most widely effective solvent for organisms is a material that is _____. -volatile -nonpolar -ionic -polar

polar

The hydrogen atoms of a water molecule are bonded to the oxygen atom by ________ bonds, whereas neighboring water molecules are held together by ________ bonds. -hydrogen; polar covalent -ionic; covalent -polar covalent; hydrogen -polar covalent; ionic

polar covalent; hydrogen

Which of the following subatomic particles contributes toward the atomic mass of hydrogen? -proton -neutron -electron -element

proton

Two atoms of the same element must have the same number of _____. -neutrons plus protons -protons -electrons -neutrons

protons

Which of the following particles are found in the nucleus of an atom? -protons and electrons -only protons -protons and neutrons -only electrons

protons and neutrons

Table salt is formed when -a hydrogen bond forms between sodium and chlorine. -sodium donates its single outer electron to chlorine. -chlorine gives an electron to sodium. -sodium and chlorine share electrons to form a bond.

sodium donates its single outer electron to chlorine.

Which of the following substances is a compound? liquid nitrogen hydrogen gas sodium sugar

sugar

Grapefruit juice is approximately pH 3, and tomato juice is approximately pH 4. A glass of grapefruit juice contains _____ H+ as a glass of tomato juice. -half as much -ten times as much -one-tenth as much -twice as much

ten times as much

Which of the following is a trace element in the human body? -zinc -nitrogen -hydrogen -oxygen

zinc

What is the atomic mass of an atom that has 6 protons, 6 neutrons, and 6 electrons? -18 -6 -12 -8

12

The sodium atom contains 11 electrons, 11 protons, and 12 neutrons. What is the mass number of sodium? -22 -34 -23 -11

23

Chemical reactions do not create or destroy matter but simply rearrange it. Which example is the correct completed equation for this reaction? 4 NH3 + _____ O2 → _____ NO + _____ H2O -4 NH3 + 6 O2 → 4 NO + 5 H2O -4 NH3 + 5 O2 → 4 NO + 6 H2O -4 NH3 + 1 O2 → 2 NO + 5 H2O -4 NH3 + 5 O2 → 2 NO + 1 H2O

4 NH3 + 5 O2 → 4 NO + 6 H2O

A nutrition facts label from a fortified cereal states that in a single serving of cereal there is 8% of the percent daily value of the element phosphorous. The label also says that a single serving of cereal plus one-half cup of skim milk has 20% of the percent daily value of phosphorus. Which of the following statements is false? -Eating five servings of cereal and two and a half cups of skim milk will give you 100% of the phosphorus that you need for one day. -A half-cup of skim milk contains 12% of the percent daily value of phosphorus. -A half-cup of skim milk contains twice as much phosphorus as a serving of cereal. -The amount of phosphorus in six servings of cereal is equal to the amount of phosphorus in two cups of skim milk.

A half-cup of skim milk contains twice as much phosphorus as a serving of cereal.

How are cohesion and surface tension related to the chemical properties of water? -All have to do with ionic interactions. -All are produced by covalent bonding. -All are properties related to hydrogen bonding. -All are results of the structure of the hydrogen atom.

All are properties related to hydrogen bonding.

In plants, the process of photosynthesis produces glucose (C6H12O6) and oxygen from carbon dioxide and water. Which of the following statements about photosynthesis is true? -All of the carbon atoms from the carbon dioxide atoms are found in glucose. -More atoms are present at the beginning than at the end. -More carbon dioxide is released from the plant than is absorbed. -Water is synthesized by the plant from H2 and O2.

All of the carbon atoms from the carbon dioxide atoms are found in glucose.

Covalent bonds can occur where atoms share one or more pairs of electrons. Which of the following would form a double covalent bond? -Cl2 -CO2 -NH3 -NaCl

CO2

How are ionic bonds formed? -Ionic bonds are formed by the transfer of a hydrogen atom from one molecule to another. -Ionic bonds are formed only between isotopes. -In ionic bonds, one atom gives up an electron to a second atom. -Ionic bonds are formed when electrons are shared.

In ionic bonds, one atom gives up an electron to a second atom

Which of the following statements regarding the oxygen atom of a water molecule is true? -Oxygen is more positively charged than the hydrogen atoms. -Oxygen attracts electrons less strongly than the hydrogen atoms. -Oxygen is attracted to the negatively charged atoms of other molecules. -Oxygen is more electronegative than the hydrogen atoms.

Oxygen is more electronegative than the hydrogen atoms.

Which of the following statements regarding chemical reactions is false? -Although the atoms of a reaction's reactants and products are identical to each other, their molecular formulas differ. -Chemical reactions involve the making and breaking of chemical bonds. -Some chemical reactions create electrons; others destroy them. -The reactants contain the same number of atoms as the products.

Some chemical reactions create electrons; others destroy them.

Which of the following statements about radioactive isotopes is true? -The energy emitted by radioactive isotopes can break chemical bonds and cause molecular damage in cells. -When given a choice between radioactive and nonradioactive isotopes of the same atom, living cells are more likely to incorporate the radioactive isotopes into their structures. -Radioactive elements are natural and therefore not harmful. -The nuclei of radioactive isotopes are unusually stable, but the atoms tend to lose electrons.

The energy emitted by radioactive isotopes can break chemical bonds and cause molecular damage in cells.

The pH of human blood is maintained at around pH 7.4. Why does a buffer system need to be present in blood to protect against changes in pH due to increases in acids? -Adding bases doesn't alter the pH of most solutions significantly. -Under normal conditions, only acids need to be buffered. -The metabolic processes of the body produce more acids than bases. -Our blood is not exposed to any bases.

The metabolic processes of the body produce more acids than bases.

What happens to an atom if the electrons in the outer shell are altered? -The properties of the atom change. -The atom becomes radioactive. -The atom disintegrates. -The atom's characteristics change, and it becomes a different element.

The properties of the atom change.

The hydrogen bonds in liquid water are less stable than in ice. Why? -In liquid water, the molecules form delicate crystals. -There is less movement of molecules in colder conditions. -Ice is insulated by the liquid water below. -Ice is denser than liquid water.

There is less movement of molecules in colder conditions.

Which of the following describes a covalent bond? -Molecules linked by covalent bonds are less dense when in solid form than when in liquid form. -It involves an atom that gains an electron. -Two or more atoms share electron pairs. -A hydrogen atom with a partial positive charge is attracted to another atom with a partial negative charge.

Two or more atoms share electron pairs.

Which of the following statements regarding matter is false? -All matter exists in the form of compounds. -All life is composed of matter. -All matter is composed of elements. -All matter has mass.

all matter exists in the form of compounds

Radioactive isotopes -are frequently added to foods as nutritional supplements. -can be used in conjunction with PET scans to diagnose diseases. -do not occur naturally. -are never incorporated into organic compounds.

can be used in conjunction with PET scans to diagnose diseases.

The tendency of water molecules to stick together is referred to as -transpiration. -cohesion. -adhesion. -polarity.

cohesion

Which of the following bonds are arranged from strongest to weakest in a biological system? -hydrogen, ionic, covalent -ionic, covalent, hydrogen -hydrogen, covalent, ionic -covalent, ionic, hydrogen

covalent, ionic, hydrogen

An atom's reactivity is determined by its _____. -electron configuration -size; smaller things are more reactive -nucleus -protons

electron configuration

An atom and an ion of the same element differ in the number of _____. protons either protons or electrons neutrons electrons

electrons

A substance that cannot be broken down into other substances by ordinary chemical procedures is known as a(n) _____. -molecule -electron -compound -element

element

The number of protons in an uncharged atom _____. -equals the total number of electrons in the orbital shells -varies with the different isotopes -determines its mass number -equals the number of neutrons

equals the total number of electrons in the orbital shells

For most atoms, a stable configuration of electrons is attained when the atom __________. -achieves a zero net charge -has moved all its electrons to its outermost shell -has a completely filled outermost shell -has as many protons as neutrons

has a completely filled outermost shell

Typically, nitrogen atoms are composed of electrons, protons, and neutrons. An isotope of nitrogen could -have more neutrons than the usual nitrogen atom. -have more protons than the usual nitrogen atom. -be positively charged. -be negatively charged.

have more neutrons than the usual nitrogen atom

Water can resist temperature change because _____. -hydrogen bonding increases water's ability to vaporize -evaporation of water heats the surface it leaves -large bodies of water cannot store heat -heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur

heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur

You've been experiencing acid indigestion lately, and you'd like a quick fix for the problem. You do a little research on the Internet and discover that your problem is caused by excess stomach acid. In the pharmacy aisles, however, you're having a little trouble deciding what to purchase to address the problem. At the pharmacy counter, the clerk recommends that you purchase PEPCID AC or Alka-Seltzer tablets. If you could check the pH of the recommended tablets, you would expect it to be -lower than 7. -higher than 7. -exactly 7. -pH neutral.

higher than 7

Water's surface tension and heat storage capacity are accounted for by its -orbitals. -size. -mass. -hydrogen bonds.

hydrogen bonds

Because the molecules of water are farther apart in ice than in liquid water, _____. -ice is denser than liquid water -ice expands when it melts -ice vaporizes before liquid water does -ice floats

ice floats

Electrons move about the nucleus of an atom in the same way that -boats cross a lake. -birds migrate to a new winter home. -cars are parked along the sides of a street. -insects fly around a bright lamp at night.

insects fly around a bright lamp at night

Medicines are often administered in pill form. In many cases, the active ingredient of the pill (the drug) is joined to another substance by ________. This forms a(n) ________, which is stable in the dry environment of a pill bottle but dissociates under the wet conditions of the digestive system to release the drug to the body. -covalent bonds; salt -ionic bonds; acid -hydrogen bonds; base -ionic bonds; salt

ionic bonds; salt

Which four elements are the primary components of important biological molecules, such as proteins, fats, and carbohydrates? -nitrogen, carbon, hydrogen, and oxygen -oxygen, carbon, hydrogen, and water -calcium, nitrogen, carbon, and oxygen -sodium, hydrogen, carbon, and oxygen

nitrogen, carbon, hydrogen, and oxygen

A hydrogen atom has one electron. How many covalent bonds can hydrogen form? -one -four -none -two

one

A covalent bond is likely to be polar if _____. -the two atoms sharing electrons are equally electronegative -one of the atoms sharing electrons is much more electronegative -the two atoms sharing electrons are of the same element -it is between two atoms that are both very strong electron acceptors

one of the atoms sharing electrons is much more electronegative

In the equation 2 H2 + O2 → 2 H2O, -H2, O2, and H2O are all compounds. -only H2O is a compound. -only H2 and O2 are compounds. -H2, O2, and H2O are all elements.

only H2O is a compound.

In hydrochloric acid (HCl), chlorine has greater electronegativity than hydrogen. Therefore, _____. -the H side of an HCl molecule would have a slight negative charge -HCl is a nonpolar molecule -the H side of an HCl molecule would have a slight positive charge -H and Cl cannot interact chemically

the H side of an HCl molecule would have a slight positive charge

When you add acid to a solution, _____. -the hydrogen ion concentration increases and lowers the pH -the hydrogen ion concentration increases and raises the pH -the hydrogen ion concentration decreases and raises the pH -the hydrogen ion concentration decreases and lowers the pH

the hydrogen ion concentration increases and lowers the pH

Generally, what determines the number and kinds of chemical bonds an element can make and the chemical reactivity of an element? -mean energy level of its electrons -number of protons plus the number of neutrons -the number of electrons in its outer shell -number of electron shells present in the atoms

the number of electrons in its outer shell

Which of the following best describes the atomic number of an atom? -the number of neutrons in the atom -the number of protons in the atom -the number of electrons in the atom -the number of protons, electrons, and neutrons in the atom

the number of protons in the atom

Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal). -three fewer neutrons -three more neutrons -three fewer protons -three more protons

three fewer neutrons