Bio Exam Ch 2
Which four elements make up approximately 96% of living matter? Oxygen, hydrogen, calcium, sodium Carbon, hydrogen, nitrogen, oxygen Carbon, sodium, chlorine, magnesium Carbon, phosphorus, hydrogen, sulfur Carbon, oxygen, calcium, sulfur
Carbon, hydrogen, nitrogen, oxygen
Which of the following represents a molecule characterized by polar covalent bonding? H2 H2O CH4 O2 NaCl
H2O
Which of the following properties of water enable(s) it to function as a regulator of temperature for living organisms? (Hint: Think about what happens when you are sunbathing.) High heat of vaporization High specific heat and high heat of vaporization Low specific heat High specific heat and low heat of vaporization High specific heat
High specific heat and low heat of vaporization
Which of the following best explains the attraction of water molecules to each other? Polar covalent bond Nonpolar covalent bond Hydrogen bond Ionic bond Electron-proton interaction
Hydrogen bond
What determines the cohesiveness of water molecules? Hydrogen bonds Ionic bonds Hydrophobic interactions Covalent bonds
Hydrogen bonds
What type of bond is easily disrupted in aqueous solutions (one in which the solvent is water)? Ionic Covalent Polar covalent
Ionic
Which of the following is the densest? Steam Ice Liquid water
Liquid water
What does H-O-H represent? Mixture including water Molecule of water Ionic bonding of water Atom of water
Molecule of water
How do buffers work? They accept and release OH-. They monitor the blood pH. They convert H+ and OH- to water. They soak up extra acid and base. They accept and release H+.
They accept and release OH-.
When water freezes, stable hydrogen bonds form between the water molecules that create an open, six-sided (hexagonal) arrangement. True False
True
A single covalent chemical bond represents the sharing of how many electrons? Four Two Six Three One
Two
If sulfur has an atomic number of 16, how many covalent bonds can it form with other atoms? Zero Two Four Six Eight
Two
Radioactive isotopes are biological tools that are often used to increase the pH of blood. measure the size of fossils. detect brain tumors and other important medical technologies. build up a store of calcium in a cell.
detect brain tumors and other important medical technologies.
The second electron shell is considered to be full when it contains ________ electrons.
eight
The part of the atom that has the greatest biological interest and interactions with other atoms is the electron. neutron. proton. innermost electron shell.
electron.
The chemical properties of an element are determined by the number of ________ in its outermost energy shell.
electrons
Polar covalent bonds form when an acid and a base are combined. ions are formed. more than one pair of electrons is shared. electrons are shared unequally between atoms. atoms from two molecules are repelling each other.
electrons are shared unequally between atoms.
Hydrophilic molecules do not readily dissolve in water. are repelled by water. are neutral and nonpolar. readily dissolve in water. form hydrogen bonds among themselves.
readily dissolve in water.
Carbon has atomic number 6. Carbon most likely loses protons. shares neutrons. loses electrons. shares protons. shares electrons.
shares electrons.
Free radicals are considered dangerous because they emit dangerous radiation. steal electrons from other atoms, causing those atoms to become unstable. damage oxygen and cause it to become an antioxidant. attack the atomic nucleus.
steal electrons from other atoms, causing those atoms to become unstable.
A basilisk lizard can run across the surface of a pond due to a property of water called ________.
surface tension
If you place a feather on the surface of a bowl of water, the feather remains suspended on the surface due to the surface tension of the water. density of the water. polarity of the water. fact that water is a good solvent.
surface tension of the water.
Your friend does a belly flop into a swimming pool. The stinging pain he feels is most likely due to the fact that water is a good solvent. surface tension of water (caused by the large number of hydrogen bonds that form between water molecules). hydrophobic nature of your friend's skin. pH of the water.
surface tension of water (caused by the large number of hydrogen bonds that form between water molecules).
Sweating is a useful cooling mechanism for humans because water takes up a great deal of heat in changing from its liquid state to its gaseous state. is an outstanding solvent. takes up a great deal of heat in changing from its solid state to its liquid state. can exist in two states at temperatures common on Earth. ionizes readily.
takes up a great deal of heat in changing from its liquid state to its gaseous state.
Which of the following results from a transfer of electron(s) between atoms (e.g., NaCl)? Electron-proton interaction Hydrogen bond Nonpolar covalent bond Ionic bond Polar covalent bond
Ionic bond
The formation of sodium chloride (NaCl) is the result of attraction between opposite charges. chemical unreactivity. covalent bonding. repelling between the same charges.
attraction between opposite charges.
The human body must maintain a constant pH. In the blood, bicarbonate serves as a(n) ________ to help maintain the necessary pH. buffer base acid solvent
buffer
Water moves through a plant because of the property of high specific heat. cohesion. high heat of fusion. high heat of vaporization.
cohesion
What property of water, in which water molecules stick to each other, is responsible for the ability of plants to get water from their roots up to their leaves?
cohesion
Sodium (Na), atomic number 11, has a tendency to lose an electron in the presence of chlorine. After losing the electron, Na has ________ protons in its nucleus. 10 11 12 21 22
11
Which of the following pairs has the most similar chemical properties to each other? 16O and 32S 12C and 28Si 1H and 22Na 12C and 14C 1H and 2He
12C and 14C
How does a base differ from an acid?
A base is a solution with a concentration of OH- that is higher than the concentration of H+ (pH greater than 7). An acid has a H+ concentration that exceeds its OH- concentration (pH less than 7).
Iron is an important element in human body cells. If iron has an atomic number of 26, what does this tell you about this element? An iron atom has 26 protons. An iron atom is unable to become an isotope. An iron atom has 13 electrons and 13 protons. An iron atom has 13 protons and 13 neutrons.
An iron atom has 26 protons.
Scientists recommend a diet rich in antioxidants to stay healthy. What occurs at the atomic level to explain this recommendation? Antioxidants steal electrons, which gives cells extra energy. Antioxidants cause an increase in pH, which is necessary for neutrality in cells. Antioxidants are inert and do not interact with free radicals. Antioxidants prevent free radicals from attacking other atoms or molecules.
Antioxidants prevent free radicals from attacking other atoms or molecules.
When the acidic level of human blood increases, how is the proper balance of hydrogen ions (H+) restored? H+ ion-donor levels increase. Bicarbonate (HCO3-) accepts H+ ions and forms carbonic acid. Carbonic acid eats up the extra OH- ions. Bicarbonate (HCO3-) releases H+ ions that combine with excess OH- ions to form H2O.
Bicarbonate (HCO3-) accepts H+ ions and forms carbonic acid.
Which of the following is attracted to the hydrogen "end" of a water molecule, as depicted in this figure? Na+ H NaCl Cl-
Cl-
What is the difference between covalent and ionic bonds?
Covalent bonds are the sharing of electrons between atoms, whereas ionic bonds are the electric charge attraction between two ions (typically a metal and a non-metal).
The attractive force that holds two or more water molecules together is an example of an ionic bond. True False
False
Water surface tension is a result of the cohesive nature of water molecules. True False
True
more stable than a hydrogen atom (atomic number 1)?
Two electrons completely fill the outermost electron shell of helium, but hydrogen must accept an electron before its outermost shell is filled.
Isotopes are atoms of the same element that have different numbers of protons. True False
False
Most liquids become less dense upon solidification, but water is different in that it becomes denser when it solidifies. True False
False
Free radicals contain unpaired electrons in their outermost energy shell, so they react readily with other atoms or molecules to reach a more stable state. Which of the following could potentially be a free radical? Magnesium (atomic number 12) Neon (atomic number 10) Fluorine (atomic number 9) Helium (atomic number 2)
Fluorine (atomic number 9)
Different types of living matter often have different forms of the same elements in their bodies. For example, the nitrogen in an animal often has a slightly different atomic structure than the nitrogen in a plant. Recently, nutritionists have discovered how to deduce the diets of various animal species by examining the type of nitrogen (and other elements) inside their bodies. What is the chemical basis behind this scenario? Isotopes of the same element have the same atomic number but different atomic masses. Covalent bonds result when two atoms share electrons. Hydrophobic interactions keep water molecules from forming bonds with fats and oils. Radioactive elements can be used to trace the paths of molecules through the body. Antioxidants buffer the potential damage that free radicals do to cells.
Isotopes of the same element have the same atomic number but different atomic masses.
What is meant by the statement that water has a high specific heat? It grows hot quickly. Water freezes easily. It can absorb a lot of energy without changing temperature. Water can heat up to only a certain temperature. The boiling point of water is low.
It can absorb a lot of energy without changing temperature.
For an atom to achieve maximum stability and become chemically inert, what must occur? Its outermost energy shell must be completely filled with electrons. Electron pairs are shared. The number of electrons must equal the number of protons. Ionization occurs.
Its outermost energy shell must be completely filled with electrons.
Which of the following is LEAST affected by the presence of water? Electron-proton interaction Polar covalent bond Nonpolar covalent bond Hydrogen bond Ionic bond
Nonpolar covalent bond
In general, a substance that carries an electric charge can dissolve in water. Given this fact, which of the following would most likely NOT dissolve in water? NaCl Ionic compounds Polar covalent molecules Nonpolar molecules
Nonpolar molecules
If you examined the human body on a chemical composition basis, which of the following combinations of elements would be most common? O, C, H, N C, N, Ca, S O, C, P, S C, H, Ca, Cl O, C, N, Na
O, C, H, N
Which of these atoms would become inert if it accepted three electrons? Carbon Oxygen Phosphorus Calcium
Phosphorus
Which of the following results from an unequal sharing of electrons between atoms? Polar covalent bond Nonpolar covalent bond Hydrogen bond Ionic bond Electron-proton interaction
Polar covalent bond
Sulfur is an essential element in the human body, and studying its characteristics is important in understanding human physiology. Sulfur atoms have six electrons in their outer shell. Based on this information, which of the following is TRUE? Sulfur can form important molecules using covalent bonds. Sulfur has eight electrons in its outer shell. Sulfur is an important isotope of hydrogen. Sulfur is inert.
Sulfur can form important molecules using covalent bonds.
What happens when hydrochloric acid (HCl) dissociates in pure water? The water has a decrease of H+ ions. The pH of the solution increases. The concentration of OH- ions increases. The HCl molecules separate into H+ and Cl- ions. The HCl molecules float on top of the water.
The HCl molecules separate into H+ and Cl- ions.
Imagine that you have been hired as a chemist and your first task is to examine a newly discovered atom. The paperwork you are given states that its atomic number is 110. What does this mean? The atom is an isotope. The atom contains 55 protons and 55 neutrons. The atom contains 55 electrons. The atom contains 110 protons.
The atom contains 110 protons.
Which of the following best explains why a particular atom may not form compounds easily? The atom's outer energy shells are completely full. The atom has seven electrons in its outer shell. The atom has an uneven number of protons. The atom has no electrons.
The atom's outer energy shells are completely full.
Which of the following is an example of hydrogen bonding? The bond between H of one water molecule and H of a separate water molecule The bond between O of one water molecule and O of a separate water molecule The bond between O and H in a single molecule of water The bond between O of one water molecule and H of a separate water molecule The bond between the H of a water molecule and H of a hydrogen molecule
The bond between O of one water molecule and H of a separate water molecule
Phosphorus has an atomic number of 15, so what is the distribution of its electrons? The first energy level has 2, the second has 8, and the third has 5. The first energy level has 8 and the second has 7. The electron arrangement cannot be determined from the atomic number alone. The first, second, and third energy levels have 5 electrons each. The first energy level has 2 and the second has 13.
The first energy level has 2, the second has 8, and the third has 5.
An atom of nitrogen attracts electrons more strongly than an atom of hydrogen. In an ammonia molecule (NH3), which of the following best describes the electrical charge of the individual atoms? The nitrogen is slightly positive. The nitrogen is slightly more negative. The hydrogens are strongly negative. Charges balance out and none of the atoms has any charge. The nitrogen becomes neutral.
The nitrogen is slightly more negative.
You drop a handful of common table salt into a glass of water. Which of the following best describes what is happening inside the glass at the molecular level? Water and sodium form a covalent bond. The positively charged hydrogen ends of the water molecules are attracted to sodium ions. Sodium and chloride ions form a covalent bond. The positively charged hydrogen ends of the water molecules are attracted to chloride ions.
The positively charged hydrogen ends of the water molecules are attracted to chloride ions.
Carbon-14 is often used for carbon dating, where scientists measure the rate of carbon-14 decay to determine the age of items. Carbon-14 contains six protons and eight neutrons. During the process of carbon-14 decay, one of its eight neutrons becomes a proton and an electron is emitted. Which of the following is the best explanation of what has occurred? The resulting atom is now a different element because the number of protons has changed. The resulting atom has a more stable nucleus. The resulting atom is still carbon-14. An ionic bond has formed.
The resulting atom is now a different element because the number of protons has changed.
Which statement is an accurate description of water molecules? They are ionically bonded. They are charged and nonpolar. They are uncharged and nonpolar. They are slightly charged and polar.
They are slightly charged and polar.
Acids have pH values below 7, whereas bases have pH values above 7. True False
True
Every atom of the same element has an equal number of electrons and protons. True False
True
To maintain a constant pH, buffers act to either accept or release H+. True False
True
All animals need oxygen gas (O2) for their primary cellular-level functioning. Inside the cell, O2 is split apart into oxygen atoms. Eventually, electrons that are flowing through the cell will be "received" by this oxygen. But first, the electrons combine with protons present in the cell to form a basic element that has a single proton and a single electron. Then this element combines with the oxygen to form a certain chemical compound. In this scenario, what chemical compound is produced when this element combines with oxygen? Bicarbonate (HCO3) Water (H2O) Carbon dioxide (CO2) Ozone (O3)
Water (H2O)
Imagine that you are trying to make a homemade salad dressing and place several drops of olive oil into a container of water. You stir the solution, but the oil doesn't readily mix. Instead, you observe a glistening clump of oil floating on the surface. Explain what is happening at the molecular level. (Your answer should include the term hydrophobic.)
When oil molecules are together in water, their nonpolar surfaces are hydrophobic and nestle together. They are surrounded by water molecules that form hydrogen bonds with one another but not with the oil.
The specific heat of water is 10 times greater than that of iron. You place a metal pot full of water on the stove to heat it up. You touch the metal handle of the pot when the water is still only lukewarm. Which of the following best describes what happens? You burn your finger and pull your hand away from the hot metal handle. You find that the handle is cooler than the water in the pot. You find that both the water and the handle are the same temperature. You determine that metal pots full of water produce acids and bases.
You burn your finger and pull your hand away from the hot metal handle.
For ice to melt, it has to absorb heat from its surroundings. become less dense. increase its heat of vaporization. increase its property of cohesion.
absorb heat from its surroundings.
Most biological molecules are joined by covalent bonds. ionic bonds. disulfide bonds. peptide bonds. hydrogen bonds.
covalent bonds.
A substance with specific properties that cannot be broken down or converted into another substance is called a(n) compound. ion. element. mixture. molecule.
element.
Water molecules are cohesive because they are repelled by nonpolar molecules. stick to other polar molecules. form hydrogen bonds. make up 60% to 90% of an organism's body weight. contain protons.
form hydrogen bonds.
The element carbon has atomic number 6. Carbon most likely shares two electrons with another atom. forms ionic bonds with other atoms. donates two electrons to another atom. forms four covalent bonds.
forms four covalent bonds.
The formation of ions involves the sharing of electrons. gain or loss of neutrons. gain or loss of protons. sharing of protons. gain or loss of electrons.
gain or loss of electrons.
Unlike a rock, a reptile can sit in the hot sunshine without its body temperature soaring quickly. This is because the water in its body is a good solvent. is a poor solvent. has a high specific heat. has a low specific heat.
has a high specific heat.
A neutral solution has a pH of 0. is hydrophobic. has no H+. has equal amounts of H+ and OH-. has no OH-.
has equal amounts of H+ and OH-.
If a substance measures 7 on the pH scale, that substance probably lacks OH- ions. has a higher concentration of OH- than H+ ions. has equal concentrations of H+ and OH- ions. may be lemon juice. is basic.
has equal concentrations of H+ and OH- ions.
Polar molecules have an equal distribution of electric charge. have an overall positive electric charge. are always ions. have an overall negative electric charge.
have an overall negative electric charge.
What type of bonding exists between the slight positive charge of a hydrogen atom and the slight negative charge of a nearby oxygen atom?
hydrogen bonding
Ions and polar molecules that are electrically attracted to water molecules are ________.
hydrophilic
If a certain atom has a tendency to lose two electrons, that atom can then become a(n) isotope. water molecule. polar molecule. ion.
ion
Atoms or molecules that have gained or lost electrons are called bases. buffers. ions. covalent. acids.
ions
Milk of magnesia is often used to treat stomach upset. It has a pH of 10. Based on this information, milk of magnesia is an acid. is hydrophobic. has the same pH as stomach acid. is a base.
is a base.
The atomic number of hydrogen is 1. Based on this fact, all of the following must be true of hydrogen gas (H2) EXCEPT that it uses covalent bonds to form the molecule. is a stable molecule. shares one pair of electrons between the two hydrogen atoms. is a polar molecule.
is a polar molecule.
An atom's nucleus is composed of protons only. protons and neutrons. protons and electrons. neutrons only. neutrons and electrons.
protons and neutrons.
If you place a paper towel in a dish of water, the water will move away from the towel because water molecules have hydrophobic interactions. dissolve the towel because water is a good solvent. separate into H+ and OH- ions, which will react with the paper towel molecules. move up the towel because water molecules move quickly as it vaporizes. move up the towel as the water adheres to the paper towel while the cohesive water molecules stay bound to each other.
move up the towel as the water adheres to the paper towel while the cohesive water molecules stay bound to each other.
Isotopes are atoms of the same element that have different numbers of ________.
neutrons
The atomic number of an atom is defined as the number of electrons in the outermost energy level. number of neutrons in the atomic nucleus. number of protons in the atomic nucleus. total number of electrons and neutrons. total number of energy shells.
number of protons in the atomic nucleus.
The fact that salt dissolves in water is best explained by the polar nature of water molecules. hydrophobic nature of the water. slightly charged nature of water molecules. hydrophobic nature of salt. ionic nature of water molecules.
polar nature of water molecules.
