Question
Where do hydrogen bonds form?
A. Between the slight negative charge of hydrogen and slight positive charge of oxygen within a water molecule
B. Between the slight positive charge of hydrogen and slight negative charge of oxygen within a water molecule
C. Between the slight positive charge of hydrogen and slight negative charge of oxygen in different water molecules
D. Between the slight negative charge of hydrogen and slight positive charge of oxygen in different water molecules
Answer/Explanation
Answer: C. Between the slight positive charge of hydrogen and slight negative charge of oxygen in different water molecules
Explanation:
Hydrogen bonds are weak attractions that happen when a slightly positive hydrogen atom in one molecule is pulled toward a slightly negative atom (like oxygen) in a nearby molecule. In water, these bonds form between different water molecules — not within a single one — and they help explain why water sticks together so well.
Evaluating the options:
A. Incorrect – This says hydrogen is slightly negative and oxygen is slightly positive, which is the opposite of true. Also, hydrogen bonds don’t happen inside a single molecule.
B. Incorrect – The charges are right (hydrogen is slightly positive, oxygen is slightly negative), but this describes a bond within one water molecule. Hydrogen bonds happen between different molecules.
C. Correct – This is exactly right. Hydrogen bonds form between the slightly positive hydrogen of one water molecule and the slightly negative oxygen of another water molecule.
D. Incorrect – This reverses the charges. Hydrogen is not slightly negative, and oxygen is not slightly positive. That’s not how water molecules interact.
Question
What are linked by hydrogen bonds?
A. Hydrogen and oxygen within a water molecule
B. Phosphate and sugar within a DNA molecule
C. Base and sugar between DNA nucleotides
D. Hydrogen and oxygen in different water molecules
Answer/Explanation
Answer: D. Hydrogen and oxygen in different water molecules
Explanation:
Hydrogen bonds are weak attractions between a slightly positive hydrogen atom and a slightly negative atom (like oxygen or nitrogen) in a different molecule or in a different part of a large molecule. They don’t form inside single small molecules like water, but they do help hold water molecules together and hold DNA strands together.
Evaluating the options:
A. Incorrect – Hydrogen and oxygen within a water molecule are joined by a covalent bond, not a hydrogen bond.
B. Incorrect – Phosphate and sugar in DNA are linked by covalent bonds, which are strong chemical bonds, not hydrogen bonds.
C. Incorrect – The base and sugar in DNA are also connected by covalent bonds, not hydrogen bonds.
D. Correct – Hydrogen bonds form between the slightly positive hydrogen in one water molecule and the slightly negative oxygen in another water molecule.
Correct answer: D. Hydrogen and oxygen in different water molecules
Question
Between which atoms do hydrogen bonds form in water?
A. Oxygen and hydrogen atoms in the same water molecule
B. Oxygen and hydrogen atoms in different water molecules
C. Hydrogen atoms in the same water molecule
D. Oxygen atoms of different water molecules
▶️Answer/Explanation
Answer: B. Oxygen and hydrogen atoms in different water molecules
In water, each molecule has a slightly positive hydrogen atom and a slightly negative oxygen atom. A hydrogen bond forms between the hydrogen atom of one water molecule and the oxygen atom of another water molecule. These weak attractions help water molecules stick together and give water its unique properties like surface tension and high boiling point.
Evaluating the options:
A. Incorrect – The bond between oxygen and hydrogen in the same water molecule is a covalent bond, not a hydrogen bond.
B. Correct – This is the correct answer. Hydrogen bonds form between the slightly positive hydrogen atom of one water molecule and the slightly negative oxygen atom of another water molecule.
C. Incorrect – Hydrogen atoms don’t form hydrogen bonds with each other in water. Hydrogen bonds involve one hydrogen and one more electronegative atom (like oxygen).
D. Incorrect – Hydrogen bonds do not form directly between two oxygen atoms. The bond is between a hydrogen and an oxygen from different molecules.
Question
What property of water accounts for its usefulness as a coolant in sweat?
A. High specific heat capacity
B. High latent heat of vaporization
C. High boiling point
D. High melting point
Answer/Explanation
Answer: B. High latent heat of vaporization
Water helps cool the body through evaporation of sweat. The key property here is its high latent heat of vaporization, which means it takes a lot of heat energy to change water from a liquid to a gas. As sweat evaporates from the skin, it absorbs heat from the body, cooling it down. This is why sweating is an effective cooling mechanism.
Evaluating the options:
A. Incorrect – High specific heat capacity means water resists temperature change, which helps regulate body temperature overall, but it’s not the main reason water cools the body when sweat evaporates.
B. Correct – Water’s high latent heat of vaporization means it absorbs a lot of heat when it evaporates, which removes heat from the body. This is exactly how sweat cools us down.
C. Incorrect – High boiling point means water stays liquid over a wide range of temperatures, but it doesn’t directly explain the cooling effect of sweating.
D. Incorrect – High melting point means water freezes at a relatively high temperature (0°C), but that has nothing to do with sweating or cooling.
Question
The diagram shows water molecules.
Which property of water is not illustrated?
A. Cohesion
B. Dipolarity
C. Hydrogen bonding
D. Adhesion
▶️Answer/Explanation
Answer: D. Adhesion
Explanation:
Water has several important properties:
- Cohesion is water molecules sticking to each other due to hydrogen bonds.
- Dipolarity means water has a positive end (hydrogen) and a negative end (oxygen), making it a polar molecule.
- Hydrogen bonding is the weak attraction between the positive hydrogen of one molecule and the negative oxygen of another.
- Adhesion is water sticking to other surfaces or substances.
Evaluating the options:
A. Incorrect – Cohesion is a common property of water and often illustrated by water molecules sticking together.
B. Incorrect – Dipolarity is fundamental to water’s behavior and is usually shown by the separation of charges in the molecule.
C. Incorrect – Hydrogen bonding is central to many water properties and is frequently illustrated.
D. Correct – This refers to water sticking to other surfaces or substances. Since the diagram only shows water molecules (H and O), no other surfaces or molecules are present to demonstrate adhesion.
Question
What is the benefit to living organisms that water has a high specific heat capacity?
A. Heat can be lost from the skin when sweat evaporates.
B. Aquatic environments do not have a great fluctuation in their temperature.
C. The amount of heat stored by water is highly predictable.
D. It allows water to be a solvent for chemical reactions at body temperature.
▶️Answer/Explanation
Answer: B. Aquatic environments do not have a great fluctuation in their temperature.
Explanation:
High specific heat capacity means water can absorb or release a large amount of heat with only a small change in its own temperature. This property helps living things maintain stable internal and environmental temperatures, which is important for proper enzyme function and overall survival.
Evaluating the options:
A. Incorrect – This describes heat loss through evaporation, which relates to water’s high latent heat of vaporization, not specific heat capacity.
B. Correct – Because water resists temperature changes, aquatic environments stay relatively stable and don’t fluctuate widely in temperature, benefiting organisms living there.
C. Incorrect – While heat storage in water is relatively consistent, this is not the main benefit related to living organisms.
D. Incorrect – Water’s role as a solvent is due to its polarity, not its specific heat capacity
Question
What is a property of water?
A. Water has a low specific heat capacity so large increases in heat energy cause a small temperature change.
B. Water is an excellent solvent for non-polar substances.
C. Covalent bonds between adjacent water molecules are responsible for its unique properties.
D. Water molecules are highly cohesive which is important for transport in xylem.
▶️Answer/Explanation
Answer: D. Water molecules are highly cohesive which is important for transport in xylem.
Explanation:
Water has several unique properties due to its molecular structure. Its molecules are polar, meaning one side (oxygen) is slightly negative and the other side (hydrogen) is slightly positive. This polarity allows water molecules to form hydrogen bonds with each other, making water highly cohesive. Cohesion helps water move up plants through the xylem.
Evaluating the options:
A. Incorrect – Water actually has a high specific heat capacity, meaning it takes a lot of heat energy to change its temperature, not a low one.
B. Incorrect – Water is an excellent solvent for polar substances and ions, but not for non-polar substances like oils.
C. Incorrect – The bonds between water molecules are hydrogen bonds, not covalent bonds. Covalent bonds occur within a single water molecule, between hydrogen and oxygen atoms.
D. Correct – Water molecules are highly cohesive because of hydrogen bonding, which is important for the upward transport of water in plant xylem vessels.