1.
Honey is composed mostly of glucose and fructose. What property of water explains why honey dissolves easily in water?
Correct Answer
C. Water is a polar molecule.
Explanation
Water is a polar molecule because it has a slightly positive charge on one end and a slightly negative charge on the other due to its bent shape and unequal distribution of electrons. This polarity allows water molecules to attract and interact with other polar molecules, such as glucose and fructose in honey. As a result, water can easily dissolve honey by surrounding and separating its individual molecules, breaking the attractive forces between them.
2.
Methane (CH4), oxygen (O2), and nitrogen (N2) are gases at room temperature. Water (H2O) has a similar molecular weight to these molecules. Why is H2O a liquid at room temperature?
Correct Answer
B. H2O has a high boiling point.
3.
Which of the following statements best describes how, in trees, water moves from the roots to the leaves?
Correct Answer
A. Transpiration from the leaves pulls water upward.
Explanation
Transpiration is the process by which water vapor is lost from the leaves through tiny pores called stomata. As water evaporates from the leaves, it creates a negative pressure, or tension, which pulls water molecules up through the xylem vessels in the stem and roots. This process is known as the cohesion-tension theory. Therefore, the statement "Transpiration from the leaves pulls water upward" best describes how water moves from the roots to the leaves in trees.
4.
Lamila wants to determine the rate at which a plant uses water. She fills a beaker with 80 mL of water and places a leafy flower stem into the beaker through a small opening in the beaker’s cap. Lamila then places the beaker near a sunny window. One week later, 47 mL of water remains in the beaker. What plant process best explains the loss of water in the beaker?
Correct Answer
D. Transpiration
Explanation
The best explanation for the loss of water in the beaker is transpiration. Transpiration is the process by which water is lost from the leaves of plants through small openings called stomata. When the plant is exposed to sunlight, it undergoes photosynthesis, which requires water. As a result, water is drawn up through the stem and leaves and is eventually lost through transpiration. This explains the decrease in water level in the beaker over time.
5.
Which of the following characteristics of water is not a result of hydrogen bonding?
Correct Answer
D. All of the answers are a result of hydrogen bonding
Explanation
All of the given characteristics of water - adhesive strength, capillarity, and cohesive strength - are a result of hydrogen bonding. Hydrogen bonding occurs between water molecules, leading to the cohesive forces that hold water molecules together and create surface tension. Adhesive strength refers to the ability of water to stick to other substances, which is also a result of hydrogen bonding. Capillarity, which allows water to move against gravity in narrow spaces, is possible due to the cohesive forces caused by hydrogen bonding. Therefore, all of the given answers are indeed a result of hydrogen bonding.
6.
Which of the following makes up a molecule of water?
Correct Answer
D. Two atoms of hydrogen and one atom of oxygen
Explanation
A molecule of water is made up of two atoms of hydrogen and one atom of oxygen. This is because the chemical formula for water is H2O, indicating that there are two hydrogen atoms bonded to one oxygen atom.
7.
Water molecules are polar, with the
Correct Answer
D. Oxygen side being slightly negative and the hydrogen side being slightly positive.
Explanation
Water molecules are polar because the oxygen atom attracts the shared electrons more strongly than the hydrogen atoms. This causes the oxygen side of the molecule to have a slight negative charge, while the hydrogen side has a slight positive charge.
8.
The cohesiveness between water molecules is due largely to:
Correct Answer
A. Hydrogen bonds.
Explanation
The cohesiveness between water molecules is due largely to hydrogen bonds. Hydrogen bonds are formed between the positively charged hydrogen atom of one water molecule and the negatively charged oxygen atom of another water molecule. These bonds are relatively weak individually, but when many hydrogen bonds are formed between water molecules, they create a strong cohesive force. This cohesive force allows water molecules to stick together, giving water its unique properties such as high surface tension and the ability to form droplets.
9.
A stalk of celery is placed in a solution of blue colored dye. After one hour, the leaves have blue fluid in their veins. Which property of water is being demonstrated?
Correct Answer
A. Adhesion and cohesion
Explanation
Adhesion and cohesion are being demonstrated in this scenario. Adhesion refers to the attraction between water molecules and other substances, in this case, the celery stalk. Cohesion refers to the attraction between water molecules themselves. The blue dye solution is able to adhere to the surface of the celery stalk, and the water molecules within the stalk are cohesive, allowing the blue fluid to be transported through the veins of the leaves.
10.
Which characteristic of water molecules directly contributes to the remarkable "water walking" success of the aquatic insects pictured in the accompanying figure?
Correct Answer
A. Hydrogen bonds
Explanation
Hydrogen bonds are the attractive forces between the positively charged hydrogen atom of one water molecule and the negatively charged oxygen atom of another water molecule. These bonds are responsible for the cohesive nature of water and give it its high surface tension. This surface tension allows certain insects to walk on water, as the hydrogen bonds create a strong enough force to support their weight. Capillary action, nonpolar covalent bonds, ionic bonds, and adhesive forces do not directly contribute to the water walking ability of these insects.
11.
Which property of water is described in the picture below?
Correct Answer
B. Surface tension
Explanation
The picture is likely showing water droplets forming a dome shape on a surface, which is a characteristic of surface tension. Surface tension is the property of a liquid that causes the molecules at the surface to be attracted to each other, creating a "skin" or "film" on the surface. This property allows insects to walk on water and for water to form droplets. Capillary action is the ability of a liquid to flow against gravity in a narrow space, transpiration is the process of water movement through a plant, and adhesion is the attraction between different substances.