Water and Carbon

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AP Biology › Water and Carbon

Questions 1 - 10
1

In reference to water, what to do cohesion, surface tension, and adhesion all have in common?

All are properties related to hydrogen bonding

All are results of the structure of hydrogen atoms

All are aspects of a crystalline structure

All are produced by covalent bonding

All are produced by ionic bonding

Explanation

These properties of water are all a result of hydrogen bonding. Hydrogen bonds result from the electrical attraction between partially positive hydrogen atoms and partially negative oxygen atoms of adjacent water molecules. The differences in electronegativity between hydrogen and oxygen give rise to the hydrogen bonding and associated properties.

Attraction and polarity in water molecules cause them to "stick" to one another. Attraction between water molecules results in cohesion, and attraction between the water molecules and other compounds in the environment results in adhesion. The high surface tension of water is caused by the "sticking" of water molecules to one another, which keep vapor pressure low.

Hydrogen bonding is a temporary intermolecular force, and is different from covalent or ionic bonding. Covalent and ionic bonding result in permanently joined atoms to build molecular structures.

2

In reference to water, what to do cohesion, surface tension, and adhesion all have in common?

All are properties related to hydrogen bonding

All are results of the structure of hydrogen atoms

All are aspects of a crystalline structure

All are produced by covalent bonding

All are produced by ionic bonding

Explanation

These properties of water are all a result of hydrogen bonding. Hydrogen bonds result from the electrical attraction between partially positive hydrogen atoms and partially negative oxygen atoms of adjacent water molecules. The differences in electronegativity between hydrogen and oxygen give rise to the hydrogen bonding and associated properties.

Attraction and polarity in water molecules cause them to "stick" to one another. Attraction between water molecules results in cohesion, and attraction between the water molecules and other compounds in the environment results in adhesion. The high surface tension of water is caused by the "sticking" of water molecules to one another, which keep vapor pressure low.

Hydrogen bonding is a temporary intermolecular force, and is different from covalent or ionic bonding. Covalent and ionic bonding result in permanently joined atoms to build molecular structures.

3

Which phase of water in the most dense?

Liquid

Solid

Gas

Supercritical fluid

Water has the same density in any of its phases

Explanation

Water, unlike many other compounds, has several special properties due to its hydrogen bonding between molecules. The hydrogen bonds are relatively strong, leading water to have very low vapor pressure and high surface tension. A side effect of the hydrogen bonding, however, is that when water crystallizes, the molecules will inevitably align so that the hydrogen bonds are maintained. The solid lattice structure of water molecules is, thus, not very tightly packed. The structure is ideal to optimize intermolecular forces, rather than space and volume. The density of the solid (ice) is thus less than the density of the liquid water.

Water vapor (gas) and supercritical water both have lower densities than ice, making liquid water the most dense.

4

Which phase of water in the most dense?

Liquid

Solid

Gas

Supercritical fluid

Water has the same density in any of its phases

Explanation

Water, unlike many other compounds, has several special properties due to its hydrogen bonding between molecules. The hydrogen bonds are relatively strong, leading water to have very low vapor pressure and high surface tension. A side effect of the hydrogen bonding, however, is that when water crystallizes, the molecules will inevitably align so that the hydrogen bonds are maintained. The solid lattice structure of water molecules is, thus, not very tightly packed. The structure is ideal to optimize intermolecular forces, rather than space and volume. The density of the solid (ice) is thus less than the density of the liquid water.

Water vapor (gas) and supercritical water both have lower densities than ice, making liquid water the most dense.

5

Water's ability to create intermolecular hydrogen bonds results in its inability to break up which of the following compounds?

Lipids

Ions

Amino acids

Sugars

Explanation

Nonpolar compounds will not be adequately dissolved in aqueous solutions. Lipids are nonpolar compounds that are mainly insoluble in water. This causes lipids to congregate together, rather than be broken apart in aqueous solutions. Lipids will generally come together to form globs or balls called micelles.

Ions, amino acids, and sugars (carbohydrates) are all polar, and will be adequately dissolved and ionized by water.

6

Which of the following is not considered a major component (element) of life?

Iron

Carbon

Oxygen

Sulfur

Nitrogen

Explanation

Iron is important for many organisms but it isn't found in quantities large enough for it to be a major component. It is part of the trace minerals. Carbon, nitrogen, sulfur and oxygen are all part of the bulk elements, elements that are found in the largest quantities (they make up 96% of organisms).

7

Water's ability to create intermolecular hydrogen bonds results in its inability to break up which of the following compounds?

Lipids

Ions

Amino acids

Sugars

Explanation

Nonpolar compounds will not be adequately dissolved in aqueous solutions. Lipids are nonpolar compounds that are mainly insoluble in water. This causes lipids to congregate together, rather than be broken apart in aqueous solutions. Lipids will generally come together to form globs or balls called micelles.

Ions, amino acids, and sugars (carbohydrates) are all polar, and will be adequately dissolved and ionized by water.

8

Which of the following is not considered a major component (element) of life?

Iron

Carbon

Oxygen

Sulfur

Nitrogen

Explanation

Iron is important for many organisms but it isn't found in quantities large enough for it to be a major component. It is part of the trace minerals. Carbon, nitrogen, sulfur and oxygen are all part of the bulk elements, elements that are found in the largest quantities (they make up 96% of organisms).

9

Which property or properties of water is/are most important for water transport in plants?

Cohesion and adhesion

High heat capacity

Universal solvent

Low density of solid water (ice)

Polarity

Explanation

Adhesion refers to the attraction between water molecules and foreign particles or surfaces. Cohesion refers to the attraction between one water molecule and another.

Adhesion of water to the cell walls of the xylem vessels and cohesion of water molecules to one another allow for water transport in plants. This is also known as capillary action.

The high heat capacity, low solid density, and polarity of water, as well as its use as a solvent, are all essential to the role of water in supporting life in other ways.

10

Which property or properties of water is/are most important for water transport in plants?

Cohesion and adhesion

High heat capacity

Universal solvent

Low density of solid water (ice)

Polarity

Explanation

Adhesion refers to the attraction between water molecules and foreign particles or surfaces. Cohesion refers to the attraction between one water molecule and another.

Adhesion of water to the cell walls of the xylem vessels and cohesion of water molecules to one another allow for water transport in plants. This is also known as capillary action.

The high heat capacity, low solid density, and polarity of water, as well as its use as a solvent, are all essential to the role of water in supporting life in other ways.

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