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1.1 Structure of Water and Hydrogen Bonding

4 min readdecember 27, 2022

Danna Esther Gelfand

Danna Esther Gelfand

Jillian Holbrook

Jillian Holbrook

Danna Esther Gelfand

Danna Esther Gelfand

Jillian Holbrook

Jillian Holbrook

Water Molecules

Water is a , meaning the ends have opposite partial charges or unequal distribution of charge. The of water H2O tells us that a water molecule is made up of two hydrogens and one . Water is polar because the hydrogens carry partial positive charges, and has a , which we can examine further when we discuss .

The simple phrase, "like attracts like," helps us to remember that polar substances are attracted to other polar substances, just as nonpolar substances are attracted to other nonpolar substances. Ever tried mixing oil and water? Oil molecules are nonpolar and have equally balanced charges rather than positive and negative poles like water. Because of this, oil and water are immiscible or do not combine. Polar and nonpolar do not attract because they are not alike.

In regard to water, there is specific terminology to describe attractive interactions. A hydrophilic substance has an affinity for water, which means it attracts water. Conversely, a hydrophobic substance is one that avoids water or does not have an affinity for water. For example, are hydrophobic because they have relatively nonpolar bonds, while water is polar. Water is the most common molecule in living organisms, so it is important that we understand its interactions.

Hydrogen Bonding

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-zL6dLkQO2b0y.jpg?alt=media&token=9372bf5f-5159-4567-af75-223f3d134085

Image Credit: Chemicool

is a type of chemical intermolecular bond that occurs when a atom bonds to a highly , including , nitrogen, and fluorine. This creates a in the molecule, where the carries a , and the has a —the type of structure we observed that gives water its polarity, as bond together through . bonds are generally weaker than , but they are still relatively strong and play an important role in many chemical and biological processes.

In biology, is critical, as occurs in many different types of molecules, including water, DNA, and proteins. is responsible for many molecular properties, such as the shape and function of proteins, the stability of many chemical compounds, and the formation of intermolecular interactions in crystalline solids. bonds between give water the properties of , , , , and .

Properties of Water

1. : the attraction of . Strong cohesive forces are present because they form bonds with each other.

  • Example: due to contributes to the transport of water and nutrients against gravity in plants. is the loss of water from a plant in the form of water vapor.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Ftranspiration_water_cycle_rgb_p.png?alt=media&token=a090b121-e095-474a-8c29-c68fe48cde24

Image courtesy of ABCteach.

2. : when one substance is attracted to another. Water adheres to other molecules and surfaces.

  • Example: water on a glass surface, like a window or windshield.

3. : difficulty to break the surface of the water because of cohesive forces.

  • Example: water strider insects rely on to stay afloat and walk on the surface of bodies of freshwater.

4. : the amount of heat energy it takes to raise or lower the temperature of one gram of a substance by one degree Celsius. Water has a high , so it can absorb or release a large amount of heat with only a slight change in its own temperature so large bodies of water take a while to evaporate.

5. : water has a high heat of vaporization, so the water can absorb a lot of heat and leave the surface cooler.

  • Example: excess body heat is used to convert beads of sweat/perspiration into vapor, which cools down the body

6. : shifts from one water molecule to another.

  • When a molecule is increasing by releasing into solutions, it is an . (Ex. HCl ➡️ H+ + Cl-)

  • When a molecule is increasing hydroxide concentration by absorbing or accepting , it is a . (Ex: NaOH ➡️ Na+ + OH-) 

The counterbalance of hydronium and hydroxide results in water having a of 7.0, meaning it is neither acidic nor basic.

  • range (0-14): acidic (< 7), neutral (7), alkaline/basic (> 7). Each level on the is a ten-fold change because the is . Most biological fluids are in the pH range of 6-8. pH = −log [H+]


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Key Terms to Review (28)

Acid

: An acid is any substance that donates protons or hydrogen ions to an aqueous solution, thereby increasing the hydronium ion concentration.

Adhesion

: Adhesion is the attraction between different types of molecules.

Base

: A base is a substance that can accept protons or donate a pair of valence electrons. In the context of biology, bases often refer to substances that can accept hydrogen ions and have a pH value greater than 7.

Chemical Formula

: A chemical formula represents the proportion of atoms per element that make up a chemical compound using symbols from the periodic table.

Cohesion

: Cohesion refers to the tendency for particles or molecules of the same substance to stick together.

Covalent Bonds

: Covalent bonds are chemical bonds formed by sharing pairs of electrons between atoms.

Dipole Moment

: A dipole moment is a measure of the polarity of a molecule, indicating how much positive and negative charge is separated within the molecule.

Dissociation of Water

: The dissociation of water refers to the breaking down of H2O molecules into ions - specifically, one hydrogen ion (H+) and one hydroxide ion (OH-).

Electronegative Atom

: An electronegative atom has a high affinity for electrons, meaning it has a tendency to attract shared electrons in a covalent bond towards itself.

Evaporative Cooling

: Evaporative cooling is a process where the surface of an object becomes cooler during evaporation. This happens because the molecules with the highest kinetic energy are most likely to evaporate, leaving behind molecules with lower average kinetic energy and thus reducing temperature.

Hydrogen

: Hydrogen is the first element on the periodic table. It's a colorless, odorless, tasteless gas that's highly flammable and combines with oxygen to form water.

Hydrogen bonding

: Hydrogen bonding is a special type of intermolecular attraction between the hydrogen atom in a polar bond (particularly H-F, H-O, and H-N) and an electronegative atom nearby.

Hydrogen Ions

: Hydrogen ions (H+) are single proton with no electrons and play crucial roles in chemical reactions, especially those involving acids and bases.

Hydronium Concentration

: The hydronium concentration, often represented as [H3O+], is the measure of the amount of hydronium ions in a solution. It's used to determine the acidity or alkalinity (pH) of a solution.

Hydrophilic Substance

: A hydrophilic substance is one that has an affinity for water; it can dissolve in or mix well with water.

Hydrophobic Substance

: A hydrophobic substance is one that does not have an affinity for water; it does not dissolve in or mix well with water.

Lipids

: Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids. They are an important part of living cells and serve as energy storage.

Logarithmic

: In the context of biology, a logarithmic scale is often used to represent data that covers a large range of values in a compact way. It's a mathematical concept where each increment on the axis increases by a factor of 10.

Neutral pH

: A neutral pH value is 7 on the pH scale, indicating neither acidity nor basicity. Pure water has a neutral pH.

Oxygen

: Oxygen is a chemical element with symbol O and atomic number 8. It's essential for life on earth because it's part of the air we breathe and water we drink.

Partial Negative Charge

: A partial negative charge occurs when an atom in a molecule attracts electrons more strongly than other atoms, causing the electrons to spend more time near that atom and giving it a slight negative charge.

Partial Positive Charge

: This occurs when an atom shares its electron unequally with another atom in covalent bonding. The atom that pulls less strongly on shared electrons has partial positive charge due to lack of electron density.

pH Scale

: The pH scale measures how acidic or basic an aqueous solution is, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral.

Polar Molecule

: A polar molecule has uneven distribution of charge, meaning it has both positive and negative regions due to differences in electronegativity among its atoms.

Specific Heat

: Specific heat refers to the amount of heat energy required to raise one gram of substance by one degree Celsius.

Surface Tension

: Surface tension refers to the cohesive force at the surface of a liquid that allows it to resist external forces.

Transpiration

: Transpiration is essentially plant sweat; it's when water vapor escapes from plants into the atmosphere through tiny pores called stomata.

Water Molecules

: A water molecule is a chemical compound made up of two hydrogen atoms bonded to one oxygen atom. It's the most abundant molecule on Earth's surface.

1.1 Structure of Water and Hydrogen Bonding

4 min readdecember 27, 2022

Danna Esther Gelfand

Danna Esther Gelfand

Jillian Holbrook

Jillian Holbrook

Danna Esther Gelfand

Danna Esther Gelfand

Jillian Holbrook

Jillian Holbrook

Water Molecules

Water is a , meaning the ends have opposite partial charges or unequal distribution of charge. The of water H2O tells us that a water molecule is made up of two hydrogens and one . Water is polar because the hydrogens carry partial positive charges, and has a , which we can examine further when we discuss .

The simple phrase, "like attracts like," helps us to remember that polar substances are attracted to other polar substances, just as nonpolar substances are attracted to other nonpolar substances. Ever tried mixing oil and water? Oil molecules are nonpolar and have equally balanced charges rather than positive and negative poles like water. Because of this, oil and water are immiscible or do not combine. Polar and nonpolar do not attract because they are not alike.

In regard to water, there is specific terminology to describe attractive interactions. A hydrophilic substance has an affinity for water, which means it attracts water. Conversely, a hydrophobic substance is one that avoids water or does not have an affinity for water. For example, are hydrophobic because they have relatively nonpolar bonds, while water is polar. Water is the most common molecule in living organisms, so it is important that we understand its interactions.

Hydrogen Bonding

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-zL6dLkQO2b0y.jpg?alt=media&token=9372bf5f-5159-4567-af75-223f3d134085

Image Credit: Chemicool

is a type of chemical intermolecular bond that occurs when a atom bonds to a highly , including , nitrogen, and fluorine. This creates a in the molecule, where the carries a , and the has a —the type of structure we observed that gives water its polarity, as bond together through . bonds are generally weaker than , but they are still relatively strong and play an important role in many chemical and biological processes.

In biology, is critical, as occurs in many different types of molecules, including water, DNA, and proteins. is responsible for many molecular properties, such as the shape and function of proteins, the stability of many chemical compounds, and the formation of intermolecular interactions in crystalline solids. bonds between give water the properties of , , , , and .

Properties of Water

1. : the attraction of . Strong cohesive forces are present because they form bonds with each other.

  • Example: due to contributes to the transport of water and nutrients against gravity in plants. is the loss of water from a plant in the form of water vapor.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2Ftranspiration_water_cycle_rgb_p.png?alt=media&token=a090b121-e095-474a-8c29-c68fe48cde24

Image courtesy of ABCteach.

2. : when one substance is attracted to another. Water adheres to other molecules and surfaces.

  • Example: water on a glass surface, like a window or windshield.

3. : difficulty to break the surface of the water because of cohesive forces.

  • Example: water strider insects rely on to stay afloat and walk on the surface of bodies of freshwater.

4. : the amount of heat energy it takes to raise or lower the temperature of one gram of a substance by one degree Celsius. Water has a high , so it can absorb or release a large amount of heat with only a slight change in its own temperature so large bodies of water take a while to evaporate.

5. : water has a high heat of vaporization, so the water can absorb a lot of heat and leave the surface cooler.

  • Example: excess body heat is used to convert beads of sweat/perspiration into vapor, which cools down the body

6. : shifts from one water molecule to another.

  • When a molecule is increasing by releasing into solutions, it is an . (Ex. HCl ➡️ H+ + Cl-)

  • When a molecule is increasing hydroxide concentration by absorbing or accepting , it is a . (Ex: NaOH ➡️ Na+ + OH-) 

The counterbalance of hydronium and hydroxide results in water having a of 7.0, meaning it is neither acidic nor basic.

  • range (0-14): acidic (< 7), neutral (7), alkaline/basic (> 7). Each level on the is a ten-fold change because the is . Most biological fluids are in the pH range of 6-8. pH = −log [H+]


-----

Key Terms to Review (28)

Acid

: An acid is any substance that donates protons or hydrogen ions to an aqueous solution, thereby increasing the hydronium ion concentration.

Adhesion

: Adhesion is the attraction between different types of molecules.

Base

: A base is a substance that can accept protons or donate a pair of valence electrons. In the context of biology, bases often refer to substances that can accept hydrogen ions and have a pH value greater than 7.

Chemical Formula

: A chemical formula represents the proportion of atoms per element that make up a chemical compound using symbols from the periodic table.

Cohesion

: Cohesion refers to the tendency for particles or molecules of the same substance to stick together.

Covalent Bonds

: Covalent bonds are chemical bonds formed by sharing pairs of electrons between atoms.

Dipole Moment

: A dipole moment is a measure of the polarity of a molecule, indicating how much positive and negative charge is separated within the molecule.

Dissociation of Water

: The dissociation of water refers to the breaking down of H2O molecules into ions - specifically, one hydrogen ion (H+) and one hydroxide ion (OH-).

Electronegative Atom

: An electronegative atom has a high affinity for electrons, meaning it has a tendency to attract shared electrons in a covalent bond towards itself.

Evaporative Cooling

: Evaporative cooling is a process where the surface of an object becomes cooler during evaporation. This happens because the molecules with the highest kinetic energy are most likely to evaporate, leaving behind molecules with lower average kinetic energy and thus reducing temperature.

Hydrogen

: Hydrogen is the first element on the periodic table. It's a colorless, odorless, tasteless gas that's highly flammable and combines with oxygen to form water.

Hydrogen bonding

: Hydrogen bonding is a special type of intermolecular attraction between the hydrogen atom in a polar bond (particularly H-F, H-O, and H-N) and an electronegative atom nearby.

Hydrogen Ions

: Hydrogen ions (H+) are single proton with no electrons and play crucial roles in chemical reactions, especially those involving acids and bases.

Hydronium Concentration

: The hydronium concentration, often represented as [H3O+], is the measure of the amount of hydronium ions in a solution. It's used to determine the acidity or alkalinity (pH) of a solution.

Hydrophilic Substance

: A hydrophilic substance is one that has an affinity for water; it can dissolve in or mix well with water.

Hydrophobic Substance

: A hydrophobic substance is one that does not have an affinity for water; it does not dissolve in or mix well with water.

Lipids

: Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids. They are an important part of living cells and serve as energy storage.

Logarithmic

: In the context of biology, a logarithmic scale is often used to represent data that covers a large range of values in a compact way. It's a mathematical concept where each increment on the axis increases by a factor of 10.

Neutral pH

: A neutral pH value is 7 on the pH scale, indicating neither acidity nor basicity. Pure water has a neutral pH.

Oxygen

: Oxygen is a chemical element with symbol O and atomic number 8. It's essential for life on earth because it's part of the air we breathe and water we drink.

Partial Negative Charge

: A partial negative charge occurs when an atom in a molecule attracts electrons more strongly than other atoms, causing the electrons to spend more time near that atom and giving it a slight negative charge.

Partial Positive Charge

: This occurs when an atom shares its electron unequally with another atom in covalent bonding. The atom that pulls less strongly on shared electrons has partial positive charge due to lack of electron density.

pH Scale

: The pH scale measures how acidic or basic an aqueous solution is, ranging from 0 (very acidic) to 14 (very basic), with 7 being neutral.

Polar Molecule

: A polar molecule has uneven distribution of charge, meaning it has both positive and negative regions due to differences in electronegativity among its atoms.

Specific Heat

: Specific heat refers to the amount of heat energy required to raise one gram of substance by one degree Celsius.

Surface Tension

: Surface tension refers to the cohesive force at the surface of a liquid that allows it to resist external forces.

Transpiration

: Transpiration is essentially plant sweat; it's when water vapor escapes from plants into the atmosphere through tiny pores called stomata.

Water Molecules

: A water molecule is a chemical compound made up of two hydrogen atoms bonded to one oxygen atom. It's the most abundant molecule on Earth's surface.


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AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.


© 2024 Fiveable Inc. All rights reserved.

AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.