Chemical Bonds, Functional Groups, pH
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Questions and Answers

A water molecule has a linear shape due to the non-bonding electron pairs of the oxygen atom.

False (B)

Which factor does NOT contribute to the formation of hydrogen bonds?

  • High electronegativity of atoms like N, O, and F
  • Non-binding electron pairs
  • Dipole-dipole interactions
  • The quantity of metallic bonds (correct)

Water stabilizes body temperature due to its high ______-capacity.

heat

What happens to the movement of water molecules below 0°C?

<p>Movement of water molecules slows down. (D)</p> Signup and view all the answers

Which of the following statements is correct about the density of water?

<p>The density of water decreases when it freezes. (D)</p> Signup and view all the answers

Which statement describes the behavior of water when heated?

<p>It expands, and the movement of molecules becomes faster. (C)</p> Signup and view all the answers

Water is unable to dissolve other molecules.

<p>False (B)</p> Signup and view all the answers

Which characteristic describes molecules that are NOT soluble in lipid?

<p>Hydrophilic (B)</p> Signup and view all the answers

Aqueous solutions may be which of the following?

<p>All of the above (D)</p> Signup and view all the answers

What must be present in equal numbers for a solution to be considered neutral?

<p>Hydrogen ions (H+) and hydroxide ions (OH-) (B)</p> Signup and view all the answers

When a solution is more acidic, the pH increases and will be somewhere between 7 and 14.

<p>False (B)</p> Signup and view all the answers

On the pH scale, what range signifies an alkaline solution?

<p>7-14 (B)</p> Signup and view all the answers

Hydrogen bonds allow water to demonstrate both cohesion and adhesion.

<p>True (A)</p> Signup and view all the answers

Water molecules are strongly ______ to each other.

<p>attached</p> Signup and view all the answers

A large amount of ______ lets water absorb a large amount of heat without changing its state, e.g. from liquid to gas.

<p>heat</p> Signup and view all the answers

What property of water protects living organisms from rapid temperature changes?

<p>Temperature rises and falls slowly (D)</p> Signup and view all the answers

Changes in density based on temperature are similar to other compounds

<p>False (B)</p> Signup and view all the answers

Over what percentage of the planet is covered by water?

<p>70% (B)</p> Signup and view all the answers

Acting as a universal ______: water's solvency is related to the polarity.

<p>solvent</p> Signup and view all the answers

Cohesion enables hydrogen bonds to stick together, allowing chemical ______ to occur in organisms.

<p>reaction</p> Signup and view all the answers

Surface tension: water molecules at the surface are what?

<p>More tightly packed (D)</p> Signup and view all the answers

Match the following functional group with its correct characteristics:

<p>-OH = Occurs in alcohols as well as in carbohydrates. -CHO = May refer to different chemical groups -COOH = Tends to dissociate in aqueous solutions and acts as an acid -NH2 = Acts as bases in organic molecules</p> Signup and view all the answers

The phosphate group is what?

<p>Acidic (A)</p> Signup and view all the answers

The sulfhydryl or thiol group is the analog of what?

<p>Hydroxyl group (C)</p> Signup and view all the answers

Water has a ______ property, since oxygen has a much higher electron affinity than hydrogen.

<p>dipole</p> Signup and view all the answers

Water tends to dissociate into which ions?

<p>-OH and $H^+$ (D)</p> Signup and view all the answers

Molecules being not water-soluble are called hydrophilic.

<p>False (B)</p> Signup and view all the answers

Water can not passively move through semi-permeable membranes.

<p>False (B)</p> Signup and view all the answers

If the energy level of the joined compound is lower than the energy level of the separate atoms, a stable compound is created, call what?

<p>Molecule (D)</p> Signup and view all the answers

In the case of the covalent bond, what is the atoms doing?

<p>Shares electrons (D)</p> Signup and view all the answers

Covalent bonds can be?

<p>All of the above (D)</p> Signup and view all the answers

Adhesion is the ability to cling to other ______, because of these cohesive and adhesive properties.

<p>surfaces</p> Signup and view all the answers

Which of the functional groups decreases the $H^+$ concentration of the solutions and become protonated and consequently positively charged?

<p>Amino groups (A)</p> Signup and view all the answers

In an ionic bond, electrons are shared.

<p>False (B)</p> Signup and view all the answers

In metallic bonds, electrons are shared and occupy what?

<p>An electron orbital (B)</p> Signup and view all the answers

What are secondary-bonds?

<p>Weaker than strong primary bonds (D)</p> Signup and view all the answers

Bases taste sour.

<p>False (B)</p> Signup and view all the answers

Which taste would be used to describe an acid?

<p>Sour (A)</p> Signup and view all the answers

When a substance has a pH greater than 7 it is a acid.

<p>False (B)</p> Signup and view all the answers

According to pH level, what is consider to be neutral?

<p>7 (B)</p> Signup and view all the answers

How does water's high heat capacity contribute to the stability of body temperature in biological systems?

<p>By requiring a significant amount of energy to change temperature, buffering against drastic fluctuations (C)</p> Signup and view all the answers

Amino groups act as ______ in organic molecules and tend to ______ the $H^+$ concentration of the solutions.

<p>bases#decrease</p> Signup and view all the answers

Hydrophobic molecules, also known as lipophobic, readily dissolve in water due to their affinity for polar substances.

<p>False (B)</p> Signup and view all the answers

Contrast metallic and covalent bonds based on electron behavior and resultant conductivity.

<p>In metallic bonds, electrons are delocalized and shared among all metal atoms, resulting in high electrical conductivity. In covalent bonds, participant atoms share electrons to close the unclosed outer electron shells and reach the noble gas configuration, Electrons are more localized, leading to lower conductivity.</p> Signup and view all the answers

Match the following properties of water with their descriptions:

<p>Surface Tension = Water molecules at the surface are more tightly attached to each other and to the air above. High Heat Capacity = Water molecules can absorb a large amount of heat without changing its state. Density Anomaly = Water expands when it freezes, causing ice to float. Universal Solvent = Water's polarity allows it to dissolve many different substances.</p> Signup and view all the answers

Flashcards

Chemical Compound

Chemical compounds made of two or more atoms joined together.

Covalent Bond

A chemical bond where atoms share electrons.

Binding Electrons

Electrons involved in the covalent bond.

Lone Pair

A pair of non-bonding electrons.

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Sigma Bond (σ)

The first covalent bond between two atoms.

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Ionic Bond

Occurs between atoms tending to form oppositely charged ions.

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Metallic Bond

Occurs in metals; electrons are shared within the metal.

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Secondary Bonds

Weaker bonds, but important in structure/function of molecules.

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Dipole-Dipole

Occurs between molecules being dipoles.

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Hydrogen Bond

Chemical bond between hydrogen and other electronegative atoms.

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Chemical Groups

Determine chemical and physical properties of a molecule.

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Hydroxyl Group (-OH)

OH group characteristic of alcohols, increases water solubility.

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Carbonyl Group (-CHO)

CHO group, can be aldehyde or ketone-depending on position.

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Carboxyl Group R-COOH

Tends to dissociate in aqueous solutions and acts as acids.

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Amino Groups (-NH2)

Act as bases in organic molecules.

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Phosphate Group (-OPO3^2-)

Group found in sugar-phosphate backbone of nucleic acids.

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Sulfhydryl Group (-SH)

Analog of hydroxyl; thiol group present in methionine and cysteine.

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Water

The V-shaped molecule necessary for life.

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Dipole Property

Water molecules have a dipole property due to electron affinity.

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Three Forms of Matter

Water can be found in solid, liquid and gas forms.

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Dissociate into ions

Water tends to break apart into -OH and H+.

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High-Heat Capacity

Water has a high capacity meaning it can be heated relatively difficultly.

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Hydrophilic

Water is hydrophilic, like molecules being able to get dissolved in water.

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Hydrophobic

Molecules as fats, oils and other lipids being not water-soluble are called hydrophobic.

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Hydration Shell

Water molecules form layers around the ions thus building a so-called hydration shell.

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Osmosis

Water can passively move through semi-permeable membranes.

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Surface Tension

Surface tension: water molecules at the surface are more attached to each other

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High Heat Capacity

The many hydrogen bonds that link water molecules let water absorb a large amount of heat.

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Stable Temperature

Because the temperature of water rises and falls slowly, living organisms can maintain their normal temperature.

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Density Changes

Density based on temperature where water contract when they freeze.

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insulator

Because expansion causes ice to have a lower density than liquid water and therefor ice floats on liquid water it acts as protection

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% of water on earth and in body

Around 70% % of the planet is covered by water, same coverage for water in the human body

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Solvent

Acting as a universal Solvent to dissolve in it is related to the Polarity

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Hydrogen Bonding

The hydrogen bonding provide chemical reaction to occur in organisms.

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adhesion

The ability to cling to other is called Adhesion

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molecule

The ability for water molecule water molecules with some very unique.

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Water Dissociation

When water dissociates, it breaks apart into hydrogen ions (H+) and hydroxide ions (OH-).

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Classifying a Substance

Classifying a substance based on the hydrogen ion concentration versus hydroxide ions.

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pH Scale

A measure of how acidic or basic a substance is.

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pH 7 substance

A substance with a pH of 7, like water, releases an equal concentration of hydrogen ions and hydroxide ions.

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Substance with pH > 7

A substance with a pH greater than 7, it is a base and releases more hydroxide ions.

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Acidic substance

Acids taste sour and release more hydrogen ions when its pH is acidic.

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Aqueous solutions

Aqueous solutions that may be acidic, alkaline, or neutral according to the H+ and OH- concentration of the solution.

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pH acidic

A solution is more acidic when the pH decreases, and will be between 1 and 7.

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Neutral Solution

Solutions containing equal numbers of H+ and OH- ions have neutral pH (7.0) and are neither acidic, nor alkaline.

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Alkaline Solutions

Solutions between pH 7 and 14 have more OH- than H+, and are referred to as alkaline (basic) solutions.

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Study Notes

Chemical Bonds and Functional Groups, Water, pH

  • Chemical compounds consist of two or more atoms joined together.
  • A stable compound forms when the energy level of the joined compound is less than that of the separate atoms.
  • Chemical properties of compounds are determined by the atomic number of the participants, which also indicates the type of chemical bond formed.

Covalent Bond

  • Atoms share electrons in a covalent bond, forming binding electrons. Shared electrons allow participants to complete their outermost electron shells to reach a noble gas configuration.
  • Besides bonding electrons, atoms may possess lone pair or non-bonding electrons. These do not participate directly in covalent bond formation.
  • The first covalent bond formed between two atoms is called a sigma (σ) bond.
  • Further covalent bonds that can form are called pi (Ï€) bonds.
  • Bonds can be double (σ+Ï€1 ) or triple (σ+Ï€1+Ï€2 ).
  • Covalent bonds tend to be strong, high energy, and primary bonds, needing energy to disrupt.
  • In non-polarized covalent bonds, electrons are shared equally around the two participant atoms' nuclei. When electrons spend more time around one participant's nucleus, the bond is called a polar covalent bond.

Ionic Bond

  • An ionic bond forms between atoms tending to create oppositely charged ions.
  • Elements in the 1st and 2nd groups tend to lose one or two electrons, allowing them to achieve a noble gas configuration.
  • For example, sodium loses an electron to chlorine; both become ionized and attain a noble gas configuration.
  • Table salt features a crystal structure made of oppositely charged sodium and chlorine ions.

Metallic Bond

  • Metallic bonding occurs in metals.
  • Electrons are shared and occupy an electron orbital which encompasses all of the metal atoms present.
  • These delocalized electrons give metals good heat and electrical conductivity.

Secondary bonds

  • Secondary bonds are weaker than primary bonds.
  • They can drastically alter the structure and function of molecules in living systems.

Hydrogen Bond

  • Hydrogen bond is a chemical bond, which may occur between hydrogen and N, O, or F.
  • Hydrogen becomes partially positive charged due to its atomic nucleus.
  • The electrons will spend relatively shorter time around hydrogen's single proton than around the other participant’s nucleus.
  • Electrons spend relatively more time around these atomic nuclei F, O, or N, becoming slightly negative in molecules.
  • The non-binding electrons of the atom with high electronegativity become partially shared with the hydrogen.
  • Hydrogen bonds stabilize the secondary structure of proteins, enable base pairing in nucleic acids, and allow water to be a fluid on Earth.

Other Bonds

  • Dipole-dipole bonds occur between dipoles molecules.
  • London (van der Waals) forces

Chemical Groups

  • Chemical groups determine the chemical and physical properties of molecules, also determining reaction occurrence.
  • Functional groups include:
    • Hydroxyl (-OH): increases water solubility
    • Carbonyl (-CHO or -CO): If located at the end of the carbon-backbone chain, the molecule ends with "-hyde". If attached to a carbon atom inside the chain, it is called a "keto group" and the backbone ends with "-one".
    • Carboxyl (-COOH): promotes dissociation in solutions and acts as an acid
    • Amino (-NH2): acts as a base in organic molecules; decreases the hydrogen concentration

Water

  • The present life on Earth relies on water, due to its unique molecular structure.
  • A water molecule has a V-shape because of non-bonding electron pairs on the oxygen atom.
  • Oxygen's higher electron affinity pulls electrons in the covalent bonds closer, creating a dipole property.
  • Water molecules can form up to four hydrogen bonds with surrounding water molecules.
  • Water exists in all three states (solid, liquid, gas) on Earth, depending on air pressure and temperature.
  • Below 0°C, the movement of water slows; hydrogen bonds organize, and water freezes, causing it to expand and decrease in density.
  • When heated to 100°C, water boils into gas phase. Water molecules dissociate into -OH- and H+, maintaining a neutral pH.
  • Water has a high heat-capacity due to hydrogen bonds.
  • Water has diverse biological roles ensuring cohesive behavior due to hydrogen-bonds.
  • Water stabilizes body temperature, releases heat gradually, and prevents overheating because it can be heated relatively hard.
  • It also insulates lower water layers, preventing animals and plants from freezing.
  • Molecules may dissolve in aqueous solutions are hydrophilic; water is hydrophilic (=water-loving). Molecules such as lipids, oils, and fats not being water-soluble are hydrophobic (=phobic-to hate).
  • Lipophilic compounds are hydrophobic, they can dissolve in lipids.
  • Water molecules form a hydration shell around ions, facilitating their dissolving.
  • Water's low viscosity allows blood and body fluids to move easily in the human body.
  • Water can be a participant or product in condensation (dehydration) or hydrolysis (hydration) chemical reactions. It also moves through semi-permeable membranes via osmosis.
  • Water has a vital role in photosynthesis; water is practically the photolysis of water.
  • Water has positive and negative poles.

Properties Of Water

  • Water has a high surface tension: water molecules are more strongly attached at the surface than to the air above.
  • Water molecules cling tightly to each other due to attachment.
  • High heat capacity: many hydrogen bonds allow water to absorb large amounts of heat without changing its state, protecting living things from temperature changes.
  • Unlike other compounds, water expands when it freezes due to hydrogen bonds forming a crystal structure.
  • Water is a universal solvent for a lot of substances, because of it's polarity
  • Water exhibits cohesion: hydrogen bonds stick water molecules together, allowing for chemical reactions in organisms and adhesion: the ability to cling to other organic surfaces.

Water in the World

  • Over 70% of planet is covered by water.
  • Our body consists of approximately 70% water.
  • The structure of a water molecule and its capacity to form hydrogen bonds makes it unique.

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Description

This section discusses chemical compounds, focusing on how atoms join to form stable compounds with lower energy levels. It explores covalent bonds, where atoms share electrons to achieve a noble gas configuration, and differentiates between sigma and pi bonds. The role of bonding and non-bonding electrons in determining chemical properties is also highlighted.

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