Water Properties and Molecular Structure
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Questions and Answers

What type of electrical charge does the oxygen atom carry in a water molecule?

  • No charge
  • Fully negative
  • Partially positive δ+
  • Partially negative δ- (correct)

What property of water is a result of the polarity of water molecules?

  • High boiling point (correct)
  • High viscosity
  • Low density
  • Lack of attraction between molecules

What term describes the phenomenon where water molecules are attracted to one another due to their polarity?

  • Adhesion
  • Diffusion
  • Hydrophobic interactions
  • Cohesion (correct)

Which characteristic of hydrogen bonds is true?

<p>They are weak and transitory. (D)</p> Signup and view all the answers

Which statement regarding the partial charges in a water molecule is accurate?

<p>The hydrogen atoms are partially positive. (C)</p> Signup and view all the answers

What term describes molecules that are attracted to water?

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

What happens to hydrophobic molecules in water?

<p>They aggregate or assume specific shapes. (B)</p> Signup and view all the answers

In pure water, what is the relationship between hydrogen and hydroxide ions?

<p>They are equal in concentration. (D)</p> Signup and view all the answers

What role does water play in relation to polar molecules and ions?

<p>It dissolves them. (A)</p> Signup and view all the answers

What is the dissociation reaction of water?

<p>H-O-H → H^{+} + OH^{-} (B)</p> Signup and view all the answers

What is cohesion in relation to water molecules?

<p>Water molecules stick to other water molecules. (B)</p> Signup and view all the answers

What is the significance of water's high specific heat?

<p>It requires a large amount of energy to change its temperature. (B)</p> Signup and view all the answers

How does water exhibit adhesion?

<p>Water molecules bond with other polar molecules. (C)</p> Signup and view all the answers

Why is solid water less dense than liquid water?

<p>The molecular structure causes water to expand when frozen. (D)</p> Signup and view all the answers

What does it mean when we say that bodies of water freeze from the top down?

<p>The top layer freezes first, insulating the water below. (A)</p> Signup and view all the answers

Which pH value is typically associated with pure water?

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

What is the definition of an acid in aqueous solution?

<p>A substance that releases H⁺ in water (D)</p> Signup and view all the answers

What effect do buffers have on pH when an acid is added?

<p>They keep the pH relatively constant. (B)</p> Signup and view all the answers

Which of the following is an example of a base?

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

In a basic solution, the concentration of H⁺ compared to OH⁻ is characterized by which relationship?

<p>[H⁺] &lt; [OH⁻] (A)</p> Signup and view all the answers

Which of the following pH values represents a basic solution?

<p>8 (A), 14 (B)</p> Signup and view all the answers

Which of the following compounds dissociates to produce H⁺ ions in solution?

<p>Hydrochloric acid (HCl) (B)</p> Signup and view all the answers

What happens to proteins when the pH is too high or too low?

<p>They become denatured. (C)</p> Signup and view all the answers

Which example is associated with an acidic solution?

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

What type of solution would lemon juice be classified as?

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

What can happen if there is too much or too little H+ in a biological system?

<p>Denaturation of proteins (A)</p> Signup and view all the answers

What is the normal blood pH range that must be maintained in organisms?

<p>7.35 - 7.45 (A)</p> Signup and view all the answers

What is the role of bicarbonate ion in the buffering system?

<p>It maintains the pH by neutralizing acids (D)</p> Signup and view all the answers

Which reaction correctly represents the carbonic acid-bicarbonate buffering system?

<p>H₂O + CO₂ ⇌ H₂CO₃ ⇌ HCO₃⁻ + H⁺ (A)</p> Signup and view all the answers

What might result from the pH levels falling outside the range of 7.35 - 7.45?

<p>Altered protein function (D)</p> Signup and view all the answers

Flashcards

Polarity of water molecule

Uneven distribution of charge within a water molecule.

Electro-negativity of Oxygen

Oxygen attracts electrons more strongly than hydrogen in a water molecule.

Partial charges in water

Oxygen becomes slightly negative (δ-) and hydrogen slightly positive (δ+).

Hydrogen bond in water

Weak attraction between a hydrogen atom and an electronegative atom (like oxygen).

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Cohesion in Water

Water molecules stick to each other due to hydrogen bonds.

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What is an acid?

An ionic molecule that releases H⁺ (hydrogen ions) when dissolved in water.

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What is a base?

An ionic molecule that removes H⁺ (hydrogen ions) when dissolved in water.

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Acidic solution

A solution where the concentration of H⁺ ions is higher than OH⁻ ions.

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Basic solution

A solution where the concentration of OH⁻ ions is higher than H⁺ ions.

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HCl dissociation

Hydrochloric acid (HCl) dissociates in water to form H⁺ ions and Cl⁻ ions.

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Adhesion

Water molecules stick to other polar molecules due to hydrogen bonding.

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High specific heat

Water requires a lot of energy to change its temperature.

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High heat of vaporization

Water requires lots of energy to evaporate.

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Solid water less dense than liquid

Ice floats because it's less dense than liquid water.

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Bodies of water freeze from the top down

Ice forms at the surface of a body of water and insulates the water below.

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Water is a good solvent

Water can dissolve many substances, like sugars, salts, and some gases. This is because of the polar nature of water molecules, which can interact with and pull apart the molecules of the substance being dissolved.

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Hydrophilic

Substances that attract water molecules and are easily dissolved in water. These substances typically have polar molecules or ions.

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Hydrophobic

Substances that repel water and don't dissolve in water. These substances typically have nonpolar molecules.

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Water's effect on nonpolar molecules

Water can cause nonpolar molecules to clump together or form specific shapes. This is because the water molecules try to minimize contact with the hydrophobic substances.

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pH of pure water

Pure water is neutral because it has equal amounts of hydrogen ions ($H^{+}$) and hydroxide ions ($OH^{-}$).

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pH Scale

A measure of the acidity or alkalinity of a solution. It ranges from 0 to 14, with 0 being the most acidic and 14 being the most basic. A pH of 7 is neutral.

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Acidic

Solutions with a pH below 7. They have a high concentration of hydrogen ions (H+).

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Basic (Alkaline)

Solutions with a pH above 7. They have a low concentration of hydrogen ions (H+).

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Buffer

A substance that resists changes in pH. It can either release or absorb hydrogen ions (H+) to maintain a relatively constant pH.

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Biological Buffers

Buffers that are essential for maintaining the correct pH within living organisms. Proteins are sensitive to pH changes, and buffers help keep them stable.

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pH in Organisms

The measure of acidity or alkalinity in living things, which must remain within a very narrow range to prevent damage to proteins.

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Protein Denaturation

When a protein loses its shape and function due to extreme changes in pH or temperature.

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Blood pH

The pH of blood, which must stay within a very specific range (7.35-7.45).

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What does the bicarbonate buffer system do?

It's a system in the blood that helps maintain a stable pH by reacting with excess acids or bases.

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Why is buffer system important?

It prevents extreme shifts in pH, protecting vital proteins and keeping the body functioning properly.

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