BIOL lecture 3 second part

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Questions and Answers

What property of water allows it to effectively regulate the Earth’s climate?

Low specific heat

High density

Low thermal conductivity

High heat of vaporization (correct)

How does water serve as an insulator for the human body?

By evaporating quickly

By absorbing heat quickly

By retaining heat before increasing in temperature (correct)

By freezing at low temperatures

What effect does evaporation have on the temperature of the remaining liquid water?

It has no effect

It doubles the temperature

It increases the temperature

It decreases the temperature (correct)

Why do large bodies of water, like oceans, have a nearly uniform vertical temperature profile?

Because of their high thermal conductivity Signup and view all the answers

What is the term for substances that can dissolve in water?

Solutes Signup and view all the answers

What effect does sweating have on body temperature?

It decreases body temperature through evaporative cooling Signup and view all the answers

What is the primary reason for water's ability to act as a coolant?

Its high heat of vaporization Signup and view all the answers

What type of substances can interact favorably with water due to its polar nature?

Polar solutes Signup and view all the answers

Which of the following statements correctly describes a strong acid?

It completely dissociates into ions in solution Signup and view all the answers

What is the result of neutralizing an acid with a base?

Water and salt Signup and view all the answers

Which of the following acids is considered a weak acid?

HCOOH Signup and view all the answers

How would you classify sodium hydroxide (NaOH) in terms of acid-base chemistry?

Strong base Signup and view all the answers

What happens to litmus paper when it is exposed to a basic solution?

It turns blue Signup and view all the answers

Which of the following is a characteristic property of acids?

Taste sour Signup and view all the answers

Which equation represents the dissociation of a strong acid?

HCl → H+ + Cl⁻ Signup and view all the answers

When mixing acetic acid (CH3COOH) with sodium hydroxide (NaOH), which of the following occurs?

Water and salt are produced Signup and view all the answers

Which of the following is not a strong base?

HCl Signup and view all the answers

What is a characteristic property of strong bases in aqueous solutions?

They are slippery and soapy. Signup and view all the answers

What should be done first when diluting concentrated acids?

Add acid to water. Signup and view all the answers

What is the main reason water is preferred for the dilution of concentrated acids?

Water can absorb heat safely. Signup and view all the answers

Buffers can resist changes in pH due to the presence of which compounds?

Weak acids and their conjugate bases. Signup and view all the answers

What type of buffer consists of a weak base and the acid formed from it?

Basic buffer. Signup and view all the answers

Chemical burns from strong bases are primarily caused by what property?

Their ability to deprotonate weak acids. Signup and view all the answers

What happens when water is added to concentrated acid?

It can cause the acid to fume or boil. Signup and view all the answers

What term is used to describe substances that do not dissolve well in water?

Hydrophobic Signup and view all the answers

Which of the following substances is considered hydrophilic?

Salts Signup and view all the answers

What is the pH of pure water?

7 Signup and view all the answers

How does the pH of a solution change when an acidic substance is dissolved in water?

It becomes more acidic Signup and view all the answers

What is the relationship between hydrogen ions and the pH scale?

A higher concentration of hydrogen ions results in a lower pH Signup and view all the answers

What happens to the pH of water when substances are dissolved in it?

It changes based on the substances dissolved Signup and view all the answers

Which equation represents the formula for calculating pH?

pH = -log [H+] Signup and view all the answers

What ions are produced when water molecules dissociate?

Hydrogen (H+) and Hydroxyl (OH-) Signup and view all the answers

What is the primary purpose of buffer solutions in chemical applications?

To maintain a constant pH level Signup and view all the answers

Which buffer is appropriate for a pH range of 6.1-7.5?

PIPES Signup and view all the answers

What pH range do most cells in the human body operate within?

7.2 to 7.6 Signup and view all the answers

What are the consequences of pH deviation in biological systems?

Denaturation of proteins and potential cell death Signup and view all the answers

Which component of the carbonate/carbonic acid system acts as a weak acid?

Carbonic acid (H2CO3) Signup and view all the answers

How does lactic acid affect the pH balance in the blood during exercise?

It donates protons, leading to increased acidity. Signup and view all the answers

What is the pH environment within lysosomes, and how does it aid their function?

pH 5; enables the digestion of molecules Signup and view all the answers

Which buffer would be most suitable to maintain a pH of 8?

Tris-HCl Signup and view all the answers

Study Notes

High Heat of Vaporization

Water regulates Earth's climate by absorbing solar heat in oceans, which is released during evaporation.
Warm tropical air carries water vapor; condensation releases heat, stabilizing temperatures in ecosystems.
Water has the highest thermal conductivity among liquids, ensuring uniform temperature in lakes and oceans.

Temperature Regulation

Water remains liquid within a temperature range of 0 - 100° C, facilitating life on Earth.
Acts as an insulator, retaining body temperature in cold conditions, while also functioning as a coolant through processes like sweating.

Evaporative Cooling

Increased temperature raises kinetic energy of water molecules, leading to evaporation.
Evaporation lowers the average kinetic energy of the remaining liquid, resulting in a temperature drop.

Water as a Solvent

Water, a universal solvent, effectively dissolves polar solutes due to its polarity.
Hydrophilic (water-loving) substances such as acids, alcohols, and salts dissolve well in water.
Hydrophobic (water-repelling) substances like lipids do not dissolve in water.

pH of Water

Pure water has a neutral pH of 7 and does not act as an acid or base; it changes pH when substances dissolve in it.
Natural rainwater has a slightly acidic pH of 5.6 due to dissolved carbon dioxide and sulfur dioxide.

Acids, Bases, and Buffers

Organisms are sensitive to pH changes: acids lower pH (<7), while bases increase it (>7).
pH measures hydrogen ion concentration, defined mathematically as pH = -log [H+].
Water disassociates into hydroxyl (OH-) and hydrogen (H+) ions, maintaining [H+] = [OH-] in pure water.

Characteristics of Acids and Bases

Acids donate protons (H+), taste sour, change litmus paper red, and are corrosive.
Bases accept protons (H+), feel slippery, change litmus paper blue, and can neutralize acids.
Strong acids and bases fully dissociate in water, while weak acids and bases partially dissociate.

Neutralization Reactions

Occurs when an acid and base react to form water and a salt: H+(aq) + OH-(aq) → H2O.

Properties of Strong Acids and Bases

Strong acids (e.g., HCl, H2SO4) and bases (e.g., NaOH, KOH) fully dissociate in solution, resulting in strong proton acceptors or donors.

Dilution of Acids

When diluting concentrated acids, always add acid to water to avoid hazardous reactions; heat is generated by acid-water interactions.

Buffers

Buffers resist pH changes with the addition of acids or bases and are crucial for maintaining stable pH in biological systems.
Common buffers include MES, PIPES, HEPES, and Tris-HCl, with specific pH ranges for effective use.

Buffer Systems in Biology

Biological systems typically operate within a narrow pH range (7.2 - 7.6) to prevent protein denaturation and cell dysfunction.
The carbonate/bicarbonate buffering system in blood helps regulate pH, particularly during metabolic processes such as lactic acid production.

Lysosomal Environment

Animal cells contain lysosomes, pouches with acidic interiors (pH 5) for recycling molecules with enzymes that require low pH for activity.

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Description

Explore the significance of water's high heat of vaporization and its role in regulating Earth's climate. This quiz examines how water absorbs and dissipates heat, influences temperature in aquatic ecosystems, and supports movement of warm air. Understand why water is essential for maintaining stable environments.