Properties of Water and Life
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Questions and Answers

What is the primary reason that water is essential for all living organisms?

  • It is the most abundant substance on Earth.
  • It is the biological medium on Earth. (correct)
  • It moderates temperature effectively.
  • It forms hydrogen bonds with gases.

    • How are water molecules described in terms of their charge?

  • They have a neutral charge.
  • They are positively charged at both ends.
  • They are polar with opposite charges at each end. (correct)
  • They are nonpolar and evenly charged.

    • Which of the following is NOT one of the four emergent properties of water that aid life on Earth?

  • Expansion upon freezing
  • Cohesive behavior
  • Thermal conductivity (correct)
  • Versatility as a solvent

    • What role does cohesion play in plants?

    <p>It aids in the transport of water against gravity.</p> Signup and view all the answers

    Which statement best describes adhesion in the context of water?

    <p>It is the attraction between water and different substances.</p> Signup and view all the answers

    What does surface tension measure in a liquid such as water?

    <p>The strength of the hydrogen bonds in the liquid.</p> Signup and view all the answers

    How does water's ability to expand upon freezing contribute to its importance for life?

    <p>It allows aquatic life to survive under frozen surfaces.</p> Signup and view all the answers

    What is the primary impact of water's versatility as a solvent?

    <p>It aids in biochemical reactions and nutrient transport.</p> Signup and view all the answers

    What is a calorie defined as in terms of water temperature change?

    <p>The amount of heat required to raise the temperature of 1 g of water by 1°C</p> Signup and view all the answers

    Why does water have a high specific heat?

    <p>Because of hydrogen bonding in water molecules</p> Signup and view all the answers

    What is the significance of water's high specific heat for life on Earth?

    <p>It provides resistance against rapid temperature changes</p> Signup and view all the answers

    What process cools the remaining surface of a liquid as it evaporates?

    <p>Evaporative cooling</p> Signup and view all the answers

    Why does ice float on water?

    <p>Because hydrogen bonds in ice are more ordered, making it less dense</p> Signup and view all the answers

    Which of the following best describes a solvent?

    <p>The dissolving agent in a solution</p> Signup and view all the answers

    What happens when an ionic compound dissolves in water?

    <p>It forms a hydration shell around each ion</p> Signup and view all the answers

    How does water act as a versatile solvent?

    <p>Because of its polarity allowing hydrogen bond formation</p> Signup and view all the answers

    At what temperature does water reach its maximum density?

    <p>4°C</p> Signup and view all the answers

    What effect does evaporative cooling have on organisms?

    <p>It minimizes variability in body temperatures</p> Signup and view all the answers

    What defines a hydrophilic substance?

    <p>It has an affinity for water.</p> Signup and view all the answers

    What is a characteristic of hydrophobic substances?

    <p>They do not have an affinity for water.</p> Signup and view all the answers

    What happens to the concentrations of H+ and OH– in pure water?

    <p>They are equal.</p> Signup and view all the answers

    What is the pH of a neutral aqueous solution?

    <p>7</p> Signup and view all the answers

    What occurs when an acid is added to a solution?

    <p>The H+ concentration increases.</p> Signup and view all the answers

    What is the role of buffers in biological systems?

    <p>They minimize changes in H+ and OH– concentrations.</p> Signup and view all the answers

    Which of the following best defines an acid?

    <p>A substance that increases H+ concentration.</p> Signup and view all the answers

    What is considered a stable suspension of fine particles in a liquid?

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

    What environmental effect can acid precipitation have?

    <p>Alter soil chemistry negatively.</p> Signup and view all the answers

    How does burning fossil fuels affect ocean chemistry?

    <p>It contributes to ocean acidification.</p> Signup and view all the answers

    What is the general pH range for most biological fluids?

    <p>6 to 8</p> Signup and view all the answers

    What is the effect of hydronium ions (H3O+) in solution?

    <p>They increase the concentration of H+ ions.</p> Signup and view all the answers

    What occurs in a solution when the pH value is less than 7?

    <p>The solution is acidic.</p> Signup and view all the answers

    Study Notes

    The Importance of Water

    • Water is the biological medium on Earth, all living organisms need water.
    • Cells are typically 70–95% water.
    • The abundance of water is the main reason the Earth is habitable.

    The Structure of Water

    • Water is a polar molecule due to the uneven sharing of electrons between hydrogen and oxygen.
    • The opposite ends of a water molecule have opposite charges.
    • This polarity allows water molecules to form hydrogen bonds with each other.

    Properties of Water

    • Water's properties are responsible for creating an environment suitable for life.

    Cohesion

    • Hydrogen bonds hold water molecules together, this is cohesion.
    • Cohesion helps water transport against gravity in plants.
    • Adhesion is the attraction between different substances like water and plant cell walls.
    • Surface Tension: This is the force needed to break the surface of a liquid and it’s related to cohesion.

    Temperature Moderation

    • Water has a high specific heat, meaning it absorbs or releases large amounts of heat with little change in its own temperature.
    • The high specific heat of water minimizes temperature fluctuations to within limits that permit life.
    • Heat is absorbed when hydrogen bonds break and released when they form.

    Evaporative Cooling

    • Evaporation is the transformation of a liquid to a gas.
    • Heat of vaporization: the heat required to convert 1 g of a liquid into gas.
    • As a liquid evaporates, its remaining surface cools, called evaporative cooling.

    Insulation of Bodies of Water

    • Ice floats because of its ordered hydrogen bonds, making it less dense.
    • Water reaches its greatest density at 4°C.

    Water as a Solvent

    • A solution is a homogenous mixture of substances.
    • Solvent: the dissolving agent.
    • Solute: the substance that is dissolved.
    • Aqueous solutions are those with water as the solvent.
    • Water is a versatile solvent because of its polarity.
    • Ionic compounds dissolve in water forming hydration shells around each ion.
    • Hydrophilic substances have an affinity for water.
    • Hydrophobic substances do not have an affinity for water.
    • A colloid is a stable suspension of particles in a liquid.

    Solute Concentration in Aqueous Solutions

    • Most biochemical reactions occur in aqueous solutions.
    • The concentration of solutes affects the rate of chemical reactions.

    Acids, Bases, and pH

    • The dissociation of water molecules produces hydrogen ions (H+) and hydroxide ions (OH–).
    • The concentration of H+ and OH– affects the chemistry of cells.
    • The pH scale measures the acidity or basicity of a solution.
    • Acidic solutions have a pH less than 7, basic solutions have a pH greater than 7.
    • Most biological fluids have a pH between 6 and 8.
    • Buffers minimize changes in H+ and OH– concentrations in a solution.

    Threats to Water Quality

    • Acid precipitation: Rain, snow, or fog with a pH lower than 5.6.
    • Acid precipitation is caused by pollutants mixing with water in the air.
    • CO2 from fossil fuel combustion causes:
      • The “greenhouse” effect causing global warming.
      • Ocean acidification which affects coral reefs.

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    Description

    Explore the fundamental properties of water, including its biological importance, structure, and unique characteristics. This quiz covers cohesion, adhesion, and temperature moderation, highlighting how these properties support life on Earth. Understanding these concepts is crucial for appreciating the role of water in ecosystems and biology.

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