Unique Properties and Importance of Water
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Questions and Answers

What percentage of Earth's surface is covered by water?

  • 75% (correct)
  • 50%
  • 25%
  • 90%

    • Water only exists on Earth in its liquid state.

    False

    What molecule is water composed of?

    Two hydrogen atoms and one oxygen atom.

    Water is commonly referred to as the biological __________ of life.

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

    What unique property of water allows it to support life?

    <p>Surface tension</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Adhesion = Attraction between molecules of different substances Cohesion = Attraction between molecules of the same substance Solvent = Substance that dissolves a solute pH = Measure of acidity or alkalinity of a solution</p> Signup and view all the answers

    Which of the following statements about water is true?

    <p>Water exists in a solid, liquid, and gas form on Earth.</p> Signup and view all the answers

    Approximately _____ percent of Earth's water is stored underground.

    <p>2</p> Signup and view all the answers

    What is the pH range of a base?

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

    Bases and acids can harm organisms and cause damage to materials.

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

    What is formed when an acid and a base react together?

    <p>Water and a salt</p> Signup and view all the answers

    A solution with a pH of 7 is considered _____ neutral.

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

    Match the following acids and bases with their properties:

    <p>Baking soda = A base with a bitter taste Lye = A strong base that can burn skin Hydrochloric acid = A strong acid that can damage glass Bleach = A strong base that removes color</p> Signup and view all the answers

    What is the chemical equation for the neutralization reaction between sodium hydroxide and hydrochloric acid?

    <p>NaOH + HCl → NaCl + H2O</p> Signup and view all the answers

    Water is considered the universal solvent because it can dissolve most substances.

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

    Water's high surface tension is caused by extensive _____ bonding.

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

    Only 3 percent of the water on Earth is freshwater.

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

    Name one way water is recycled in nature.

    <p>Evaporation, condensation, precipitation, sublimation, or transpiration.</p> Signup and view all the answers

    Water is often referred to as the __________ solvent.

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

    Match the following processes of the water cycle with their descriptions:

    <p>Evaporation = Changes liquid water to vapor Condensation = Forms clouds from vapor Precipitation = Falls back to Earth as rain or snow Transpiration = Plants release water vapor</p> Signup and view all the answers

    What is the chemical formula for water?

    <p>H2O</p> Signup and view all the answers

    The oxygen atom in a water molecule has a partial positive charge.

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

    What type of bond forms between water molecules?

    <p>Hydrogen bond</p> Signup and view all the answers

    The percentage of freshwater that is found frozen in glaciers is approximately __________.

    <p>97</p> Signup and view all the answers

    Which property allows water to interact with many other molecules?

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

    The blue hue of large bodies of water is due to the reflection of the sky.

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

    During which process does water vapor change to liquid water droplets?

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

    Water's unique properties are mainly due to its __________ structure.

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

    Match the following water properties with their definitions:

    <p>Polarity = Unequal distribution of charge Solubility = Ability to dissolve substances Transparency = Allows light to pass through Density = Mass per unit volume</p> Signup and view all the answers

    What is the purpose of cellular respiration?

    <p>To transfer energy from glucose to ATP</p> Signup and view all the answers

    An increase in hydrogen ion concentration results in a lower pH.

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

    What is a buffer?

    <p>A substance that moderates changes in pH.</p> Signup and view all the answers

    The chemical formula for glucose is ______.

    <p>C6H12O6</p> Signup and view all the answers

    Match the following substances with their classifications:

    <p>HCl = Acid NaOH = Base Distilled Water = Neutral Lemon Juice = Acid</p> Signup and view all the answers

    Which pH value represents a neutral solution?

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

    Water is considered a strong buffer.

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

    What happens to the pH of a solution if a strong acid is added?

    <p>The pH decreases.</p> Signup and view all the answers

    The pH scale ranges from ______ to ______.

    <p>0, 14</p> Signup and view all the answers

    What do bases do in a solution?

    <p>Absorb H+ ions</p> Signup and view all the answers

    A solution with a pH of 5 is more acidic than a solution with a pH of 7.

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

    What is the primary effect of hydronium ions on pH?

    <p>They lower the pH.</p> Signup and view all the answers

    Stronger acids can harm organisms if the protective layer of ______ is breached.

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

    Match the following pH values with their classification:

    <p>pH 3 = Strong Acid pH 7 = Neutral pH 11 = Weak Base pH 14 = Strong Base</p> Signup and view all the answers

    What property of water allows it to absorb or release large amounts of heat with only slight temperature changes?

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

    The boiling point of water is 0°C.

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

    What is the specific heat capacity of water?

    <p>1 cal/(g°C)</p> Signup and view all the answers

    Water is most dense at __________ °C.

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

    Match the following temperatures with their associated state changes:

    <p>0°C = Freezing point of water 100°C = Boiling point of water 4°C = Most dense state of water 32°F = Freezing point of water in Fahrenheit</p> Signup and view all the answers

    Which of the following statements about hydrogen bonds in water is correct?

    <p>Hydrogen bonds break and reform during the temperature changes of water.</p> Signup and view all the answers

    Ice floats on liquid water because it has a higher density.

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

    What is the primary reason polar solvents are effective in dissolving polar solutes?

    <p>Both solute and solvent have similar polarity.</p> Signup and view all the answers

    What process do water molecules undergo to change from liquid to gas?

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

    Surface tension is solely due to the presence of nonpolar substances in water.

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

    Water’s ability to dissolve most biologically significant compounds makes it a vital __________ inside organisms.

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

    What ions are formed when pure water dissociates?

    <p>Hydronium ion (H3O+) and hydroxide ion (OH-)</p> Signup and view all the answers

    Match the following processes with their roles in metabolism:

    <p>Anabolic reactions = Build up molecules and store energy Catabolic reactions = Break down molecules and release energy Photosynthesis = Convert sunlight energy to glucose Cellular respiration = Convert glucose to usable energy</p> Signup and view all the answers

    Cohesion in water molecules occurs due to __________ bonds.

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

    Why is water essential for life processes?

    <p>It participates in nearly all chemical reactions necessary for life.</p> Signup and view all the answers

    Match the water properties with their definitions:

    <p>Cohesion = Attraction between molecules of the same kind Adhesion = Bonding of water molecules to another substance Surface Tension = Resistance of a liquid's surface to rupture Capillary Action = Ability to flow against gravity in narrow spaces</p> Signup and view all the answers

    Human beings can survive a few weeks without water.

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

    What phenomenon allows water to rise in a straw?

    <p>Capillary action</p> Signup and view all the answers

    What is the primary state of most water on Earth?

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

    Hydrogen bonds in water molecules are permanent and do not change.

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

    The temperature at which water transitions from a solid to a liquid is called the __________.

    <p>melting point</p> Signup and view all the answers

    What is surface tension?

    <p>The tendency of a liquid’s surface to resist rupture.</p> Signup and view all the answers

    In the equation 2 H2O → H3O+ + OH-, the H3O+ ion is formed when a water molecule __________ a hydrogen ion.

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

    Which of the following is NOT a property of water?

    <p>Excellent conductor of electricity</p> Signup and view all the answers

    Water's ability to form drops is due to its adhesion property.

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

    What role does capillary action play in plants?

    <p>It helps move water upward from the roots to the leaves.</p> Signup and view all the answers

    Adhesion refers to the bonding of water molecules to __________.

    <p>another substance</p> Signup and view all the answers

    Match examples to the correct property of water:

    <p>Cohesion = Water droplets on a waxed car Surface Tension = Water striders walking on water Capillary Action = Water rising in a straw Adhesion = Water adhering to a glass surface</p> Signup and view all the answers

    Study Notes

    Unique Properties of Water

    • Water is essential for all known life forms, comprising a significant portion of organisms.
    • Water is a simple molecule (H₂O), yet its structure leads to unique properties crucial for life.
    • Earth is often called the "water planet" as almost 75% of its surface is covered by water.
    • Water exists in three states: liquid, solid (ice), and gas (water vapor).

    Distribution of Earth's Water

    • Approximately 97% of Earth's surface water is saltwater found primarily in oceans.
    • Only about 3% of Earth's water is freshwater, mostly frozen in glaciers and polar ice caps.
    • A small amount of freshwater exists in underground spaces, the air, and living organisms.
    • Surface water covers about 72% of Earth's surface.

    Water Cycle

    • Water constantly cycles through living and non-living parts of the biosphere.
    • Key processes in the water cycle include evaporation, sublimation, transpiration, condensation, and precipitation.

    Water's Importance to Life

    • Water's polarity and structure allow it to interact with other molecules necessary for life.
    • Most cellular substances are suspended in a water-based cytoplasmic environment.
    • Water's properties, including polarity, solubility, and cohesion, make it a vital solvent in organisms. Life couldn't exist without water.

    Structure and Properties of Water

    • Water is a polar molecule due to oxygen's higher electronegativity, creating partial negative charges on oxygen and partial positive charges on hydrogen atoms.
    • This polarity enables hydrogen bonding, crucial weak interactions among water molecules.
    • Water is transparent in small quantities but appears light blue in larger bodies due to light absorption and scattering.
    • The transparency allows sunlight penetration, supporting photosynthesis in aquatic organisms.

    Solvency

    • Water is a prominent ingredient in solutions, acting as a solvent for numerous substances.
    • A solution is a homogeneous mixture of a solute (dissolved substance) and a solvent (substance in which the solute dissolves).
    • Water's polarity makes it a universal solvent, dissolving many polar substances. However, it doesn't dissolve nonpolar substances like oil.

    Cohesion

    • Cohesion describes the attraction of water molecules to each other due to the hydrogen bonds.
    • Water forms droplets due to cohesive forces—molecules stick together.

    Surface Tension

    • Surface tension is a liquid's resistance to rupture, due to the stronger intermolecular forces at the surface.
    • Water's strong surface tension is due to extensive hydrogen bonding at the water-air interface.

    Adhesion

    • Adhesion is the attraction of water molecules to other substances, like glass.
    • Hydrogen bonds readily break and re-form, allowing water to adhere to surfaces.

    Capillary Action

    • Capillary action enables liquids to move against gravity through narrow spaces due to adhesion and surface tension.
    • Water's adhesion to surfaces and surface tension pulls water upward, defying gravity.

    Temperature Moderation

    • Water has a high heat capacity, absorbing and releasing a large amount of heat with minimal temperature change.
    • This is due to the breaking and reforming of hydrogen bonds.
    • Water's high specific heat capacity (1 cal/(g°C)) makes it crucial for temperature regulation in living systems.
    • Sweating is an example of water's high heat capacity—evaporation cools the body.

    Freezing and Boiling Points

    • Water freezes at 0°C (32°F) and boils at 100°C (212°F) due to hydrogen bonds.
    • Ice (solid water) has lower density than liquid water because of hydrogen bonds causing molecules to be spaced further apart. Ice floats.
    • Water's density is highest at 4°C (39.2°F)

    Water in Biochemical Reactions

    • Water is central to crucial biochemical reactions, including photosynthesis and cellular respiration.
    • Photosynthesis converts water and carbon dioxide to glucose using sunlight.
    • Cellular respiration breaks down glucose to produce energy and water.

    Water as a Buffer

    • Water acts as a weak buffer, moderating changes in pH.
    • Small amounts of water molecules dissociate to form H⁺ and OH⁻ ions.
    • If an acid or base is added, these water ions moderate the change ensuring a relatively stable pH.

    Acids, Bases, and pH

    • Acids release hydrogen ions (H⁺) into solutions, increasing acidity and lowering the pH.
    • Bases absorb hydrogen ions (H⁺), increasing basicity and raising the pH.
    • The pH scale (0-14) measures acidity or basicity, with pure water being neutral (pH 7).

    Neutralization

    • A neutralization reaction occurs when an acid and a base react to form water and a salt.

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    Description

    Explore the essential roles and unique properties of water in supporting life on Earth. This quiz covers the water cycle, distribution of Earth's water, and why water is fundamental to various organisms. Test your understanding of how water influences the biosphere!

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