Properties of Water Quiz

Water's Properties

• Earth is approximately 71% water
• Human cells are 60-80% water
• Water is a polar molecule
• Water molecules are held together by hydrogen bonds

Properties of Water

• A water molecule (H₂O) is composed of one oxygen atom and two hydrogen atoms
• Water is polar because oxygen attracts electrons more strongly than hydrogen

Polarity of Water

• Oxygen end has a partial negative charge
• Hydrogen end has a partial positive charge
• This polarity creates hydrogen bonds between water molecules

Hydrogen Bonds

• Weak bonds, but numerous bonds are very strong
• Formed between a very electronegative atom (in a polar molecule) and a hydrogen atom
• Covalent bonds are strong bonds between atoms

Properties of Water Cont.

• Cohesion: Water molecules stick to each other
• Adhesion: Water molecules stick to other substances
• Less dense as a solid: Ice floats on water because ice is less dense than liquid water
• High heat capacity: Water resists temperature changes
• Universal solvent: Water dissolves many substances

Cohesion and Adhesion

• Cohesion describes water molecules attracting each other (e.g., surface tension)
• Adhesion describes water molecules attracting other substances (e.g., capillary action, water moving up plant stems)

Experiments

• Demonstrating cohesion: Count water drops on a penny
• Demonstrating density or surface tension: Place foil or paper clips on water. Observe what happens when foil is pressed. Observe what happens with different materials (e.g., paperclips)
• Demonstrating adhesion: Observe water moving up tubes

Density of Ice

• Ice is less dense than liquid water
• This is unusual and important because it allows ice to float on water, which insulates bodies of water during freezing temperatures

High Heat Capacity

• Water resists large temperature changes
• This helps moderate temperatures on Earth

Universal Solvent

• Water dissolves many substances
• Water is the solvent in many important biological processes (e.g., in living organisms)

Solutions

• Water is typically part of a mixture
• Water is a good solvent, meaning it is the solvent of life
• Solute: The substance that is dissolved in a solution
• Solvent: The substance that dissolves a solute
• Solution = solute + solvent (Example: Iced tea - water is the solvent; tea and sugar are the solutes)
• Water's polarity allows it to dissolve ionic compounds and other polar molecules
• Water is important for reactions like hydrolysis (e.g., macromolecule digestion)
• Experiments: Mixing water, oil, and alcohol to observe solubility

Homeostasis

• Water plays a major role in the regulation of body temperature, and transporting nutrients and wastes
• Water maintains a relatively constant temperature and resists drastic temperature changes, preventing damage to cells

Acids, Bases, and pH

• Water molecules form ions: Hydrogen (H+) and Hydroxide (OH-)
• Acid: A solution with lots of H+ ions (pH 0-7)
• Base: A solution with lots of OH- ions (pH above 7)
• Neutralization: Equal amounts of acid and base of the same concentration results in a neutral pH of 7 (H+ + OH- → H₂O)
• pH scale: Indicates the percent of H+ ions; ranges from 0-14; pH 7 is neutral
• Human blood maintains a pH of 7.35-7.45 (slightly basic)
• Buffers maintain this constant pH

Experiments (pH)

• Use pH test strips to determine the pH of various solutions like water, detergents, coke, vinegar, and hydrogen peroxide

Test your knowledge on the essential properties of water, including its molecular structure, polarity, and the significance of hydrogen bonds. This quiz covers key concepts like cohesion, adhesion, and the unique behavior of water in different states. Dive deep into the fascinating world of one of Earth's most vital resources!