Water - Crucial for Maintaining Life

Water - Crucial for Maintaining Life

I. Introduction

• Explanation of why scientists search for water on other planets: Water is essential for life, and even trace amounts of it on another planet can indicate that life could or did exist there.
• Importance of water for life: Water is one of the more abundant molecules in living cells and is the one most critical to life as we know it.
• Percentage of water in the human body: Approximately 60-70% of the human body is made up of water, making it a vital component for human health.

II. Water's Polarity

• Formation of polar covalent bonds between hydrogen and oxygen atoms: The hydrogen and oxygen atoms in water molecules form polar covalent bonds. The shared electrons spend more time associated with the oxygen atom than they do with the hydrogen atoms.
• Slight positive charge on each hydrogen atom and a slight negative charge on the oxygen atom: As a result of these polar covalent bonds, water molecules have a slight positive charge on each hydrogen atom and a slight negative charge on the oxygen atom.
• Repulsion of slightly positive hydrogen atoms results in a unique shape: The repulsion between the slightly positive hydrogen atoms in water molecules results in a unique shape.
• Attraction between water molecules due to positive and negative charges: The positive and negative charges in different parts of water molecules attract other water molecules to form hydrogen bonds.
• Ability of water to dissolve hydrophilic (water-loving) polar molecules: Water also attracts other polar molecules, such as sugars, that can dissolve in water and are referred to as hydrophilic.

III. Water's Ability to Stabilize Temperature

• Hydrogen bonds allow water to absorb and release heat energy slowly: The hydrogen bonds between water molecules allow water to absorb and release heat energy more slowly than many other substances.
• Temperature is a measure of the motion (kinetic energy) of molecules: Temperature is a measure of the motion of molecules, with higher energy meaning higher temperature.
• Water moderates temperature changes within organisms and in their environments: Water can absorb a great deal of energy before its temperature rises, which means it moderates temperature changes within organisms and in their environments.

IV. Water's Solvency

• Water's polarity allows it to dissolve ionic compounds and polar molecules: Because of water's polarity, ionic compounds and polar molecules can readily dissolve in it.
• Water is a solvent capable of dissolving another substance: Water is, therefore, what is referred to as a solvent - a substance capable of dissolving another substance.
• Hydrogen bonds form between charged particles and surrounding water molecules: The charged particles will form hydrogen bonds with a surrounding layer of water molecules, allowing them to dissolve.

V. Water's Cohesive and Adhesive Properties

• Cohesion arises due to attraction between water molecules, keeping them together at the liquid-air (gas) interface: In cohesion, water molecules are attracted to each other due to hydrogen bonding, keeping the molecules together at the liquid-air interface.
• Surface tension is the capacity of a substance to withstand rupture under tension or stress: Cohesion gives rise to surface tension, the capacity of a substance to withstand rupture when placed under tension or stress.
• Adhesion is the attraction between water molecules and other molecules: Adhesion is the attraction between water molecules and other molecules, which is observed when water "climbs" up a straw placed in a glass of water.
• Cohesive and adhesive forces are essential for sustaining life: These cohesive and adhesive forces are important for sustaining life, such as the ability of water to flow up from the roots to the tops of plants to feed the plant.