9 Hydrogen Bonds Make Water Amazing

Polar Covalent Bonds and Their Role in Water

• Polar covalent bonds are a key feature in water molecules, where hydrogen and oxygen atoms are linked through these types of bonds. This affects how water molecules interact with each other, leading to unique properties.

Bonds Overview

Types of Bonds

• Nonpolar Covalent Bond:

  • Electrons shared equally between two atoms.

  • No charges on atoms. Example: Cl -- Cl.

• Polar Covalent Bond:

  • Electrons shared unequally, resulting in partial charges on atoms. Example: H -- Cl.

• Ionic Bond:

  • Complete transfer of electrons resulting in full charges on ions. Example: Na+ and Cl-.

Learning Objectives

• This lesson aims to help students:

  1. Describe conditions necessary for and the characteristics of hydrogen bonds.

  2. Analyze the structure of water molecules and the implications of hydrogen bonds within them.

  3. Understand the characteristics of water including: solvency, chemical reactivity, thermal stability, and lubrication.

Importance of Water’s Qualities

• Water's unique characteristics, enhanced by hydrogen bonding, allow it to support life. These include its properties of cohesion, adhesion, and surface tension, which are critical for various biological functions.

Drawing Water Molecules

• Students are encouraged to illustrate at least five water molecules, showing the partial charges on oxygen and hydrogen, and drawing dashed lines to represent hydrogen bonds between adjacent molecules.

Functions of Hydrogen Bonds

Properties of Water

1. Cohesion: Water molecules stick to themselves, leading to surface tension.

2. Adhesion: Water adheres to polar surfaces.

3. Surface Tension: Water minimizes its surface area, allowing objects to float.

4. Capillary Action: Water can move into small spaces without energy input.

5. Solubility: Water acts as a universal solvent, facilitating many chemical reactions.

6. Increased Chemical Reactivity: Some reactions are dependent on a water environment.

7. Thermal Stability: Water changes temperature slowly, making it stable for organisms.

8. Lubrication: Water is used in joints to minimize friction.

Types of Hydrogen Bonds

• Intermolecular Hydrogen Bonds: Bonds formed between different molecules, like water molecules.

• Intramolecular Hydrogen Bonds: Bonds within the same molecule, such as in DNA and proteins, crucial for their structure and function.

Review and Reflection

• At the end, students should reflect on the learning objectives and assess their understanding of hydrogen bonds and water's properties.