Overview
This lecture explains the properties of water, focusing on its chemical structure, hydrogen bonding, and how these characteristics make water vital for human life.
Structure of Water and Hydrogen Bonding
- Water (Hâ‚‚O) consists of two hydrogen atoms and one oxygen atom connected by covalent bonds.
- The oxygen atom has a partial negative charge; hydrogen atoms have partial positive charges, making water a polar molecule.
- Hydrogen bonds form between the positive hydrogen of one water molecule and the negative oxygen of another.
Importance of Water as a Solvent
- Water makes up about 50% of human blood, mainly as plasma.
- Plasma dissolves and carries hydrophilic substances like glucose, amino acids, and salts.
- Substances that dissolve in water are called hydrophilic; water is often called the "universal solvent."
- Water dissolves polar and charged molecules, aiding transport in blood and other fluids.
High Specific Heat Capacity of Water
- Water requires more heat to raise its temperature by 1°C compared to substances like ethanol.
- High specific heat capacity means water resists rapid temperature changes.
- Hydrogen bonds must be broken before water molecules can move faster and increase in temperature.
- This property stabilizes body temperature and aquatic environments against external temperature changes.
High Latent Heat of Vaporization
- Water needs a large amount of energy (heat) to change from liquid to vapor.
- Sweating uses water's high latent heat of vaporization to absorb body heat and cool the body effectively.
- More energy is required to evaporate water than other liquids due to hydrogen bonding.
Key Terms & Definitions
- Covalent bond — a chemical bond where two atoms share electrons.
- Hydrogen bond — a weak attraction between a hydrogen atom (partial positive) and an electronegative atom (partial negative).
- Polar molecule — a molecule with regions of partial positive and negative charge.
- Solvent — a liquid in which substances (solutes) dissolve.
- Hydrophilic — substances that dissolve easily in water.
- Specific heat capacity — the amount of heat needed to raise the temperature of 1g of a substance by 1°C.
- Latent heat of vaporization — energy required to turn liquid into vapor at a constant temperature.
Action Items / Next Steps
- Review the previous video on water’s molecular structure and properties.
- Prepare for future discussions on blood functions (upcoming Chapter 8 lesson).