Properties of Water: Hydrogen Bonding | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:

Introduction to Water
Chemical Structure of Water
The Polar Nature of Water
Hydrogen Bonding in Water

Introduction to Water

Water is a major component of all cells and has many important roles within organisms. Water has an important role in synthesising and breaking down biological molecules in condensation and hydrolysis reactions. Water is also a key reactant used in photosynthesis. Water also has many other essential roles for life due to its unique properties - these properties occur due to its structure.

Chemical Structure of Water

Water consists of 2 hydrogen atoms and 1 oxygen atom, giving it the molecular formula H2O. The hydrogen atoms are bonded to oxygen atoms through covalent bonds. Covalent bonds are formed when electrons are shared between two atoms in order to fill the outer shell. A covalent bond is one in which two atoms share the same pair of electrons.

The Polar Nature of Water

The electrons in the covalent bonds of water are not equally shared - they lie closer to the oxygen nucleus than the hydrogen nuclei. This is because the negative electrons are more attracted to the oxygen nucleus as there are more positively charged protons. The unequal sharing of the electrons result in the oxygen atom being slightly negative and the hydrogen atoms being slightly positive. The uneven distribution of charge across the water molecule makes it a polar molecule. Polar molecules are molecules that have an uneven distribution of charge.

Hydrogen Bonding in Water

The slightly positive hydrogen atoms in one water molecule are attracted to the slightly negative oxygen atom in another water molecule. This attraction is called a hydrogen bond and is weaker than a covalent bond but stronger than most intermolecular forces. A hydrogen bond is a weak interaction that occurs between a slightly negatively charged atom and a slightly positively charged atom. Although each individual hydrogen bond is weak, water forms many of these hydrogen bonds. The polar nature of water along with the formation of these hydrogen bonds give water many unique properties that are essential for life.

Summary

Water is an essential component of cells with major roles in metabolism, including condensation and hydrolysis reactions
Water is composed of an oxygen atom joined to two hydrogen atoms with covalent bonds
The negative electrons are more attracted to the oxygen atom than the hydrogen atoms
This results in an uneven distribution of charge across the molecule, making it polar
Hydrogen bonds occur between polar molecules like water as there is a weak attraction between slightly positive and slightly negative atoms
The polar nature of water and the formation of hydrogen bonds give water many unique properties that are essential for life

Видео Properties of Water: Hydrogen Bonding | A-level Biology | OCR, AQA, Edexcel канала SnapRevise