1.1 Structure of Hydrogen Bonding

• Water is composed of 2 main elements: oxygen and hydrogen, in a 2:1 ratio

• Covalent bond is the term used to describe the bond type in which atoms share electrons

• Oxygen is more electronegative compared to hydrogen, resulting in an unequal sharing of electrons between hydrogen and oxygen

• Covalent bonding can result in polarity where there are differences in atomic electronegatives, a water molecule has polarity

The subcomponents of biological molecules determine the properties of that molecule 

• A hydrogen bond is a strong bond interaction between the negative and the positive regions of two separate molecules

• Water can form hydrogen bonds with other water molecules or with other charged molecules 

• When two of the same molecules form hydrogen bonds with each other this is called cohesion

• When two different molecules form hydrogen bonds with each other it is called adhesion

Living systems depend upon properties of water 

• The hydrogen bonds between water molecules can result in surface tension

• Cohesion, adhesion and surface tension allow for water to demonstrate additional chemical behaviors known as emergent properties

• Life depends upon water’s properties 

Examples

• surface tension is a result of increased hydrogen bonding forces between water molecules at the surface

• Waters adhesive property gives water a high solvency ability in its liquid state

• Water’s cohesive property allows for unique hydrogen bond interactions to occur when making water is in a solid state, making ice (solid water) less dense than liquid water

• Waters cohesive property allows it to absorb a lot of thermal energy before changing chemical states. resisting sudden change in temperatures 

• Capilarily action is a result of both the adhesive and cohesive properties of water 

Key takeaways of 1.1 

• water contains 1 oxygen atom covalently bonded to 2 hydrogen atoms

• oxygen has a higher electronegativity compared to hydrogen resulting in a water molecule having polarity

• Polarity allows molecules to form hydrogen bonds when oppositely charged regions of two molecules interact

• The term cohesion refers to molecules of the same type forming hydrogen bonds with one another and adhesion refers to molecules that are different forming hydrogen bonds with each other 

• Living systems depending upon waters properties, like surface tension