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Hydrogen Bond

 
5.4 Hydrogen Bond
 
Introduction to Hydrogen Bond
  • Hydrogen bonds are attraction forces between hydrogen atom, H that has bonded with an atom of high electronegativity, such as nitrogen, N, oxygen, O or fluorine, F with nitrogen, N, oxygen, O or fluorine, F in another molecule.
  • For example, water molecule, H\(_2\)O.can form hydrogen bonds among water molecules, H\(_2\)O as below.
 
This image illustrates the formation of hydrogen bonds between water molecules (H2O). It is divided into four steps: 1. **Oxygen atom, O, has high electronegativity.** 2. **Water molecule, H2O, consists of two hydrogen atoms, H, and one oxygen atom, O.** 3. **Hydrogen, H, and oxygen, O, are bonded by sharing electrons with one another.** 4. **Attraction forces between hydrogen atom, H, from one water molecule with oxygen atom, O, from another water molecule forms a hydrogen bond.** The image includes a timeline-like layout with blue circles and text, and it is branded with the ‘Pandai’ logo.
 
Roles of Hydrogen Bond in Daily Life
  • Hydrogen bonds between protein molecules in the hair structure
  • Formation of hydrogen bond between protein molecule and water molecule
  • There are protein molecules that form hydrogen bonds among one another in the hair structure.
  • When hair is wet, protein molecules no longer form hydrogen bonds.
  • Instead, protein molecules form hydrogen bonds with water molecules, \(H_2O\).
  • Water molecules, \(H_2O\) will form hydrogen bonds with other hair protein molecules.
  • This causes hair to stick together.
  • The diagram below show hydrogen bonds between protein molecules in the hair structure.

This image illustrates the structure of hair at a microscopic level. On the left, a cross-section of a hair strand is shown. In the center, a zoomed-in view reveals the coiled protein molecules within the hair. On the right, a further magnified section displays the hydrogen bonds between the protein molecules, depicted as red dotted lines connecting the hydrogen (H) and oxygen (O) atoms.
 
Effect of Hydrogen Bonds on The Physical Properties of Substances
  • Compounds in the form of liquids reach the boiling point when the attraction forces between molecules are overcome.
  • In the covalent compound of ethanol, \(C_2H_5OH\), there are hydrogen bonds formed between molecules, other than weak Van der Waals attraction forces. 
  • Strong hydrogen bonds are difficult to break
  • More heat energy is required to overcome the weak Van der Waals attraction forces, besides breaking the hydrogen bonds
  • The boiling point of ethanol,\(C_2H_5OH\) is high. On the other hand, molecules like chlorine, \(Cl_2\) which do not form hydrogen bonds have a lower boiling point compared to ethanol.
  • Ethanol, \(C_2H_5OH\) is also soluble in water.
  • The solubility of ethanol, \(C_2H_5OH\) in water is due to the formation of hydrogen bonds between the ethanol molecule, \(C_2H_5OH\) and the water molecule, \(H_2O\). 
 

 

 

 

The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of pandai.

Hydrogen Bond

 
5.4 Hydrogen Bond
 
Introduction to Hydrogen Bond
  • Hydrogen bonds are attraction forces between hydrogen atom, H that has bonded with an atom of high electronegativity, such as nitrogen, N, oxygen, O or fluorine, F with nitrogen, N, oxygen, O or fluorine, F in another molecule.
  • For example, water molecule, H\(_2\)O.can form hydrogen bonds among water molecules, H\(_2\)O as below.
 
This image illustrates the formation of hydrogen bonds between water molecules (H2O). It is divided into four steps: 1. **Oxygen atom, O, has high electronegativity.** 2. **Water molecule, H2O, consists of two hydrogen atoms, H, and one oxygen atom, O.** 3. **Hydrogen, H, and oxygen, O, are bonded by sharing electrons with one another.** 4. **Attraction forces between hydrogen atom, H, from one water molecule with oxygen atom, O, from another water molecule forms a hydrogen bond.** The image includes a timeline-like layout with blue circles and text, and it is branded with the ‘Pandai’ logo.
 
Roles of Hydrogen Bond in Daily Life
  • Hydrogen bonds between protein molecules in the hair structure
  • Formation of hydrogen bond between protein molecule and water molecule
  • There are protein molecules that form hydrogen bonds among one another in the hair structure.
  • When hair is wet, protein molecules no longer form hydrogen bonds.
  • Instead, protein molecules form hydrogen bonds with water molecules, \(H_2O\).
  • Water molecules, \(H_2O\) will form hydrogen bonds with other hair protein molecules.
  • This causes hair to stick together.
  • The diagram below show hydrogen bonds between protein molecules in the hair structure.

This image illustrates the structure of hair at a microscopic level. On the left, a cross-section of a hair strand is shown. In the center, a zoomed-in view reveals the coiled protein molecules within the hair. On the right, a further magnified section displays the hydrogen bonds between the protein molecules, depicted as red dotted lines connecting the hydrogen (H) and oxygen (O) atoms.
 
Effect of Hydrogen Bonds on The Physical Properties of Substances
  • Compounds in the form of liquids reach the boiling point when the attraction forces between molecules are overcome.
  • In the covalent compound of ethanol, \(C_2H_5OH\), there are hydrogen bonds formed between molecules, other than weak Van der Waals attraction forces. 
  • Strong hydrogen bonds are difficult to break
  • More heat energy is required to overcome the weak Van der Waals attraction forces, besides breaking the hydrogen bonds
  • The boiling point of ethanol,\(C_2H_5OH\) is high. On the other hand, molecules like chlorine, \(Cl_2\) which do not form hydrogen bonds have a lower boiling point compared to ethanol.
  • Ethanol, \(C_2H_5OH\) is also soluble in water.
  • The solubility of ethanol, \(C_2H_5OH\) in water is due to the formation of hydrogen bonds between the ethanol molecule, \(C_2H_5OH\) and the water molecule, \(H_2O\). 
 

 

 

 

The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of pandai.
Chapter : Chemical Bonds
Topic : Explaining the effect of the hydrogen bond on the physical properties of substances
Form 4 Chemistry
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