Intermolecular forces and Shapes

Question 1

dispersion forces

Answer 1

These are the weak temporary attractive forces between atoms and molecules caused by an instantaneous temporary change in dipole moment, arising from the rapid movement of orbiting electrons.

Question 2

dipole-dipole forces

Answer 2

Dipole-dipole forces are forces of attraction between oppositely charged dipole of neighbouring molecules, these forces allow polar molecules to attract to one another.

Question 3

hydrogen bonding

Answer 3

Hydrogen bonds are directional forces that only occur in molecules that have an H-F, H-O, H-N arrangement of atoms. The hydrogen bond is due to the electrostatic attraction between a lone pair of electrons of a F, O, N atom and an H atom that is already covalently bonded to another F, O, N atom.

Question 4

melting point

Answer 4

the temperature where the phase change of solid to liquid occurs and the particles move freely within the liquid volume

Question 5

boiling point

Answer 5

the temperature at which the vapour pressure of a liquid equals the atmospheric pressure surrounding the liquid which causes the liquid changes into a vapour.

Question 6

evaporation

Answer 6

Evaporation occurs only at the surface of a liquid whereas boiling occurs throughout the whole liquid.

Question 7

heat capacity

Answer 7

Heat capacity is defined as the amount of heat energy required to raise the temperature of a given quantity of matter by one degree Celsius. Heat capacity for a given matter depends on its size or quantity and hence it is an extensive property.

Question 8

solubility

Answer 8

the solubility of substances in water, including ionic and polar and non-polar molecular substances, can be explained by the intermolecular forces, including ion-dipole interactions between species in the substances and water molecules, and is affected by changes in temperature. READ MORE ON NOTION

Question 9

surface tension

Answer 9

Surface tension is the force that arises from the attraction of the surface molecules to the bulk of the material which causes it to resist external forces. Surface tension is shown by a liquid’s tendency to resist any increase in its surface area.

Question 10

capillary action

Answer 10

Capillary action is the process in which a liquid is drawn up a narrow tube. Capillary action is due to three main forces. These are the cohesive force, surface tension and adhesive force.
- The cohesive force is the intermolecular force between molecules in a substance that helps to maintain a certain shape of the liquid.
- Surface tension is present due to the cohesive forces at the surface of material and results in the surface of the fluid being under tension.
- The adhesive force are the electrostatic forces of attraction between unlike molecules.

Question 11

vapour pressure

Answer 11

vapour pressure is a measure of the tendency of a substance to evaporate and is measured in kPa (kilopascals)

Question 12

VSEPR

Answer 12

• Valence Shell Electron Pair Repulsion
• Assumes that each atom in a molecule will be positioned so that there is minimal repulsion between the valence electrons of each atom.

Question 13

shapes

Answer 13

• The arrangement of these electrons (bonding and nonbonding) leads to specific shapes of molecules
• These include:
  
  • linear
  • triangular planar
  • tetrahedral
  • bent
  • pyramidal

Question 14

linear

Answer 14

2 BONDING PAIRS, NO LONE PAIRS

Question 15

triangular (trigonal) planar

Answer 15

3 BONDING PAIRS, NO LONE PAIRS

Question 16

tetrahedral

Answer 16

4 BONDING PAIRS, NO LONE PAIRS

Question 17

bent

Answer 17

2 BONDING PAIRS, ONE OR TWO LONE PAIRS

Question 18

pyramidal

Answer 18

3 BONDING PAIRS, ONE LONE PAIR