SS1: PHYSICS – 3RD TERM
Production of Electric Current | Week 16 Topics|1 Quiz
Energy used in Generating Electricity - Chemical Energy
Energy used in Generating Electricity - Heat Energy
Energy used in Generating Electricity - Solar Energy
Energy used in Generating Electricity - Mechanical Energy
Electric Circuit - Components & Symbols
- Energy used in Generating Electricity - Chemical Energy
Electric Current | Week 25 Topics|1 Quiz
Electrical Resistance of a Conductor | Week 35 Topics|1 Quiz
Particulate Nature of Matter | Week 45 Topics|1 Quiz
Crystalline and Non-crystalline Substances | Week 53 Topics|1 Quiz
Elastic Properties of Solids | Week 6 & 74 Topics|1 Quiz
Fluids at Rest & in Motion | Week 8 & 96 Topics|1 Quiz
Solar Collector3 Topics|1 Quiz
Cohesion & Adhesion
Cohesion is the force of attraction that exists between molecules of the same substance e.g the force of attraction between molecules of water (water and water).
Adhesion is the force of attraction between molecules of different substances. e.g the force attraction between water and a glass surface.
Cohesion and adhesion, as defined above, explain the different actions of water and mercury when spilt on a clean glass surface.
The Reason Water Wets Glass:
The force of attraction between molecules of different substances (adhesion), like water and glass surface, is stronger than the cohesive force existing between molecules of water, hence, water spreads out on the surface of the glass and wets the glass.
Reason Why Mercury Does Not Wet Glass:
When mercury is spilt on a glass surface, the mercury does not spread or wet the glass, instead, it forms goblets or spherical beads (balls). This is due to the fact that the cohesion force of mercury molecules is stronger than the adhesion force between mercury molecules and glass molecules.
This also explains why the mercury level in the tube will fall as discussed in the previous topic.
So we can see why mercury does not wet glass whereas water wets glass.
These adhesion and cohesion forces are responsible for the rising and fall of liquid in a capillary tube. The adhesive force pulls water up the side of the tube. Causing water to creep up inside the tube.
Capillarity action causes;
1. Water to rise in the stem of a plant.
2. Blotting paper to absorb ink.
3. Blood to spread through fine capillary tunnels in the body.