Surface Tension

CONTENT

• Definition of surface tension
• Effect of surface tension
• Application of surface tension
• Reduction of surface tension

SURFACE TENSION

1. Is the property of a liquid to make its surface behave as though it is covered by an elastic skin.
2. Is the force per unit length? Y= F/2L
3. Is the force acting parallel to the surface of the liquid?

EFFECTS OF SURFACE TENSION

1. Soap bubbles are spherical in shape
2. Water skaters are able to walk on the surface of water
3. Razor blade or needle gently placed on the surface of water floats
4. Spilled mercury on glass surface form spherical droplets

EVALUATION

1. Define surface tension
2. State the three effects of surface tension

APPLICATION OF SURFACE TENSION

1. Use in the manufacturing of rain proof or water proof
2. Absorption of ink with blotting paper
3. Rising of oil in lamp wicks
4. Movement of melted wax into the neck of a burning candle

REDUCTION OF SURFACE TENSION

1. Adding impurities such as detergent/soap, alcohol, oil, camphor, kerosene, grease
2. By heating the liquid.

EVALUATION

1. State three applications of surface tension
2. State two ways of reducing surface tension

READING ASSIGNMENT

Read more on surface tension – New school physics (pg102-103)

GENERAL EVALUATION

1. A platinum-resistance thermometer has a resistance of 5Ω at 0⁰C and 9Ω at 100⁰C. Assuming that resistance changes uniformly with temperature. Calculate the resistance of the thermometer when the temperature is 45⁰C
2. Give two reasons why water is considered an unsuitable liquid for thermometers.

WEEKEND ASSIGNMENT

1. Define surface tension. State the three effects of surface tension
2. (a) State three applications of surface tension (b) Two ways of reducing surface tension