Objectives:

1. To measure the tensile force acting on the metal ring just before the liquid layer breaks away.

2. Determine the surface tension from measured tensile force.

Surface tension is result when the surface of a liquid is acted upon by attractive forces from adjacent molecule towards one side. The liquid appears to have a membrane in its surface allowing some insects to walk through.

Theory:

Formula of surface tension is : σ = ____F____ 4∏Rwhere,F= Force ∏= 3.14 R= Radius

Tools:Precision dynamometer 0.1 NVernier caliperCrystallization dish, 95mm diameter, 55 mm high Laboratory stand Stand base, V-shape, 20 cm Stand rod, 75 cmClamp with hookDistilled water Ethanol

These are some situations involving surface tension:

1. Determine the diameter of the metal ring.2. Make the zero adjustment at the dynamometer using the movable

tube.3. Pour distilled water into the crystallization dish.4. Then, lower the clamp with the hook until the metal ring is

completely immersed.5. Carefully lower the laboratory stand and observe the tensile force at

the dynamometer.6. Take down the reading of the tensile force before the layer breaks

away.7. Pour out the distilled water from the crystallization dish.8. Dry the crystallization dish and the metal ring.9. Repeat the measurement with ethanol.

Procedures of the activity:

Activity:

Table 1

Radius of the metal ring = ____________m. Tensile Force of water = ____________mNSurface Tension = ____________mN/m

Measuring result for water (mN m-1)Literature value for water at 250C σ = 72 mN m-1

Measuring result for ethanol (mN m-1)Literature value for ethanol at 250C

σ = 22 mN m-1

Data:

Table 2