Question

LABORATORY WORK No. 11

Topic. Determination of the surface tension coefficient by the capillary method. Goal. Determine the surface tension coefficient, investigate the dependence of the surface tension coefficient on the concentration of impurities.
Equipment: capillary tube, vessels with liquids of different concentrations.
Progress
1. Determine its diameter from the inscriptions on the capillary tube.
2. Lower the capillary into tinted water (you can also use clean water, but tinted water is better visible in the capillary) and measure the height of its rise һ in the capillary. Considering the water to be pure, write down its density p and height h in the table.
3. Calculate the coefficient of surface tension of water according to the formula:
σ= pghD
4
4. Enter the result of the calculations in the table. 10.
Table 10
r, kg/m³
h, M
D, M
h
s, E/M
5. Perform an analysis of the errors made when performing the
trace
6. Repeat the experiment using aqueous solutions
Mal. 12.
copy-
larna
we are of known concentration. 7. Draw a graph of the dependence of the value of the surface tension coefficient of the solution on its concentration and draw a conclusion.
tube in liquid

Answer 1

Using the capillary action phenomenon and the given experimental formula, the surface tension of a liquid can be calculated based on the height the liquid rises in a capillary tube, the density of the liquid, and the diameter of the tube when the contact angle is zero.

Step-by-step explanation:

Understanding the Capillary Action and Surface Tension

The experiment described pertains to the capillary action observed when a capillary tube is dipped into a liquid, such as water. Capillary action occurs due to the balance between cohesive forces (between liquid molecules) and adhesive forces (between liquid molecules and the material of the tube). To determine the surface tension of the liquid, you can use a known relationship that links the height to which the liquid rises in the tube (h), the density of the liquid (p), the acceleration due to gravity (g, which is 9.8 m/s²), and the radius of the tube (r). The formula for the calculation of surface tension (σ) when the contact angle is zero (which means the liquid wets the tube completely) is:

σ = ​(2Tcosθh) / (rpg)

However, the given formula has been simplified to σ = (pghD) / 4, where D is the diameter of the capillary tube. In practical applications, this formula allows us to calculate the surface tension of liquids like water and observe how it changes with different concentrations of impurities.