It looks like you've uploaded a page from a physics textbook or worksheet, specifically related to
capillary action and
surface tension, under the topic of "Capillarity" in a section titled "Liquids." The image contains:
- A diagram (Figure 2.1) showing a capillary tube inserted into a liquid.
- Two questions:
1. A multiple-choice question about the shape of the meniscus formed by a liquid in a capillary tube.
2. A second question asking to explain why a liquid rises in a capillary tube.
However, since I can't view images directly, I'll interpret based on your description and common textbook content.
Let’s go through the typical problem and its solution:
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Question 1:
> Which of the following best describes the shape of the meniscus formed when water is placed in a glass capillary tube?
Options:
A. Flat
B. Concave
C. Convex
D. Irregular
Answer: B. Concave
Explanation:
Water molecules are attracted to the glass surface (adhesion) more than they are attracted to each other (cohesion). This causes the water to climb up the sides of the tube, forming a
concave meniscus — the surface curves upward at the edges and dips down in the center.
This is due to
capillary action, which results from the interplay between:
-
Adhesive forces (between liquid and container),
-
Cohesive forces (within the liquid), and
-
Surface tension.
In contrast, mercury forms a
convex meniscus because cohesive forces dominate over adhesive forces.
---
Question 2:
> Explain why a liquid rises in a capillary tube.
Answer:
A liquid rises in a capillary tube due to
capillary action, which is caused by the combined effects of
surface tension,
adhesion, and
cohesion.
Here's how it works:
1.
Adhesion: The liquid molecules are attracted to the walls of the capillary tube (especially if the tube is made of glass).
2.
Cohesion: Liquid molecules are also attracted to each other.
3. When the tube is dipped into the liquid, adhesion pulls the liquid up along the sides of the tube.
4. Surface tension allows the liquid to form a curved meniscus and helps pull more liquid upward.
5. The liquid continues to rise until the
weight of the liquid column balances the upward pull from surface tension and adhesion.
The height to which the liquid rises is given by the
Jurin’s Law formula:
\[
h = \frac{2T\cos\theta}{\rho g r}
\]
Where:
- \( h \) = height of liquid rise,
- \( T \) = surface tension of the liquid,
- \( \theta \) = contact angle between liquid and tube,
- \( \rho \) = density of the liquid,
- \( g \) = acceleration due to gravity,
- \( r \) = radius of the capillary tube.
For water in a clean glass tube, \( \theta \approx 0^\circ \), so \( \cos\theta = 1 \), and the liquid rises significantly.
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Final Notes:
- Capillary action is important in plants (water transport through xylem), ink flow in fountain pens, and porous materials like paper towels.
- The narrower the tube, the higher the liquid rises.
If your image had different details or additional parts, please describe them, and I can tailor the answer accordingly!
Parent Tip: Review the logic above to help your child master the concept of physiology cell worksheet.
