Properties of Water- Cohesion and Adhesion: Videos & Practice Problems

Water exhibits unique properties of cohesion and adhesion due to hydrogen bonding. Cohesion refers to water molecules sticking to each other, while adhesion involves water molecules adhering to other polar or charged surfaces, like glass. These properties contribute to water's high surface tension, allowing objects like paper clips to float on its surface. Understanding these characteristics is crucial as they play a significant role in water's function as a solvent for life, impacting biological processes and ecosystems.

Properties of Water- Cohesion and Adhesion

Water exhibits two fundamental properties: cohesion and adhesion, which are essential for understanding its behavior in various contexts. Cohesion refers to the tendency of water molecules to stick together, primarily due to hydrogen bonding. This means that water molecules are attracted to other water molecules, creating a cohesive force that contributes to phenomena such as surface tension. Surface tension is defined as the measure of difficulty in breaking the surface of a liquid, allowing objects like a paper clip to float on water without sinking, as long as the surface is not disturbed.

On the other hand, adhesion describes the ability of water molecules to adhere to other substances that are not water, such as glass. This occurs when water molecules interact with polar or charged surfaces, allowing them to stick to these materials. The combination of cohesion and adhesion results in water's high surface tension, which is a unique characteristic not commonly found in most other liquids.

These properties of water are crucial for its role as a solvent in biological systems, enabling it to dissolve various substances and facilitate essential processes for life. Understanding cohesion and adhesion provides insight into the behavior of water in nature and its significance in supporting life.

Properties of Water- Cohesion and Adhesion Example 1

Cohesion, surface tension, and adhesion are essential properties of water molecules that arise from hydrogen bonding. These properties are crucial for various biological and physical processes. Cohesion refers to the attraction between water molecules, which allows them to stick together, contributing to phenomena such as water droplets forming on surfaces. Surface tension is a result of this cohesive force, creating a "skin" on the water's surface that enables small objects to float or insects to walk on water. Adhesion, on the other hand, describes the attraction between water molecules and other substances, which is vital for processes like capillary action in plants.

Water's unique properties stem from its molecular structure, where each water molecule (H₂O) is held together by polar covalent bonds. This polarity leads to the formation of hydrogen bonds between water molecules, significantly influencing their behavior. Understanding these properties is fundamental in fields such as biology, chemistry, and environmental science, as they play a critical role in processes like nutrient transport, temperature regulation, and the behavior of ecosystems.

Which of the following effects can occur because of the high surface tension of water?

• A. Lakes cannot freeze solid in winter even with extremely low temperatures.
• B. A spider can walk across the surface of a small pond.
• C. Oganisms can resist temperature changes, although they give off heat due to chemical reactions.
• D. Sweat can evaporate from the skin, helping to keep people from overheating.

Answer: (B)

Cohesive forces in liquid water occur when:

• A. The H atoms on molecules of H₂O hydrogen bond to O atoms on adjacent molecules of H₂O.
• B. The H atoms on molecules of H₂O hydrogen bond to other H atoms on adjacent molecules of H₂O.
• C. The atoms on molecules of H₂O hydrogen bond to other O atoms on adjacent molecules of H₂O.
• D. None of the above are correct.

Answer: (A)

Here’s what students ask on this topic:

What is the difference between cohesion and adhesion in water?

Cohesion refers to the ability of water molecules to stick to each other due to hydrogen bonding. This is why water droplets form and why water has a high surface tension. Adhesion, on the other hand, is the ability of water molecules to stick to other substances that are not water, such as glass. This occurs because water can form hydrogen bonds with other polar or charged surfaces. Together, these properties enable water to act as a solvent and play a crucial role in various biological processes.

How does hydrogen bonding contribute to water's cohesive and adhesive properties?

Hydrogen bonding is the key to water's cohesive and adhesive properties. In cohesion, hydrogen bonds form between water molecules, allowing them to stick together. This is why water has a high surface tension. In adhesion, water molecules form hydrogen bonds with other polar or charged surfaces, such as glass. This allows water to adhere to these surfaces. These hydrogen bonds are relatively strong, making water an excellent solvent and crucial for many biological processes.

Why does water have a high surface tension?

Water has a high surface tension due to its cohesive properties, which are a result of hydrogen bonding between water molecules. These hydrogen bonds create a 'film' on the surface of the water, making it difficult to break. This is why objects like paper clips can float on water if placed gently. The high surface tension is unique to water and is essential for various biological processes, such as the movement of water in plants through capillary action.

What role do cohesion and adhesion play in biological processes?

Cohesion and adhesion are crucial for many biological processes. Cohesion allows water molecules to stick together, facilitating the transport of water and nutrients in plants through capillary action. Adhesion helps water molecules stick to the walls of plant vessels, aiding in the upward movement of water from roots to leaves. These properties also contribute to water's role as a solvent, enabling it to dissolve and transport various substances essential for life.

How do cohesion and adhesion affect water's function as a solvent?

Cohesion and adhesion enhance water's ability to act as a solvent. Cohesion allows water molecules to stick together, forming a continuous column in plant vessels, which is essential for nutrient transport. Adhesion enables water to stick to other polar or charged substances, helping it dissolve a wide range of solutes. These properties make water an excellent solvent, crucial for various biochemical reactions and processes in living organisms.