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 substances, 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 crucial for understanding its behavior in various contexts. Cohesion refers to the tendency of water molecules to stick together, a phenomenon primarily driven by hydrogen bonding. This means that water molecules are attracted to other water molecules, creating a cohesive force that contributes to water's unique characteristics.

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 interaction between water and glass is a prime example of adhesion, showcasing how water can form bonds with different types of molecules.

The interplay between cohesion and adhesion results in a relatively high surface tension for water. Surface tension is defined as the measure of how difficult it is to break the surface of a liquid. For instance, a paper clip can float on the surface of water if placed gently, demonstrating the surface tension created by the cohesive forces among water molecules.

These properties of water are not only fascinating but also essential for life. The cohesive and adhesive abilities of water enable it to act as an effective solvent, facilitating various biological processes. Understanding these properties lays the groundwork for further exploration of water's role in the environment and living organisms.

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 like water droplets forming on surfaces. Surface tension is the result of cohesive forces at the surface of water, creating a "skin" that can support small objects. Adhesion, on the other hand, describes the attraction between water molecules and other substances, enabling water to climb up plant roots and stems through capillary action.

Understanding these properties is vital, as they play significant roles in the environment and living organisms. For instance, the high surface tension of water allows insects to walk on its surface, while cohesion and adhesion are essential for the movement of water in plants. The underlying mechanism for these properties is the polar covalent bonds within water molecules, which lead to the formation of hydrogen bonds between them. This unique bonding structure is what gives water its remarkable characteristics, making it a vital substance for life on Earth.

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) Organisms 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.

• 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.

• 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 means that water molecules are attracted to other water molecules, creating a cohesive force. 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 molecules. Together, these properties contribute to water's high surface tension, allowing it to act as a solvent and support various biological processes.

How does hydrogen bonding contribute to the properties of water?

Hydrogen bonding is crucial for the unique properties of water. In cohesion, hydrogen bonds form between water molecules, allowing them to stick together. In adhesion, water molecules form hydrogen bonds with other polar or charged substances, enabling them to adhere to surfaces like glass. These hydrogen bonds also contribute to water's high surface tension, making it difficult to break the surface of the liquid. This high surface tension allows objects like paper clips to float on water and plays a significant role in water's function as a solvent in biological systems.

Why is surface tension important in water?

Surface tension is a measure of the difficulty in breaking the surface of a liquid with force. In water, high surface tension is due to the cohesive forces between water molecules, which are a result of hydrogen bonding. This property is important because it allows water to form droplets, enables insects to walk on water, and supports small objects like paper clips on its surface. High surface tension also plays a critical role in biological processes, such as the movement of water through plant vessels and the formation of cell membranes.

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

Cohesion and adhesion significantly enhance water's role as a solvent. Cohesion allows water molecules to stick together, facilitating the formation of a continuous column of water in plant vessels, aiding in nutrient transport. Adhesion enables water to stick to other polar or charged substances, helping it dissolve a wide range of solutes. These properties ensure that water can effectively transport nutrients, waste products, and other molecules within biological systems, making it an essential solvent for life.

What are some real-life examples of cohesion and adhesion in water?

Real-life examples of cohesion include the formation of water droplets and the ability of water to form a continuous column in plant vessels, aiding in nutrient transport. Adhesion can be observed when water sticks to the surface of a glass or when it climbs up a paper towel dipped in water. These properties are also evident in capillary action, where water moves through narrow spaces against gravity, such as in soil or plant roots. Together, cohesion and adhesion play vital roles in various natural and biological processes.