Question

Cite two pieces of evidence to support the statement that water molecules in the liquid state exert considerable attractive force on one another.

Short answer

Water's surface tension and capillary action demonstrate significant intermolecular attractions.

Step-by-step solution

Identifying Evidence of Cohesion in Water

Water molecules in the liquid state exhibit strong cohesive forces, which is evident through surface tension phenomena. Surface tension in water is high due to hydrogen bonding between water molecules, leading to a "skin" on the surface that resists external force.

Observing Capillary Action in Water

Another piece of evidence for the attractive forces between water molecules is capillary action. This occurs when water rises up a narrow tube against gravity, which is possible because of the strong attractions (hydrogen bonds) between water molecules and between the molecules and the surfaces of the tube.

Key concepts

Surface Tension

Surface tension is a fascinating property of water and serves as a beautiful illustration of cohesion in action. It manifests as a "skin" on the water's surface that resists external force. This occurs because water molecules at the surface are not surrounded by similar molecules on all sides and hence, have a greater attraction towards each other. This creates a tension or a tight layer trying to minimize surface area.

The key player behind this phenomenon is hydrogen bonding. In water, hydrogen bonds form between the oxygen of one molecule and the hydrogen of another. These bonds are relatively strong compared to other intermolecular forces, which enhances the cohesion among water molecules.

• This cohesion makes water droplets hold together.
• It allows small insects, like water striders, to "walk" on the surface of water.

Surface tension is crucial in various biological and environmental processes. Understanding it helps in fields ranging from biology to engineering, as it influences everything from raindrop formation to the effectiveness of detergents.

Hydrogen Bonding

Hydrogen bonding is a unique type of connection that occurs between water molecules, and it's responsible for many of water's distinctive properties. Each water molecule is made up of two hydrogen atoms and one oxygen atom. Oxygen has a higher electronegativity, which means it attracts electrons more strongly than hydrogen. This results in slightly charged poles within the water molecule, which enables hydrogen bonding.

These bonds are not permanent; they're more like temporary "handshakes" that form and break rapidly. However, they are significant enough to influence properties like high boiling and melting points, and of course, cohesion and adhesion.

• Hydrogen bonds cause water to be a liquid at room temperature, unlike other molecules of similar size.
• They enable water to dissolve many substances, making it an excellent solvent.

Ultimately, hydrogen bonds are vital for life as they help in the formation of complex structures like DNA and proteins that are essential for living organisms.

Capillary Action

Capillary action is another intriguing water phenomenon that results from the strong interactions between water molecules. It's the ability of water to flow in narrow spaces without the assistance of external forces, like gravity. This is often observed when water rises in a thin tube, such as in plant veins or a drinking straw.

Capillary action occurs due to two forces: cohesion and adhesion. Cohesion is the attraction between water molecules while adhesion is the attraction between water molecules and the walls of the tube. When adhesion is stronger than cohesion, the water climbs up the tube, "pulling" itself along.

• This process is crucial for plants as it helps transport water from roots to leaves.
• It also plays a role in soil moisture movement and ink flow in pens.

Understanding capillary action not only gives us insight into how plants "drink" water but also helps in designing efficient water transportation systems in technology and agriculture.