Problem 12 - Campbell Biology

Question

Level \(3 :\) Synthesis/Evaluation SYNTHESIZE YOUR KNOWLEDGE How do cats drink? Scientists using highspeed video have shown that cats use an interesting technique to drink aqueous substances like water and milk. Four times a and milk. Four times a second, the cat touches the tip of its tongue to the water and draws a column of water up into its mouth (as you can see in the photo), which the shuts before gravity can pull the water back down. Describe how the properties of water allow cats to drink in this fashion, including how water's molecular structure contributes to the process.

Step-by-Step Solution

Answer

Cats drink by using cohesion, adhesion, and surface tension of water facilitated by hydrogen bonds to draw a water column into their mouths before gravity acts.

Step 1: Understanding the Drinking Technique

Cats touch the tip of their tongue to the water and draw a column of water up into their mouth, repeating this action four times a second. This process involves both physical interaction and the properties of water.

Step 2: Exploring Cohesion and Adhesion

Cohesion refers to the attraction between water molecules, which is due to hydrogen bonding. This allows water molecules to stick together. Adhesion is the attraction between water molecules and other surfaces, such as the cat’s tongue.

Step 3: Role of Surface Tension

Surface tension, caused by cohesive forces, makes the water molecules at the surface stick together, forming a column of water. When a cat touches its tongue to the water, surface tension helps maintain this column.

Step 4: Intermolecular Forces

Water has a polar molecular structure, with a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms. This polarity allows for hydrogen bonding, which is crucial for cohesion and surface tension.

Step 5: Applying the Knowledge

As the cat draws its tongue back to its mouth, water is pulled up due to surface tension and cohesion. The cat's quick action prevents gravity from pulling the column of water back down, making efficient use of the properties of water to drink.

Key Concepts

Cohesion and Adhesion

Cohesion and adhesion are two fundamental properties of water that play key roles in various natural processes, including how cats drink.
Cohesion refers to the tendency of water molecules to stick to each other, which is due to hydrogen bonds forming between them.
Thanks to these bonds, water molecules tend to form a continuous stream, resisting external forces that try to break them apart.
Adhesion, on the other hand, refers to the attraction between water molecules and other surfaces. In our context, it means water molecules sticking to the cat's tongue.
These properties allow a consistent stream of water to be maintained, which is crucial for the cat's drinking technique.

Surface Tension

Surface tension is another critical property of water that's essential for the way cats drink.
It's the reason why water can form drops and why insects can walk on water.
Surface tension arises because of the cohesive forces between water molecules at the surface.
When a cat touches the surface of the water with its tongue, it uses surface tension to its advantage.
The water sticks together and forms a column that the cat can pull into its mouth.
This cohesion at the surface resists being pulled apart, allowing the cat to create a column of water that is stable enough for repeated actions.

Hydrogen Bonding

Hydrogen bonding is a type of weak chemical bond that is exceptionally important in water's unique properties.
Each water molecule has a partial positive charge on its hydrogen atoms and a partial negative charge on its oxygen atom.
This polarity allows water molecules to form hydrogen bonds with each other.
These bonds are not as strong as covalent bonds but are strong enough to create cohesion and surface tension.
Hydrogen bonding holds water molecules tightly together, making it possible for cats to draw up a continuous column of water into their mouths.

Molecular Structure of Water

The molecular structure of water is a key factor in all its unique properties.
A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom, creating a 'bent' shape.
This results in a polar molecule with one side being slightly negative and the other side being slightly positive.
This polarity allows water to form hydrogen bonds, which are essential for cohesion, adhesion, and surface tension.
These properties are what enable cats to efficiently draw water up into their mouths by manipulating a column of water with their tongues.

Animal Physiology

Cats have specialized techniques that take advantage of water's properties to drink.
Their quick, repetitive motions are timed perfectly with the physical properties of water.
By touching the tip of their tongue to the water and drawing it quickly back into their mouth, they utilize surface tension and cohesion to form a stable column of water.
Then, they close their mouth before gravity can break the column.
This efficient method demonstrates a fascinating interplay between an animal's physiology and the unique properties of water.
Understanding how these properties work helps explain not just how cats drink, but also many other biological phenomena.