AP Bio Properties of water worksheet

How is a water molecule like a magnet?

Because of the magnetic attraction water molecules exert on each other, liquid water tends to "stick together." You can see this when two water beads approach each other on a flat, smooth surface. When they get close enough, they magically merge into a single droplet. This property, called cohesion, gives water surface tension that insects with large feet exploit to be able to walk on the surface. It allows roots to suck water in a continuous stream and ensures that water flowing through tiny capillaries, such as veins, doesn't separate. The extra cohesion provided by hydrogen bonding compresses water together in the liquid state. When water freezes, electrostatic attraction/repulsion creates a lattice structure that is more spacious. Water is the only compound that is less dense in the solid state, and this anomaly means that ice floats. If it didn't, every marine ecosystem would die whenever the weather was cold enough for water to freeze.

How does water get to the leaves in the tops of the tallest trees against the force of gravity? Name the property(s) responsible for this and how it works

Capillary action occurs because water is sticky, thanks to the forces of cohesion (water molecules like to stay close together) and adhesion (water molecules are attracted and stick to other substances). Adhesion of water to the walls of a vessel will cause an upward force on the liquid at the edges and result in a meniscus which turns upward. The surface tension acts to hold the surface intact. Capillary action occurs when the adhesion to the walls is stronger than the cohesive forces between the liquid molecules. The height to which capillary action will take water in a uniform circular tube (picture to right) is limited by surface tension and, of course, gravity.Plants and trees couldn't thrive without capillary action. Plants put down roots into the soil which are capable of carrying water from the soil up into the plant. Water, which contains dissolved nutrients, gets inside the roots and starts climbing up the plant tissue. Capillary action helps bring water up into the roots. But capillary action can only "pull" water up a small distance, after which it cannot overcome gravity. To get water up to all the branches and leaves, the forces of adhesion and cohesion go to work in the plant's xylem to move water to the furthest leaf.

What causes surface tension in water?

The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. The molecules at the surface of a glass of water do not have other water molecules on all sides of them and consequently they cohere more strongly to those directly associated with them (in this case, next to and below them, but not above). It is not really true that a "skin" forms on the water surface; the stronger cohesion between the water molecules as opposed to the attraction of the water molecules to the air makes it more difficult to move an object through the surface than to move it when it is completely submersed.

Why does ice float on water?

The extra cohesion provided by hydrogen bonding compresses water together in the liquid state. When water freezes, electrostatic attraction/repulsion creates a lattice structure that is more spacious. Water is the only compound that is less dense in the solid state, and this anomaly means that ice floats. If it didn't, every marine ecosystem would die whenever the weather was cold enough for water to freeze.

List all the properties of water.

The main properties of water are its polarity, cohesion, adhesion, surface tension, high specific heat, and evaporative cooling.

Define cohesion in your own words. Give an example

The sticking together of particles of the same substance. A common example of cohesion is the behavior of water molecules. Each water molecule can form four hydrogen bonds with neighbor molecules. ... Another cohesive substance is mercury. Mercury atoms are strongly attracted to each other; they bead together on surfaces.

Why do humans sweat and dogs pant?

With far fewer effective places for dogs to have body-cooling sweat glands as compared to humans, dogs must rely on another mechanism to keep cool. The primary cooling mechanism for dogs is panting. By breathing air quickly over the wet surfaces of the inner mouth and lungs, the dog's pants accelerate evaporation cooling in much the same way that a breeze across a sweaty person's skin speeds up cooling. Dogs also have a different kind of sweat gland all over their body. But the sweat emitted from these glands are used to counter rapid rises of temperature in localized skin patches that could lead to burns, and not to cool the body as a whole.

Give an example that you observed of surface tension

A paper clip in a glass of water

Define adhesion in your own words. Give an example

Adhesion is the tendency of dissimilar particles or surfaces to cling to one another. One example of adhesion is water climbing up a paper towel that has been dipped into a glass of water, and one example of cohesion is rain falling as drops from the sky. During adhesion, water is attracted to other substances, causing the positive and negative molecules of the water to be attracted to the paper.

Write the chemical equation for water

H2O