Look at the word where in paragraph 5. The word where in the passage refers to

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Read the passage below, and answer the vocabulary questions that follow.

The Processes of Diffusion and Osmosis

Diffusion is defined as a type of transport phenomenon, that is, a means by which matter moves from one place to another. Diffusion results from the kinetic energy of random motion that all matter possesses. To visualize how diffusion occurs, consider an eye dropper full of red food coloring squeezed into a large glass of water. Over time, the food coloring begins to disperse through the water, until both liquids are uniformly mixed and the water becomes slightly tinted. This is because the molecules of the food coloring are in constant motion, as are the water molecules. Technically, diffusion is the movement from areas of high concentration to areas of low concentration. In our example, the food coloring moves from an area of higher concentration (the food dye in the dropper) to an area of lower concentration (the dye-free glass of water). In this case, one would say the food coloring has diffused into the water.

For diffusion to occur there needs to be a gradient between two different material fields. In the example above, the two fields are the eye dropper and the glass of water. The rate of diffusion from one field to another is proportional to the difference in concentration of molecules in those fields. So while molecules move continuously in both directions, their tendency is to move from the more concentrated to the less concentrated molecular fields— which explains why the food coloring diffuses into the water, and not the other way around. In general, the greater the difference in concentrations between two molecular fields, the faster the rate of diffusion.

Osmosis is a particular type of diffusion that refers specifically to the movement of water across a semipermeable membrane. Generally defined, osmosis is simply an operation in which water diffuses through a membrane to an area with a larger quantity of dissolved substances, or solutes. In other words, if two solutions of different concentrations of dissolved material are separated by a wall that permits the smaller water molecules to pass through, but keeps out the larger molecules of the dissolved solids, then the water diffuses across the membrane from the less concentrated to the more concentrated solution. The solution containing more solutes has less water in it, and conversely, the solution with fewer solutes has more water in it. The water therefore will flow from high concentration to low concentration.

Given two solutions, the one with fewer solutes is said to be “hypotonic,” while the one with more solutes is called “hypertonic.” If an equal quantity of solutes exists on both sides of a membrane, an “isotonic” environment results, and no osmosis will occur.

Osmosis is tremendously important in biology, where water is the primary solvent, carrying many kinds of nutrients, and helping to regulate cells. Plants, for example, absorb water through osmosis. Because most plants are hypertonic in relation to the soil where they live, water moves automatically from the soil, through plant cell membranes, and into the roots. Without this process, plants would be unable to survive. Osmosis is an important process in humans and animals as well. Small blood vessels called capillaries wind through our bodies, coming in close contact with many cells. The exchange of important fluids between the capillaries and cells requires osmosis. Plasma, which is an important component of blood, is hypertonic compared to the surrounding cells. Therefore, liquids naturally move towards the capillaries, nourishing the blood in the process.

A process called reverse osmosis is employed by industrial chemists to achieve the purification of water. Because seawater has a high concentration of salt, it is hypertonic when separated from fresh water by a thin, semipermeable membrane. The fresh water crosses the membrane to unite with the seawater and become salt water. Chemists who need to distill seawater into fresh water for drinking or other purposes have found that by exerting pressure on the seawater, the natural procedure of osmosis is reversed and the pure water component passes from the salt water into the fresh water, leaving salt behind.

One question regarding osmosis is how cells can withstand the invasion of new water without bursting. Cells have a built-in security measure called turgor pressure . As new liquid moves into a cell, turgor pressure increases until it reaches a point whereby it is able to block incoming water and force it back out. The concept of turgor pressure is what allows industrial chemists to conduct reverse osmosis.

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Look at the word where in paragraph 5. The word where in the passage refers to

AnswerChoose the correct answer.Choose all that apply. Correct Partially correct Incorrect Don't Know

  1. A
    Correct Answer
    water
  2. B
    Correct Answer
    biology
  3. C
    Correct Answer
    osmosis
  4. D
    Correct Answer
    solvent
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