6.3 Water and Solutions

1. Properties of water:

A

Water is vital to life on Earth. Its properties allow it to provide environments suitable for life and to help organisms maintain homeostasis. Humans can survive many days without food, but can survive only a few days without water

B

Water is made up of one

oxygen atom and two

hydrogen atoms.

C

Water is polar. Its bent shape results in a slightly positive charge on the hydrogen atoms and a slightly negative charge on the oxygen. As a result, it forms hydrogen bonds with other water molecules

D

Water is called the universal solvent because many substances dissolve it .

E

Liquid water becomes more dense as it cools to 4oC. Yet ice is less dense that liquid water. As a result ,nutrients in bodies of water mix due to changes in water density during spring and fall. Also, fish can survive winter because ice floats—they continue to live and function in the water beneath the ice.

F

Water is cohesive – the molecules are attracted to each other due to hydrogen bonds. This attraction creates surface tension, which causes water to form droplets and allows insects and leaves to rest on the surface of a body of water.

G

Water is adhesive – it forms hydrogen bonds with molecules on other surfaces. Capillary action is the result of adhesion. Water travels up the stem of a plant, and seeds swell and germinate by capillary action. This movement also helps the plant maintain water pressure to hold itself up.

MIXTURES WITH WATER (page 163)

2. What is a mixture?

A mixture is a combination of two or more substances in which each substance retains its individual characteristics and properties.

3. Differentiate the following terms by completing the chart:

Term Definition

Solution A homogeneous mixture in which one substance is completely dissolved into another substance.

Solvent Part of the solution that does the dissolving

Solute Part of the solution that gets dissolved

4. Differentiate the following mixtures:

Name Definition A few examples

Heterogeneous mixture

A mixture all the items are distinct and always separate

Like items in a salad

Suspension Particles are mixed, but overtime will settle out and separate

Sand in waterOil and water

Colloid A mixture in which the particles are not dissolved in the solvent, but still will not settle out and separate.

Smoke, fog, mayonnaise, and blood

Solution A HOMOLOGOUS mixture in which the solute is completely dissolved within the solvent. It can not be filtered our and will not settle out.

Ex. Kool-aid in water

5. What is an Acid?

A substance that will release Hydrogen ions when dissolved in water. The more Hydrogen ions that are released, the stronger the acid. A

Examples: hydrochloric acid, sulfuric acid. Lemon juice, and vinegar

B

6. What is a Base?

A substance that will release hydroxide ions (OH-) when dissolved in water. The more hydroxide that is released, the stronger the base.

A

Examples: Baking soda, Milk of Magnesia, Liquid Plumber, Lye and oven cleaner.

7. Exactly what is the pH Scale?

A system where

Hydrogen – OH sensitive test strips reveal the presence and concentration of Hydrogen or –OH ions.

8. Sketch and label the pH Scale

9. How do you test for pH?

You use pH test strips. Tear you off a piece of the strip and stick it in your sample. Then match the color to the ph Chart. If the reading is 7 it is neutral. If it is below 7 it is an acid. The lower the reading, the stronger the acid. If the reading is above 7, it is a base. The higher the number the stronger the base.

10. What does “pH” mean??

This was developed really long ago. The exact meaning of the p has been forgotten. It is believed to stand for power and the H represents hydrogen. So, pH stands for the POWER OF HYDROGEN.

11 .What is a Buffer?

A buffer is slightly basic. When mixed with an acid, the buffer will neutralize the acid. Usually, a salt is produced as the acid goes back to a neutral pH.

12. What does medicine like Alka-seltzer, Maalox, Tums, or Rolaids do for you?

These medications are buffers. They neutralize the stomach acid and convert it to salt and water.

13. What do prescription medications like zantac, prilosec, or aciphex do for you.

These medications are acid blockers. They shut down the glands that produce stomach acid. They are not antacids.

14. What does Pepto-bismuth do for you?

This medication contains some antacid. The main ingredient in this medicine is clay. This medicine coats the stomach so the acid can’t get to the stomach lining.