Water and Solutions Section 3

Section 3 vocabulary ( 9 words) polar molecules, hydrogen bond, mixture, solvent, solute, acids, bases, pH, buffers.

polar molecules, ( 161) Molecules that have unequal distribution of charges, they have oppositely charges regions. This is due to the unequal sharing of the electrons In the polar covalent bonds It “shapes” the molecule!

7. Relate the shape of a water molecule to the distribution of electrons

5. Because of water’s chemical structure, the molecule is _polar___ allowing it to mix with and be a solvent to all things that are polar____. (Polar or non polar?)

hydrogen bond 161 A weak interaction involving a hydrogen atom and a fluorine, oxygen or nitrogen atom. It is a strong type of van der Waals force that holds water molecules together and gives water its special properties! Like holding hands the molecules are attracted to each other by their polarity!

mixture, 163 A combination of 2 or more substances in which each substance retains its individual characteristics and properties. Notes: New substances are not produced when a mixture is made, A solution is made. No chemical reaction takes place. A uniform mixture is called homogeneous.

solvent,163 In a solution the mixture in which the other substance is dissolved. Usually liquid. The tea is the solvent the sugar will be the solute

solute, 163 The substance dissolved in the solvent. Sugar is a solute in sweet tea Heat usually makes it dissolve faster,

8. What are the two parts of a solution? Solvent and solute In a sugar solution, sugar is the solute? What is the water? The solvent

SC.912.L.18.12 Discuss the special properties of water that contribute to Earth's suitability as an environment for life: cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. (MC AA) See page 162!

Surface Tension Water to Water bonds

cohesion Water to water Adhesion: water to something else

meniscus

Capillary Action Water “pulls” itself up a tube by its adhesion to the sides of the tube

pH activity Make a data chart of the items to be tested Test the pH and record the number item pH

Water Labs! Write the answers to the following activities on your own paper!

Penny activity Make a chart Drop water on the head side of a penny trial water Water with soap 1 2 3 average Make a chart Drop water on the head side of a penny Count the drops and record the number of drops that stay on the penny. Calculate the average of three trials. Add one drop of soap to the water and repeat the process.

WHY 1. Why did the water form a dome on the penny? 2. What is the reason it stayed on the penny so long? Use the information you know about water molecules to answer this question. 3. What happens to the number of water drops when soap is added to the water? Why?

WET 1. what do we call the water molecule because it has a positive side and a negative side? 2. What does it mean for water to wet something? 3. What type of molecules can get “wet” with water? 4. What type of molecules can not be wet but instead repel water?

chromatography 1. Draw a thin line on the bottom of your filter paper with a permanent black marker. 2. Do this on a second strip with a Vis a Vis marker. 3. hold the strip in the water so that only the very tip end is getting wet. 4. Allow the water to move up the paper strip. 5. Observe what happens.

S for sharpie V for Vis a Vis Thin line of the marker near the bottom

Don’t let it touch the bottom or the sides of the container but let the water touch the bottom of the paper strip! Do not let the line go under the water!!!

WHY? 1. Describe what happened to each of the strips. 2. Is the permanent marker soluble in water? Is it polar or non polar? 3. Is the VIS a VIS soluble in water? Is it polar or non polar? 4. What is true about the number of and types of pigments that make up the black marker?

Now… Draw 2 water molecules and show the electrons and charges. Show how each molecule is formed by showing the chemical bonds within the molecule as well as between the two molecules. Using the diagram, explain why water has special characteristics that make it so important to living organisms.

Diffusion Get two cups of water. Put several ice cubes in one cup. Drop food coloring into the cup and observe what happens. Make a hypothesis as to what would happen if the second cup of water if it were heated prior to the drops of coloring being added. Now try it. Explain why this happens.

Water Hydrogen bond

List the reasons why each property is important to life. See page 162 1. cohesive behavior: surface tension, droplets, 2. ability to moderate temperature: maintains homeostasis, environments suitable for life, 3. expansion upon freezing: mixes nutrients due to density differences, ice floats allowing fish to live under it, 4. versatility as a solvent: universal solvent, polar substances dissolve in it allowing for transport of many substances into and out of many organisms

6. What is it about water’s chemical makeup that makes it have these properties? It is polar and has hydrogen bonds that make it stick together causing cohesion and adhesion. This also causes the high Heat of vaporization and solubility For polar substances

acids, 164 Substances that release hydrogen ions when they are dissolved in water. H+ The more H+ the more acidic On the pH scale these are low numbers 0-6

bases,164 Substances that release hydroxide ions OH- ions when dissolved in water. Also called alkaline. Sodium hydroxide is an example. High numbers on the pH scale. 8 -14

pH, 165 The measure of the H+ ions in concentration is the pH Pure water has a pH of 7 the H= equals the OH- Test strips like these can be used to determine the pH. Proper pH is needed for reactions to occur and enzymes to work

Mixtures that can react with acids or bases and keep the pH within a particular range. The cell has buffers to keep the pH in the proper range for enzymes to function properly. Usually this is 6.5 to 7.5 but in the stomach this can be much more acidic and in the small intestine is can be more basic. buffers.165

pH A measure of hydrogen ion concentration Scale 1- 14 1-6 acid 7 neutral 8-14 base

pH paper Measure by a color change

9. Draw the pH scale. Label acid, base, and neutral 9. Draw the pH scale. Label acid, base, and neutral. Give an example of each.