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Water Chemistry Activities
Activity One Materials:
Background: Procedure: 2. Have the teams predict how many drops of water they will be able to put on the coin. 3. Allow the students to slowly begin to place drops of water on the coin. Tell the students to add the drops one drop at a time for better results. Students will count the drops, and continue to add drops until the surface tension breaks, the water drop collapses, and spills over the side on the coin. 4. Have the students record the number of drops they were able to successfully place on the penny before the water drop collapsed. 5. Allow the other student on the team to repeat the activity. 6. Students report their team's data to the class. Assessment:
Extension:
Materials:
Background: Procedure: 2. Have the teams predict how many paperclips they will be able to float on top of the water. 3. Have the students attempt to place a paperclip on the surface of the water in the cup. (Hint: Have the students place the paperclip on the prongs of the fork, and gently lower onto the water.) 4. Have the students place as many paperclips as possible onto the surface of the water. Record the number of paperclips. 5. Allow the other student in the team to repeat the activity. 6. Students report their team's data to the
class. Assessment:
Extension: Objectives: Materials:
Background:
Because water is attracted to other substances, it has the ability to dissolve many materials. An example of one solid that water can dissolve is sugar. Sugar molecules also happen to be polar molecules, so the negative ends of sugar molecules are naturally attracted to the positive ends of water molecules, which will disperse the sugar and water molecules within a container. For example, if you were to place a teaspoon of sugar into a glass of iced tea, and stir, the sugar would eventually dissolve, making each sip of tea sweet, not pockets of "sweetness" within the glass. When substances are dissolved into water, like sugar, the sugar is known as the solute, and the water is known as the solvent. Water has the ability to dissolve many solids and liquids. That is why water is commonly called the "universal solvent". When two materials are put together, it is called a mixture. There are different types of mixtures, homogeneous or heterogeneous. When sugar and water are mixed, and the sugar seems to "disappear", it is known as a homogeneous mixture because it possesses the same properties throughout the mixture. A heterogeneous mixture consists of two or more regions that differ in properties. There are mainly two types of heterogeneous mixtures, colloidal dispersions and suspensions. The main difference is only the size of the items being mixed. A mixture of sand and water is an example of a suspension. When in suspension, the two or more properties do not settle quickly. In the case of sand and water, the particles of sand are constantly being "bumped" by water molecules and continue to stay in suspension for a while. Eventually, the sand will settle out, therefore, it is known as a suspension. A colloidal dispersion is a mixture in which the dispersed molecules are very small. So small that they may appear to have mixed together, but will eventually separate and settle out from the solvent. Procedure: 2. Teams will make visual observations about the contents of each container. Then the students will shake each container vigorously for 10 seconds. Once shaken, put the containers down and observe and record the changes in the mixtures over the next five minutes. Dissolving Liquids 2. Observe and record what happens in each cylinder. Assessment:
Objectives:
Background:
Background:
The abbreviated pH scale is a common way to represent the concept of pH, but lacks to convey an important concept about pH. The pH scale is a logarithmic scale, meaning that every step on the scale represents a multiplication of 10. If the pH of a solution decreases by one pH unit, that represents a tenfold increase in the concentration of hydrogen ions. For example, Lemon juice, with a pH of 2 (100,000 H 3O+ ions) is 10 times more acidic than soda with a pH of 3 (10,000 H3O+ ions). This aspect of the pH scale is shown nicely in this pH scale graphic.Even after explanation, this still can be an abstract concept for some
students. This activity is designed to offer a sense of scale to a
pH scale for students, showing just how far apart the numbers should be on
a true pH scale. Students will quickly realize why the abbreviated
version of the pH scale in found in textbooks. NOTE:
Depending on the student's mathematical abilities, this lesson can be
adapted to use Scientific Notation.
Procedure: 1. Have students review a standard (abbreviated) pH scale. 2. Explain to the class that the pH scale that they are accustomed to seeing is not entirely accurate. Explain that the pH scale is actually a logarithmic scale, meaning that every step on the scale represents a multiplication of 10 and that they are going to create an accurate representation of the pH scale. 3. In cooperative working groups or as a class, have students research or brainstorm various products and their corresponding pH. 4. Distribute the rolls of register tape, colored pencils, rulers, yardsticks and calculators. 5. Have the students unroll and find the approximate middle point of the strip of receipt tape. NOTE: To conserve class time, complete this step for the students prior to class. 6. Have the students label the middle point as pH 7 - neutral. 7. Have the students measure 10 centimeters to the right of pH 7 and label that point pH 8. If the students found products with pH 8, have them list the products on the receipt tape. 8. Have the students measure 10 centimeters to the left of pH 7 and label that point pH 6. If the students found products with pH 6, have them list the products on the receipt tape. 9. Have the students calculate how far in centimeters pH 9 will be from pH 8. Measure to that point and label the receipt tape. If the students found products with the corresponding pH, have them list the products on the receipt tape. 10. Have the students calculate how far in centimeters pH 5 will be from pH 6. Measure to that point and label the receipt tape. If the students found products with the corresponding pH, have them list the products on the receipt tape. 11. Continue procedure until students run to the end of the paper (which will happen very quickly). 12. Have the students continue their calculations to determine
how much more receipt tape they would need to complete the pH scale to
scale. Assessment: 1. Why do you think an abbreviated pH scale is used
in textbooks? 3. How much more basic is a solution with a pH of 12 than a solution with a pH of 9? 3. How much more acidic is a solution with a pH of 3 than a solution with a pH of 8? 4. How much more basic is a solution with a pH of 11 than a solution with a pH of 5? 5. How long of a piece of paper would you need to draw a complete pH scale (using centimeters)? 6. Why do you think a change in a
body of water's pH level of even one pH unit could be deadly for the
organisms that live in the water?
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