Educational Activity

Title: Oh, how base this life can be!

Materials

* pH tests (see below)

* clean sample containers

* or samples of various common items (see list below)

* print out of student introduction

Objectives

During this activity students will:

* Conduct pH tests on various common items.

* Sort and compare their results.

* Critically analyze their results and hypothesize explanations to their results.

This activity can be integrated with a lesson on pH, and can be used to a)give the students an opportunity for active leaning by performing pH testing themselves and b)connect their learning with real research and their daily lives by comparing their pH results with the expeditions’.

Introduction to Students: pH is very important as it affects our daily lives as well as our research. For example, one of the ways researchers like Patty Fryer first began to hypothesize that the fluids coming out of the mud volcanoes originated from deep inside the mantle was by comparing their higher pH levels with the lower pH levels of the surrounding ocean water.

On the ship itself, we monitor and control various pH levels. An example of this is our water purification system, where the purified water is too basic (pH level of 9). Therefore it needs to lowered to a more tolerable level of 7.4. You can read more about it in day 16 of our daily updates, where we discuss the system in detail.

Safety is an issue as well, for example when handling the cores we need to keep in mind that they have a high pH level and are therefore basic. This means that we have to be careful when handling the cores. Most people can tolerate touching the cores with their hands, but it would not be healthy to smother your arms with the mud, and let it dry for a few hours, as it will dry out and damage your skin. More importantly it is important to keep it away from your eyes, which seems like an easy thing to do, until you’re pressure washing the mud off the coring equipment against the wind!

Activity Description

In this activity, students will determine whether something is an acid or a base and to what degree. Since there are many different methods of testing pH levels, we will not go into the step by step procedures, as each method is different. If you do not have a current pH testing kit, here are a few options.

a) A basic litmus test - This is a quick, simple and affordable method of testing whether a sample is an acid or a base. It’s drawback is that the litmus test will not give quantitative results about how acidic or basic the sample is. If students use this method, they will not be able to measure the degree of an item’s acidity or alkalinity.

b) Purple cabbage test - A less expensive method is to use purple cabbage to determine the pH levels of various solutions. The technique involve chopping, boiling, and straining the cabbage. Students use the strained liquid to get approximate pH levels according to various colors. This is a great activity in itself as it really involves the students. Its draw back is that it takes more time and resources, such as a cabbage and a stove. The advantage is that you can make cabbage rolls with the unused cabbage!

c) General purpose pH paper - This technique allows students to measure the entire range of pH levels with one strip of paper. It is a relatively affordable option, although more expensive than the previous two options. The paper is accurate to within half a pH unit.

d) Specialized pH paper kit - This is the most accurate method of pH testing of all four options. Its draw back is the cost. This method is accurate to within 1/10 of a pH unit. Generally, students do not need the precision offered by this caliber of test paper.

pH aboard the ship!

The following is a list of solutions and their pH levels, measured on or from the ship:

7.7 pH of sample from top of core

12.3 pH of sample from bottom of core

8.14 Ocean water at the surface.

7.6 Ocean water at a depth of 3500m

9.0 Water after reverse osmosis

7.4 Water coming out of our faucet

Core mud and pH paper

pH recorded by students!

Ask the students to take pH measurements of solutions found in their local neighborhood. At your discretion, the students can either take the pH tests with them and conduct them on site, or bring the samples back to the classroom for testing in clean containers. The following is a list of ideas.

* water from a faucet

* boiled water

* water from a local stream, lake, or puddle.

* water from a swimming pool.

* toothpaste solution

* soap / detergent

* cola

* saliva

* aspirin dissolved in water

* lemon

* baking soda

pH paper and aspirin

Have the students record their results and create charts that show the pH levels of the various solutions. Ask the students to sort their results in order from most acidic to most basic, and mark the neutral point of pH 7.

Discussion Questions

The following are some question that you can use to start a discussion.

* If water is supposed to be neutral, why do some (or all) of the water pH tests show a pH of > or < 7

* Was there a difference between faucet water and boiled water? If so, what do you think happened?

* Is the pH from your faucet different than from the ship's? If so, why do you think that is so? How is your water treated compared to the ship's water?

* Why do you think the pH is different at the bottom of the ocean (6000m down) than at the surface?

* Why do you think it is recommended to eat some food when taking aspirin. Do you think a can of cola would help the same way? Why or why not?

* Why would the pH levels be different in various parts of the same core?

 

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