Sequence | Background | Objectives | Materials | Activity | Extensions | Evaluations

TOPIC-TITLE Deep Sea Technology - Testing the Water AUTHOR Michael DiSpezio Roger Torda (JASON IV-Deep Sea Technology Authors) GRADE SUITABILITY Middle and High School SCOPE Oceanography

Sequence Explain to students that often it is important to collect water at varying depths so that some of the physical features, such as temperature, salinity, or dissolved chemicals, may be studied. If the water to be tested is close to the surface, it can be sampled quite easily by divers. However, if the water is to be collected at greater depths, other devices must be used. Ask: If you were going to design a bottle for collecting water at great depths, what characteristics would it have? Brainstorm with students for several minutes, noting their answers on the chalkboard. (Answers will probably include some of these: heavy enough to sink to the bottom, able to be stopped tightly so sample water is not lost or contaminated, and able to be cleaned thoroughly between uses so samples will be pure.) Tell the class they are going to be making a collection bottle similar to the ones the JASON Project scientists will use. < < go top

Background Summary Collecting equipment, similar in principle to the water collector described here, will be used to take samples from the areas close to the vents and at varying depths all the way down the water column in the Guaymas Basin. < < go top Objectives Students will be able to do the following: Describe how water samples are taken from the deep sea. Follow procedures to test water samples. < < go top Materials One small glass soda bottle (or comparable heavy glass bottle) 3-5 m (10-15 ft) cotton rope or cotton clothesline One rubber stopper to fit the soda bottle One screw about 2.5 cm long Metric ruler Waterproof marker One 500-g (1-lb) fishing weight, or other weight heavy enough to sink the bottle Approximately 30 cm (1 ft) mason cord or household string Water for testing (A natural body of water outdoors is ideal.) Celsius thermometers < < go top Activity Divide the class into small groups and provide each group with materials. Give these directions: Tie one end of the rope around the neck of the bottle, making sure it is securely knotted. Cut off the short end as close to the bottle as possible. Carefully force the screw through the center of the rope at a distance of 8 centimeters (3 inches) from the knot, then screw it into the center top of the stopper. Using knots and waterproof marker, mark off the line from the top of the stopper to the end of the line in equal increments (centimeters). Use the string to fasten the fishing weight to the bottom of the bottle. Take students with their bottles to a body of water for testing. Give students these directions: Put the stopper in carefully and securely, but not too tight for easy removal. Decide which mark on the line the bottle will descend to, then gently lower the bottle to the desired depth. Give the line a quick jerk to pull the stopper from the bottle. Large bubbles will rise to the surface as the bottle fills. When the bubbles stop, the bottle is full. Pull it quickly to the surface. Take the temperature of the sample immediately and record it. < < go top Possible Extension The sample can be carefully poured into labeled bottles to be tested back in the lab for salinity, dissolved oxygen, or other dissolved chemicals. Samples can be taken at different depths and comparisons can be made. < < go top Teacher Evaluation Build a discussion around these questions: Why is it necessary to place a weight on the bottom of the bottle? (Otherwise the air inside would make the bottle float.) Why doesn't water from other depths get into the bottle as it is being pulled to the top? (The bottle is already full, and it is pulled straight up to the top.) Why is it necessary to test the temperature as soon as the bottle is pulled up? (The temperature will soon change to that of the surrounding air.) < < go top