Buoyancy Lesson

Last Updated: September 5th, 2008.

Buoyancy Lesson Plan Lesson Objectives: • • •

Understand the concept of density Understand the concept of buoyancy Be able to apply these concepts to real-world examples

Supplies: • • • • •

One can of Coke, one can of Diet Coke Three small Tupperware (one filled with sand, one with beans, and one with cotton) Tin Foil Pennies Large tub to be filled with water

Note for this lesson that experiment 2 “Aluminum Foil Boats” takes significantly longer than experiment 1 “Diet Coke v. Coke”. The tutors giving this lesson should take this into account and make sure that they leave sufficient time to complete experiment 2. In the past, students have really enjoyed experiment 2, so try your best to make as much time for this experiment as you can. Good luck!

Tutor introductions: Introduce yourself. Tell the students where you go to school, what your major is, how old you are, etc. You will be working with this class for several weeks, so it’s good to get to know them!

Experiment 1: Diet Coke v. Coke (~20 min total) Supplies: One can of Coke, one can of Diet Coke, three Tupperware (one filled with sand, one with beans, and one with cotton), and a large tub filled with water. 1. (10 min.) Show the students the three Tupperware containers and explain that you are going to put them in the water. Ask them to make a hypothesis about which ones will sink and which ones will float, and tally their answers on the board.

Last Updated: September 5th, 2008.

a. Place the Tupperware in the water one at a time to verify the students’ hypothesis. Talk about why some floated and why some sank. b. Introduce the concept of density. Density is mass divided by volume, and it is what we use to determine if something will sink or float in water. (You may want to make sure the students are comfortable with the concept of mass and volume). If the object is denser than water, it will sink, and if it is less dense it will float. 2. (10 min.) Now show them the two equal-sized cans of soda, and ask them to form another hypothesis: will both sink, both float, or one sink and which one? a. Drop the cans into the water at the same time. Let them settle. Do this again or let one of the students try so they can see there is no trick. Record the result on the board. b. Ask the students based on the experiment, which can of soda is more massive and why? If they are having trouble, remind them of the definition of density and ask them which is denser (the regular coke is denser because it sank while the diet coke floated). If they are still having trouble, explain that the denser can must be more massive because they both have the same volume. The regular Coke has more “stuff” in the same sized can. See if they can guess what the difference might be. (It is likely the sugar in the regular Coke that makes it more dense than the diet Coke).

Experiment 2: Aluminum Foil Boats (Remaining lesson time) Supplies for each group: about 2 ft of foil (and an extra in reserve in case of tearing), one bucket filled with water, bag of pennies. 1. (5 min) Divide the class into groups of 3-4 students. Distribute the foil to each group. Explain that they are to build a boat out of the foil to hold as many pennies as possible without sinking. Draw an example boat on the board without being too specific. Let them figure out how to best build their boat. 2. (15 min.) Students make their boats. Wander around the classroom to make sure no one has any questions.

Last Updated: September 5th, 2008.

3. (15 min.) Test the boats. Have the groups come up to the front of the class one at a time, and let them choose someone to place the pennies in the boat. Count how many pennies each boat holds and record that number on the board. 4. (5 min) Discuss what worked well in a boat design and what didn’t. If there is time, ask generally about why boats float (they should be reminded of the relationship between density and buoyancy).

Scientific background for tutors: Students may wonder why two boats that are exactly the same in design sink with different numbers of pennies aboard. The answer probably lies in the distribution of the pennies. Putting all the pennies in one spot will make the boat sink, while distributing them evenly throughout the boat will allow the boat to hold more pennies. This is because the “boat" with its penny cargo does not act like one big mass. If at any point on the boat the density (mass/cross-sectional area of boat) of the stacked pennies is higher than the density of water, that part of the boat will sink. This will compromise the integrity of the boat, which will then cause the whole thing to sink.

If you have extra time at the end of the lesson, allow the students to ask you questions on either the particular experiment you just completed or about science in general. Direct the students’ questions to areas of science that you feel comfortable providing answers about. If you don’t know an answer to a students’ question, it is OK to tell them that you don’t know, but also tell them how you would go about finding the answer to their question , either through experimentation or research.