Lesson Summary This lesson provides students with another piece of information to determine why some objects float and others sink.  They will compare the weight of a water-filled cylinder with the cylinders from previous lessons.  By weighing a cylinder of water and comparing the weights of solid cylinders that are the same size, students discover the relationship between the weight of water and buoyant force.  Through this investigation, students discover that objects that weigh more than the same volume of water sink, and objects that weigh less than the same volume of water float. Teacher Background The weight of the liquid, such as water, is more difficult to measure than the weight of a solid. The weight of the container, holding the water, must be considered when measuring the weight of the water. (see set-up tip #1) Set-up/Management Tips Remove the bobby pin clip for this activity.  (See page 98 of teacher manual for explanation) Set up multiple testing stations. The plastic cylinder with masking tape will be used in the next lesson. Literacy Support Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: Specific Weight