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## To Float or Not to Float - A Lesson on Density

### Description

This lesson discusses density as a property of matter. Students will use the formula to calculate density to determine if an object/material will sink or float.

### Duration

Two 45-minute periods

### Learning Objectives

Students will learn:

• To explain and define density.
• To calculate density.
• To explain how to use density to identify a substance.

### Materials

• Ice Cubes
• Several blocks of wood and metal (or other materials)
• Rulers and Triple Beam Balance
• 2 Clay Balls (the clay should be the same kind and same amount)
• 2 Large Container with Water
• Graduated Cylinder and 40ml of water.
• Internet Access for additional support from Brain Pop and United Streaming. These websites requires a subscription
• SMART Board software, SMART Board, and projector
Provide students with:
• triple beam balance
• cooking oil
• water

### Procedure

First Day:

• Present the question: What would you rather carry through a dessert, a pound of feathers or a pound of lead?
• After discussing the students’ answers, point out that a pound of feathers is the same as a pound of lead. The main difference is that a pound of lead is smaller (has less volume) than a pound of feather.
• Review mass (the amount of material/”stuff” an object has) and volume (the amount of space an object takes up).
• Write the formula for finding density on the board.
• Identify the horizontal line in the formula means to divide the number on top by the number on the bottom.
• Try several examples before introducing density.
• Students can practice using the blocks of wood and metal to find density.
• After students practice, explain the concept of density (a measure of how tightly the matter of a substance is packed into a given volume).
• Density can also be used to identify particle substances because the density of a substance does not change regardless of the size or shape of the piece of substance.
• Allow students to work together to complete the Assessment Activity - Density
• Second Day:
• Show the class the clay boat and ball. Both objects should be made of the same kind of clay and the amount of clay.
• Invite the students to predict if the clay objects will sink or float.
• Have a large container with water to finish the demonstration.
• After they have discussed their predictions place the objects in the water. Let the students observe and discuss why the clay boat floats while the clay ball sinks.
• Finally explain that by changing the shape of the clay from a ball into a boat the volume of the clay was changed therefore changing the density.
• Students will then find the density of water and cooking oil. They will determine what the density of any object must be for a substance to float or sink when placed in water.
• There is an assessment activity – “To Sink or to Float" in Word format.

### Assessment

• Activity Sheet - Density
• Activity Sheet - To Sink or to Float