### Keywords:

## Topic:

### Estimated Time Required:

### Target Grade (Ages):

### Diversity Indicators:

## Tab Wrapper

### Goals:

- Apply the concept of density to solving a problem.
- Work in small groups to design a solution to a problem.

### Prerequisites:

- How to use a ruler, balance, and graduated cylinder
- How to compare and contrast objects, using common physical properties, such as Mass, Volume, Weight
- How to solve basic math problems using a formula
- How to work in small and large groups
- The difference between the particles of a solid, liquid, and gas.

**The Big Objective**

Students will work in small groups to solve the following problem:

Your friends are locked inside of a museum after hours. The only way to get them out is to send the guard’s keys to them via a boat made out a 5”x5” square of tinfoil from your lunch. The boat must be able to float down a stream for twenty seconds, carry six keys, and fit through a small opening in the wall of the museum.

They will have two attempts: Once before the mini-lesson on density (i.e. using prior knowledge) and once after they have been introduced to the concept of density.

**Mini-Lesson Objectives**

- Students will understand the vocabulary and relationships between the words associated with density. (Reading & Writing)
- Students will measure the density of a regular shaped object using a ruler and balance. (Lab Skills)
- Students will compare the density of different objects based on their physical properties. (Observe, Compare, & Contrast)
- Students will model how to increase or decrease the density of an object using play dough as a model. (Hands-on)
- Students will model the distance between the particles of substances of various density using their bodies to represent the particles. (Kinesthetic Learning)

### Background:

I have included tips where appropriate within my procedure to support your lesson.

**Other Suggestions**

__Grouping__

- I would suggest groups no larger than four, but no smaller than three. You need enough students to learn how to listen to each other’s ideas, and argue in support of their opinion where appropriate.
- When making groups make sure to consider the strengths and weaknesses of each student. Group weaker students with stronger students.
- Make sure each group has a strong leader to keep the team on task and motivate the other members to participate.

__Notebooks__

- It is very important to have students keep detailed records of their work, because they will need to look back on it later to help improve their boat.
- Make sure to include sketches, calculations, brainstorming sessions, and especially VOCABULARY!
- Make sure each student keeps similar record of what transpires. I often have students state, "Our teammate is absent and they have all the work." This is completely preventable if you make it mandatory for all students to keep their own records.
*This can also serve as a tool for assessment.*

### Materials:

__For Each Group (@4 students per group)__

- 4, 5”x5” squares of aluminum foil. Two to build a boat before the introduction of density and two after.
- Ruler
- Balance
- 100mL graduated cylinder
- Small objects (more dense than water so they sink) that can fit in the graduated cylinder
- Several blocks of the same volume, but different masses. (Therefore, of different density)
- Small lump of clay/”Play-Doh”
- Access to water

__For the Whole Class (during demonstrations)__

- A cardboard box (shoe box size)
- Sand, Marshmallows, & Feathers (or any other materials you feel appropriate to place in the box to compare the density of different substances)
- 6 keys of average size
- Bucket to hold water (between one and three gallons, with an opening large enough to let your boats float)
- Poster of the vocabulary to remain posted throughout the lessons

### Procedure:

**Day 1 (of 9)**

- Introduce the challenge: You and your friends are on a field trip to a historic fort. When it’s time to go home on the school bus, you realize two of your friends are missing. You call them on their cell phone to find they are still inside of the museum. You run back to tell the guard. He tells you that the museum has been locked by an automatic system and the only way to open the doors is from the inside with his six keys. He suggests that there is a small stream that runs through the wall of the fort into the courtyard and that maybe you can get the keys in that way. You look through your book bag for some materials to help you get the keys in, but all you find is the leftover aluminum foil from your lunch. You suggest that you float the keys in using the aluminum foil as a boat. The guard says, “Go for it!” Can you save your friends???
- Distribute one 5”x5” square of foil to each group. Show them the keys. Tell them they have 20 minutes to design a boat that can float the keys down the stream for 20 seconds.
- Tell them to use their knowledge of boats and floating to design their boat.
- Tell them to first discuss their design as a team, and then actually manipulate the foil as the team decided.
- After 20 minutes have each group test their boat in front of the class. Have the “testing group” kneel around the bucket, and the rest of the class gather around and watch.
- Most likely, most, if not all, of the groups will fail. Most students either try to design their boat to look like a canoe, or a “classic origami boat.”
- After each group goes, have the other students discuss why each boat did or did not work. They should keep record of these comments in their notebooks.

**Day 2**

- Open up the class with the questions: “Why did some boats sink?” “Why do boats float?”
- Give students 5 minutes to discuss as groups and then record the answers in their notebooks. (Students should respond: “Boats are light.” “Boats are filled with air.” “Boats are …”)
- Use this time to introduce vocabulary, try to replace their words with the proper terms: Mass, Volume, Buoyancy. Have students record the vocabulary in their notebooks.
*Do not introduce density until later, as it is a much more complex idea.* - Have the students compare and contrast objects of various Mass, Volume, and Buoyancy out loud. (You need to demonstrate these objects in front of the class.)
- Distribute one block to each group. The blocks should all be the same size and shape, BUT have different masses.
- Have the students measure the volume of their block using a ruler and record results, showing the work in their notebooks. Then students should measure the mass of the block using a balance and record in notebooks.
- Have the students share their results with the class as well as predict if their block will float or sink and WHY!!!!

**Day 3**

- Give out the blocks to their respective groups.
- Ask students, “So, all of your blocks have the same volume, but different masses,
*why*?” Give them 4 minutes to discuss in small groups and then record their answers in their notebooks. - Lead students through a discussion of their answers, hoping to arrive at the idea that: “There is more STUFF packed into some blocks than others.”
- Whether or not students arrive at this idea, you need to model this idea for them in a demonstration.
- Present to them an “empty” shoe box.
- Ask them, “What’s in the box?” They may respond nothing, but remind them that air is in the box.
- Fill the box with feathers. Pass it around. Ask them if the box has more or less mass now and why?
- Fill the box with marshmallows. Pass it around. Ask them if the box has more or less mass now and why?
- Fill the box with something very dense (Textbooks?) Pass it around. Ask them if the box has more or less mass now and why?
- Ask your students: “Has the Volume Changed?” (Answer: No.)
- Ask your students: “Has the Mass Changed?” (Answer: Yes.)
- Ask your students: “Why? What is the difference between the Air, Feathers, Marshmallows, and Textbooks?”
- Lead students in a discussion that there is more space between the particles of the air than the particles of the feathers than the particles of the marshmallows than the particles of the textbooks.
- Give them the definition of density (How much STUFF is in a given SPACE, or the amount of MATTER in a certain VOLUME.)
__Exit Tickets__: Have students answer the following question before they leave and submit it as an exit ticket: Describe why the mass of the marshmallows is different from the mass of the textbooks, even though they take up the same volume? If they are the same size, shouldn’t they be the same weight?

**Day 4**

- Begin the class with the following “Bell ringer”: What does density mean to you? Can you describe two objects that have different densities? What makes them different?
- Compare and contrast the students answers, lead them into a discussion of solids, liquids, and gases.
- Remind them of the difference between the particles of a solid liquid and gas. Have them act out these differences with their hands.
- Once students seem to have the idea, have them all stand and gather in the middle of the classroom. Tell them that each one of them represents one particle of a substance.
- Ask them to arrange themselves as the particles of a solid. (All standing shoulder to shoulder and not moving.)
- Ask them to arrange themselves as the particles of a liquid. (Standing shoulder to shoulder, but moving and sliding past one another.)
- Ask them to arrange themselves as the particles of a gas. (Not touching, moving -- slowly for safety, and occasionally bumping into one another.
- Have the students draw the particles of a solid, liquid, and gas in their notebooks, ordering them from least to most dense.

**Days 5-6**

***This is an inquiry day***

- Go over the definitions of Mass, Volume, and Density with your students.
- Distribute a 1 lump of clay (larger than a golf ball, but smaller than a baseball) to each group of students.
- Ask students to reduce the mass of the clay. (They should remove some of the clay.)
- Ask students to increase the mass of the clay. (They should add the clay they removed to the ball.)
- Ask students to increase the volume of the ball. (They should spread the ball out as much as possible by flattening it.)
- Ask students to decrease the volume of the ball. (They should try to make the clay as small as possible by “squishing” it.)
- Introduce to the students the idea that you can manipulate the density of an object by changing its mass and/or volume.
*Prove this to them using MATH!*Introduce the formula for density:

*Density= Mass/Volume*

*Units= g/cm ^{3} or g/mL*

First, let them solve a basic problem. If the Mass of an object is 10g and the volume is 2cm^{3}, what is the density? 5g/cm^{3}.

Second, ask them to increase the mass of the object to 20g and solve for density. Ask, “Does the density increase or decrease?” (Density increases.) Ask them what they think would happen if they decrease the mass? (Density decreases.)

Third, Tell the students to write a RULE for how changes in mass affect density. (As mass increases, density increases. As mass decreases, density decreases.)

- Ask students to perform a similar task, except this time both increase and decrease the volume of an object without changing its mass.

First, ask students to create two math problems using the density formula, one where volume increases and the other where volume decreases.

Second, ask them to write a rule similar to the one created for mass, except this time for volume. (As volume increases, density decreases. As volume decreases, density increases.)

Finally, create a poster that describes the ways you can both increase and decrease density.

**Day 7**

Ok, this is the last day to “Float your Boat.”

- Have each team review their notes. Ask them to look at the first boat design and discuss its positive and negative features.
- Have each team discuss their new design and sketch it in their notebooks.
- Distribute 2 5”x5” squares of tinfoil to each group. Tell them to practice with the first one, and make their final design with the second one. Remind them that this is all the materials that they have and that they will not receive anymore.

** Make sure the six keys are available for the groups to view in order to estimate the dimensions needed for their boat.**

**Day 8**

- Have each group float their boats in front of the other groups as they did on day 1. Boats need to float for at least 20 seconds. (I always like to kick the bucket a little to simulate the ripples in a stream. The kids usually enjoy the action/suspense.)
- Have groups record in their notebooks the positive and negative aspects of each boat.
- Have them use these notes to describe why some boats float and others did not.
- Introduce the idea of buoyancy, and that an object will float in a liquid if it is less dense that the liquid it is floating in.

**Day 9**

Exam, Quiz, Project, Assesment

There are many extensions for this lesson as the concept of density applies to many topics. It is especially important when teaching earth science with regard to plate tectonics, as well as the formation of the Earth’s layers. Furthermore it is important throughout chemistry and physical science lessons.

I have included my assesment questions in my procedure where they are most applicable.

The idea for the "students trapped in the fort" and the "tinfoil Boat to carry six keys for 20 seconds" was taken from the unit provided by: It's About Time. Herff Jones Education. 7th Grade Science Unit: Digging in

All other lesson components were originally developed by Mr. Richard B. Akalski. Contact me at RAkalski@Aol.com for further info, questions, insights, and improvements. Please include "Teachers Tryscience" as your subject.

Thanks and hope you enjoy my lesson!