Density/ Floating and Sinking! external image wn_float_candle_sm.jpg



*This is what one of the boats made is class looked like. Description of Lesson- Materials Needed: · Clay (enough for each pair to have a large ball) · At least 3 tubs to hold the water set up in different centers around the room · 100 marbles (you want to be sure that you have several at each station) · Paper Towel · Science Journal · Pencil
Engage- Before beginning the lesson, preform the science demonstration listed below. This demonstration is called Bubbling Lava Lamps and it will help to introduce density to the students. It was will show what happens when an Alka-Seltzer tablet is added to oil and water. The concept of density is seen when the oil and water do not mix. After doing the demonstration, introduce the children read to book " Who sank the boat" by Pamela Allen. This is a great book to get the children thinking because it is the little mouse at the end who sinks the boat; not the bigger animals who you think would. You will need to make sure the children have basic knowledge of what sinking looks like and what floating looks like.This may seem stupid but some children have a problem with this. Here is an example of what I am talking about : if you have an object that is at the top of the water we know it is floating, if you have one that the bottom you know that it sank. But, what if you have an object that is sitting in the middle of the water? Some children think that since its not on top of the water it is sinking but really it is floating. Explore- You would give each pair of students a ball of clay and ask them to make any "boat" shape that they think will float and hold the most marbles or coins. You will could have three different centers set up for the children to test how their boat works so it will be more time efficient. Ask the children to see how many marbles their boat can hold before it cap-sizes then have the children go back to their seats, draw their model and how many marbles it held. Explain- Density- a measure of how closely packed the molecules are Density Formula- mass/volume The reason the clay boat floats is because the molecules in the clay are not packed as closely therefore the boat is less dense than water allowing it to float. If the density is greater than water it will sink. You could also incorporate math into the lesson by having them calculate the density of an object. Make sure to tell them that if they only have the mass and the volume they can figure out how dense and object is by using the formula.

Expand- Have them re-work their clay, and with the information they got from their first try, make a boat that will float longer and hold more marbles. Once, they have tried that at least three times and have drawings and predictions for each one, have them go back to their seat so that you can discuss what is going on. Evaulate- Have the children solve a few problems finding the density of an object.Then you could have them complete a worksheet with drawings of different shapes of boats and their density. This worksheet would be able to tell if the children understood the concept of density.

Science Content:
Students will need to understand the scientific method:
a. Investigation, prediction, carrying out the experiment, observation and conclusion.

Important definitions before starting:
Density: How closely packed the molecules are. (Example: A great way to explain density to kids is to use the terms "packed together" and "less packed together." -- "packed together"

less dense, and "less packed toegether"

more dense.)
Volume: The amount of space an object takes up
Weight: The quantity of an object
Floating: Being buoyed in water
Sinking: Partially submerged in water
Prediction: Foreshadowing about a particular event

Teacher Notes!!
*The students need to understand that an object where the density is less then the water will float. An object where the density is more then the water, the object will sink.*

Major Misconceptions About Floating & Demonstrations to Dispute Them:
#1 - Things float because there is air inside - Drop an apple in water
#2 - Things float because they're light - Drop a grape and a grapefruit in water
#3 - Things float because of their large surface area - Drop a pancake of clay in water

LESS dense objects (things that are less packed together) float on top of things that are MORE dense (more packed together); this includes things other than liquids such as gases and circumstances like a cheese doodle in rice. As long as an object is less dense than the substance it is in, it will float. If an object is too dense it will sink to the bottom.
*LARGE, light(less dense) object will FLOAT.
***Small, heavy (more dense) objects will sink.

?Questions we still have?: (if you know the answer, feel free to add to our page!!)

Can we change something from a sinker to a floater?

Can we change an object that is floating to sink?

Does the formula, Density= mass divided by volume have to do with this particular experiment. If so, how?

How many more marbles can our boats hold if we had more that day?

North Carolina Standard Course of Study Connection: Children's Literature Books All books were found under a search on · Who Sank the Boat by Pamela Allen · The Magic School Bus Ups and Downs: A Book about Floating and Sinking by Joanna Cole and Illustrated by Buce Degan · Floating and Sinking First Facts: Our Physical World by Ellen Sturn Niz · Float and Sinking Science All Around Me by Karen Bryant- Mole · The Floating Island (The Lost Journals of Ven Polyphme) by Elixabeth Haydon · The Sinking of the USS Indianapolis by Marc Tyler Nobleman · The Sinking of the Titanic by Matt Doeden, Charles, III Barnet, and Phil Miller · The Story of the Sinking of the Battleship Maine by Zachary Kent · The Floating House by Scott Russell Sanders · Captain Noah and his Floating Zoo by Michael Flanders · The Floating Orchard by Troon Harrison and Miranda Jones · George and Matlida Mouse and the Floating School by Heather S. Buchanan

Science Demonstration
Purpose and Target Concepts:
We all know that water and oil do not mix. This is because the two different kinds of molecules do not mix together. The food coloring only mixed with the water for the same reason. When the water was added to the oil, in this demo, the water sank immediately to the bottom of the bottle. This shows us that water is heavier than oil. This also tells us that water has a greater density than oil. This shows what oil spills are like in the ocean. If an oil rig explodes or an oil ship wrecks, the oil pours out and floats on top of the ocean. This can be a good and bad thing. The oil is easily seen on the ocean’s surface.
When the Alka Seltzer pieces were added to water, tiny bubbles of carbon dioxide were produced. These bubbles connected with the colored water and floated to the top of bottle. At this point, the colored water was on top of the oil, but only for a short time. Once they bubbles popped, the colored water floated back to the bottom of the bottle, below the oil.

  • Soda bottle (16 oz.)
  • Vegetable Oil (the cheaper the better)
  • Food coloring
  • An Alka Seltzer tablet
  • Water

1) Fill bottle ¾ full with the vegetable oil.
2) Fill rest of bottle with water (almost to the top, but do not overflow)
3) Add about 10 drops of food coloring, so the water is fairly dark.
4) Break the Alka Seltzer tablet into eight pieces.
5) Drop one piece of Alka Seltzer into the bottle. Once bubbling has stopped, add another piece of Alka Seltzer. Do this until all of the pieces have been added.
6) Once all the pieces have been added and bubbling has stopped, put cap back on bottle.
7) Turn the bottle back and forth forming a wave effect.
8) Droplets will form to cause a “lava-like” blob.

Questions to Ask:
· (right before adding water to oil) “What do you think will happen when the water is added?”
· (before adding the food coloring) “What will happen when the food coloring is added?”
· (before adding Alka Seltzer/ while breaking up Alka Seltzer) “Has anyone dropped Alka Seltzer in any liquid?” If so, “What happened?”
· “How will the tablets affect the oil, water, and food coloring?” “Will it make the liquids, in the bottle, overflow?”
· “What will happen if we shake the bottle up?”
· “What makes all the small particles form together?”
· (after demo) “Why doesn’t the water mix with the oil?”
· “Can you think of a way this might affect our environment?”

Spangler, S (2007). Science Experiments. Retrieved September 23, 2007, from Steve Spangler Science Web site:

Online Resources

Density Lesson Plan-
Floating and Sinking Kit- Kid's Research Center-
Activity- Interdisciplinary Resources Science Human Body- Social Studies History of Titanic Population- Math Take percentage of objects that floated Write the fractions of the amount of objects that sank Graph results of activites English Language Arts Writing a paragraph using similies of how an object floated Interview a naval person Write a paragraph explaining why an object sank and floated Writing- external image logotransp.gif