9-11
years
Science Content:
Physical Science
Target Concepts/Skills:
Density and Bouyancy
Target Age group: 9-11 years
Duration of activity: 3 hours
Summary: In this activity children inquire about why some
objects float and others do not, relating this
phenomenon to the overall density of the body.
Situations presented include high-mass objects
that can float, like a large ship of iron, but simultaneously low-mass objects unable to float, like a
small iron nail (experiment 1). In other situations
presented there are large and small objects and
some of each can float while others cannot (experiment 2). The inquiry leads children to learn
about the principal property which determines
whether or not a body floats is its density that is
calculated dividing the weight of the body by the
volume it occupies (experiment 3 and 4).
Objective:
By the end of the activity children should be able to:
•
Indicate that there is no direct relationship
between the buoyancy of an object and its
mass;
•
Indicate that there is no direct relationship
between the buoyancy of an object and its
volume;
•
Determine the ratio between the mass and
volume of different objects.
•
Verify that the buoyancy of the object
depends on its density and on the liquid’s
density.
Resources:
•
Tank with water.
•
Several objects with different masses and
sizes.
•
Kitchen scale.
•
Three Legos® boxes with different sizes
and masses
•
Graduated ruler
•
Large beaker of 1000 ml.
•
Graduated cylinder of 500 ml.
•
Rubber balloon.
Water, Icebergs
and Boats
Authors: Mário Rui da Cunha Pereira, Hands on Science
The content of the present document only reflects the author’s views and the European Union is not liable for any use that may be made of the information therein.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Lesson plan (with inclusion of teacher notes)
Description of activity
The teacher divides the children into groups of three, asking
them to bring from home objects of different sizes and weights
that can get wet and some float while others sink.
Experiment 1: Floating - Light or heavy objects
Provide to each group a tank with water and a scales. Three
objects are chosen for the experiment. After weighing pose
the question: which ones do you think will float and which ones
will sink? Ask the children to place the objects in the tank with
water. Get them to record the behaviour of each object and
discuss the differences from what they had predicted.
Experiment 2: Floating - Large or small objects
Using again three of the objects collected at home of different
volumes, began by questioning the students about which
bodies they think will float. The objects are then placed in the
tank filled with water and the differences between the size of
the bodies and the fact that some float while others don’t is
discussed. Children are asked to give examples of large and
small objects with different floating behaviours.
Experiment 3: Floating - Density
Now each group will have three closed boxes filled with Legos
®, having different sizes and masses. Begin by measuring the
dimensions of each box and its weight. The volume of each
box is determined. Then measure the volume of water equal
to each of the boxes and its weight is recorded. Students
are asked about which of the boxes they think will float and
which will sink. The boxes are placed one by one in water and
record which float and which sink. For each case the ratio
between mass and volume, density, is calculated and the same
calculation is made for the different water volumes. Students
are questioned if with the values obtained they could predict
which ones would float.
Experiment 4: Quiz - Will they float?
Students are challenged to test with one of the objects
collected from home if it will float or sink, using the previous
conclusions made. This requires a tank, a beaker which fits
the object and a graduated cylinder. They start by measuring
the mass of the object, using the scale, and the volume, by
the volume of the spilled liquid from the filled beaker to the
tank when the object is completely submerged. Compare the
density of the body with the density of water and verify that its
behaviour is in agreement with expectations. Students are also
asked what would happen if an object has a density equal to
water. Fill a rubber balloon with water and place it in the water.
Students comment what they observe
1. Engage (Forming hypotheses)
Stimulus: Children are asked what happens when an object is
placed in water.
Pose the questions: Why do some bodies float and others sink?
•
•
•
•
Does the mass of the body determine if a body floats?
Does the volume of a body determine if a body floats?
Could it be another property of the body?
Can we predict if a body floats or sinks based on its
properties?
2. Inquiry (Designing and running experiments and observations)
Investigation: How can we find out what makes a body
float or sink?
In order to answer the questions previously set ask the
children to plan experiments to test the different hypotheses
using bodies with:
1.
2.
Different mass;
Different volume.
The teacher explains how to use a table to organize the
collected data.
The children conduct a new experiment to determine a
property of the bodies that relates its mass and volume.
1.
2.
They measure mass and volume of different bodies;
They measure mass and volume for different water
samples.
Finally ask the children to plan an experiment to discover if a
body should float or sink.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
3. Evaluation (Evaluating evidence)
Evaluation, explanation of findings
Results are presented to all class by group leaders. Using the
collected data, students must come to the evidence that:
• the mass or the volume of a body, alone, does it determine
if a body floats or sinks;
• the ratio between the mass and the volume is constant
for the water;
• only bodies with density lower than the water will float in
water;
• and if they know the overall density of a body they can
predict if it will float or sink when put in the water.
Extended thinking: What happens if a body has the same
density as water is dropped in water? What happens when we
transform the liquid water to ice? And what happens if instead
of water we have another liquid, like oil?
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Teacher Notes
Experiment 1: Floating - Light or heavy objects
To each group is delivered a tank with water and a scale. Three
objects are chosen for the experiment. After weighing pose the
question: which ones the students think will float and which
ones they think will sink. The objects are then placed in the tank
with water. Record the behaviour of each body and discuss the
differences from what was anticipated.
Experiment 2: Floating - Large or small objects
Using again three of the objects collected at home with different
volumes, we began by questioning the students about which
bodies they think will float. The objects are then placed in the
tank filled with water and the differences between the size of the
bodies and the fact that same float while others don’t is discussed.
Children are asked to give examples of large and small objects
with different floating behaviours.
Experiment 3: Floating - Density
Now each group will have three closed boxes made with Legos
®, with different sizes and masses. Begin by measuring the
dimensions of each box and its weight. The volume of each box
is determined. Then measure a volume of water equal to each of
the boxes and its weight is recorded. Students are asked about
which of the boxes they think will float and which will sink. The
boxes are placed one by one in water and record which float and
which sink. For each case the ratio between mass and volume,
density, is calculated and the same calculation is made for the
different water volumes. Students are questioned if with the
values obtained they could predict which ones would float.
Experiment 4: Quiz - Will they float?
Students are challenged to test with one of the objects collected
from home the previous conclusion. This requires a tank, a
beaker which fits the object and a graduated cylinder. They start
by measuring the mass of the object, using the scale, and the
volume, by the volume of the spilled liquid from the filled beaker
to the tank when the object is completely submerged. Compare
the density of the body with the density of water and verify that
its behaviour is in agreement with expectations. Students are also
asked what would happen if an object have a density equal to
water. Fill a rubber balloon with water and place it in the water.
Students comment what they observe.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Experiment 1: Floating - Light or Heavy Objects
Topic:
Buoyancy and Mass
Concept:
The body mass alone does not determine if it floats or sinks.
Problem:
What determines whether a body floats the sink?
Introduction
You have probably already observed the behaviour of various
objects when placed in water, some float while others sink. If we
try to land a stone in the water of a lake, no matter how careful
we are, it will immediately sink. But if we do the same with a piece
of wood, no matter how high we let him fall, it insists on keeping
close to the surface, floating. If we reduce the size of the stone it
will continue to sink while the wood will continue to fluctuate even
if it has the size of a tree. What properties determine whether an
object floats or sinks?
Material
• Several objects collected by the students with different
masses and densities.
• A large tank with water.
• A kitchen scale.
Experience Implementation
1. Children are divided into groups of three. Each group is given
a tank with water.
2. The children are asked to place three of the collected objects,
one at a time, in the balance and record its mass.
3. The objects are place in the tank with water and children
record which ones float and which sink.
Experience Guidance
Previously the teacher should ask students to collect various
objects for the experiments with different masses and densities,
taking care to state its maximum size according to the tubs and
selecting objects that can get wet.
Before the beginning, the teacher should help to select objects
for this experiment with similar dimensions and in which there is
at least one that floats and one that sinks. After all objects have
been weighed the teacher can ask:
- Which objects you think will float?
Throughout this experience the students should be able
to realize that:
- There are massive bodies that float and while others sink and the
same happen with the lightest.
- It is not the body mass alone that determines whether or not an
object floats.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Student Sheet
1. Preparing the experience
Which bodies are able to float?
Does the mass of a body determine whether it floats or sinks?
What will you need?
1. A large tank with water.
2. Several objects with different masses.
3. A kitchen scale.
What do we want to discover from this experience
When we place a light object in water it:
Floats.
Sinks.
Depends on the size.
2. Now let’s make the experience
How do we do it?
1.
2.
Place the water tank carefully on the table.
Using the kitchen scale, weight each of the objects selected
for the experiment.
3. Place all objects, one by one, in the water.
4. Register which objects float and which sink.
What do we observe?
1
When we place the objects in the water:
They all sink.
They all float.
Some sink while others float.
2.
When comparing with each body’s mass we can conclude that:
The heaviest sink.
The lightest sink.
Do not depend only on the mass
(some lighter sink and some heavier float).
3.
After the experience
What have you learned from this experience?
(you can tick more than one answer)
All heavy bodies sink.
The ability of a body to float does not depend only on its mass.
For a body to float is not enough to be lightweight.
All light bodies float.
Go back and check if your answers were correct.
They were all right
They were all wrong
Some were right and some were wrong
When we place an heavy object in water it:
Floats.
Sinks.
Depends on the size.
Why do you think that?
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Experience 3: Floating - Density
Teacher’s Notes
Topic: Buoyancy and Density
Concept: For an object to float the ratio between its mass and
the volume it occupies should be less than the one of the liquid.
Problem: What determines whether a body floats the sink?
Introduction
You have probably already observed the behaviour of various
objects when placed in water, some float while others sink. If we
try to land a stone in the water of a lake, no matter how careful
we are, it will immediately sink. But if we do the same with a piece
of wood, no matter how high we let him fall, it insists on keeping
close to the surface, floating. If we reduce the size of the stone it
will continue to sink while the wood will continue to fluctuate even
if it has the size of a tree. What properties determine whether an
object floats or sinks?
Materials
• Three boxes, built with Legos ® with different sizes and
masses.
• A large tank with water.
• A kitchen scale
• A graduated ruler
• A large beaker of 1000 ml.
• A 500 ml graduated cylinder.
Experience Implementation
1. Each group will have a set of three boxes and begin by
determining their size by measuring the length of its edges.
Record values and calculate the volume of each box.
2. Using the kitchen scale, weight each box and register the
obtained values.
3. Next, weight in the graduated cylinder volumes of water
equal to each box.
4. The boxes are placed in the water tank and students observe
and register its behaviour.
5. Students try different mathematical relations between the
mass and the volume for each box and for the different
water volumes in order to find the appropriated property.
6. Students compare the obtained values for the boxes densities
with what they observed in terms of its ability to float.
Experience Guidance
The teacher can use this experience to instruct the students about
the construction of tables as a way to record data (in this case, on
one column the list of boxes followed by their mass, volume, mass
of an equal volume of water, prediction of whether they float or
not, what they observed when put in water and the calculations of
the possible relations between the two quantities).
After the measuring and weighing phase of the boxes the
teacher should ask:
• How will each box behave? Why?
When calculating the mathematical relation between mas and
volume teachers should stress the fact that they search for
a relation that should always give the same value for the same
material highlighting the character of a material property. At the
end students should be questioned about their ability to predict if
a body will float or not without loading it into the water.
Throughout this experience the students should be able
to realize that:
- The density is a property of materials and is defined as the ratio
between the mass of a body and its volume.
- It’s the overall density of a body that determines if, when putted
in water, it will float or sink.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Student Sheet
1. Preparing the experience
• Which bodies are able to float?
• What property of the materials allows us to predict whether
they float or sink?
4. Calculate different mathematical relations between the mass
and the volume for each box and for each water volumes.
5. Place, one by one, all boxes in the water and register which
floats and which not.
What will you need?
1. Three Legos® boxes with different sizes and masses
2. One kitchen scale
3. One graduated ruler
4. One tank with water.
What do we observe?
1 – The mass and the volume of a material can define a property
when we?
Divide the volume by the mass.
Divide the mass by the volume.
Multiply the mass by the volume
Add the mass to the volume
What do we want to discover from this experience?
Size Floating better Colour Liking better determine Mass Smelling better Have wheels Seeing better To determine if a body will float or sink we need to know:
Only its mass
Only its volume
Its mass and volume
Its colour
Why do you think that?
2. Now let’s make the experience
How Do We Do It?
1. Place the water tank carefully on the table.
2. Using the graduated ruler, measure the edges for each
selected box and calculate its volume. Record on a table the
obtained values.
3. Using the kitchen scale, weight each of the boxes and register
the values.
2–
When weighted all water volumes:
weighted the same;
the bigger the volume the bigger the mass;
the bigger the volume the smaller the mass.
3–
For the water, the ratio between the mass and the volume was:
always the same;
changing with water volume;
changing with water mass.
4 – When we compare the densities of the boxes
with its floatability we conclude that:
the ones with density higher than the water sink;
the ones with density lower than the water sink;
if they float or not does not depend on the density.
3. After the experience
What have you learned from this experience? (you can
tick more than one answer)
Objects more dense than water will sink
Objects less dense than water will sink
We call density to the ratio between the mass and the
volume of a body
The density is a body property.
Go back to the page 27, and check if your answer was
correct.
Yes, it was
No, it wasn’t
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Experience 4: Quiz – Will They Float?
Teacher’s Notes
Topic:
Buoyancy and Density
Concept: For an object to float its density have to be lower than the one
of the liquid.
Problem: Can we predict if a body will float or sink before putting
it in the water?
Introduction
You have probably already observed the behaviour of various
objects when placed in water, some float while others sink. If we
try to land a stone in the water of a lake, no matter how careful
we are, it will immediately sink. But if we do the same with a piece
of wood, no matter how high we let him fall, it insists on keeping
close to the surface, floating. If we reduce the size of the stone it
will continue to sink while the wood will continue to fluctuate even
if it has the size of a tree. What properties determine whether an
object floats or sinks?
Materials
• One object collected by the students.
• A large tank with water.
• A kitchen scale
• A graduated ruler
• A large beaker of 1000 ml.
• A 500 ml graduated cylinder.
• A rubber balloon.
Experience Implementation
Each group will star by choosing one object for the experiment.
1. Using the kitchen scale, weight the object and register the
obtained value.
2. Next they submerge completely the body in a beaker full to
the top of water. The beaker should be placed previously
inside the tank to collect the spilling water. If the body floats,
one should be careful when submerging the body to not
touch the water with their hands. Register also at this point if
the body floats or not.
3. Collect the spilling water measuring its volume with the
graduated cylinder.
4. Compute the ratio between the obtained mass and volume
for the object.
5. Verify if the determined density is in agreement with the
observation concerning the floatability of the object.
Experience Guidance
At the beginning teacher should ask:
• What do we need to measure to predict if a body will float or
sink when placed on water?
Submerging the body for measuring its volume will only be
efficient with objects which do not absorb water and if made in a
way that only the volume of the object is responsible for spilling
the water from the full beaker. So, particular attention must be
placed on volume determination especially if the body floats. The
teacher must instruct students about these facts and tell them
how to proceed.
After the measurements take place, teacher must ask:
What value for the density one must obtain for an object to float?
At the end he can question students about two things:
• What they think it would happen if the density of the body
was equal to the one of the water. In this stage he can fill a
rubber balloon with water, carefully take out all air and close
it with a knot, put it in the water and discuss with the class
what they observe.
• Why the icebergs float if they are made of the same water
of the ocean? Can they plan an experiment to discover why?
Throughout This Experience The Students Should Be Able
To Realize That:
• The determination of the density of a body allows us to
preview if it floats or sinks when placed on water.
• A body with density equal to the water will not floats or sinks;
it will remain stationary inside the water.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
Student Sheet
1. Preparing the experience
• Can we predict if a body will float or sink when placed in
water?
What will you need?
1. One object collected by the students.
2. A large tank with water.
3. A kitchen scale
4. A graduated ruler
5. A large beaker of 1000 ml.
6. A 500 ml graduated cylinder.
7. A rubber balloon.
Earing Size Colour affect Sinking Density Smelling Have wheels Seeing When placed on water which objects floats better?
The red objects
The objects less dense than water
The objects with density equal to the water
2. Now let’s make the experience
How Do We Do It?
1. Place the water tank carefully on the table with the beaker
full of water inside at its center.
2. Using the kitchen scale, weight the selected object and
register the value.
3. Carefully submerge the object without touching the water.
4. Determine the object’s volume by measuring with the
graduate cylinder the spilled water. Register the value and
indicate if the body floats or sinks.
5. Compute the object density dividing the obtained mass by
the measured volume.
What do we observe?
When placed in water the object?
Sink.
Floated.
2 – Comparing the density of the object with the water we see
that:
The object is denser than water and it sinks.
The object is less dense than water and it floats.
The object is denser than water and it floats.
3 – When the body with density equal to the water was placed in
water it:
Sink.
Floated
Neither sink nor float, just stayed in the middle of the water.
Why do you think that?
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647
Water, Icebergs
and Boats
3. After the experience
What have you learned from this experience?
(you can tick more than one answer)
We can measure o body’s volume trough the water spilled
from a full glass
We cannot predict which bodies will float and which will sink
Knowing the density of a body we can anticipate its floatability
Bodies with density equal to the water don’t sinks or floats,
just stay inside the liquid.
Go back to the page 34, and check if your answer was
correct.
Yes, it was
No, it wasn’t
Finally think - if icebergs are made of the same water of
the oceans why do they float?
The mass of the frozen water is lower than the liquid water
resulting in a lower density
The volume of the frozen water is bigger than the liquid
water resulting in lower density
The icebergs are not made of water
Plan an experiment to verify if your answer is correct.
This project Pri-Sci-Net has received funding from the European Union Seventh
Framework Programme (FP7 2007 /13) under grant agreement No.266647