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Grade
Level: Elementary
| Time:
Activty
1 - one 20 min. period, with follow up 10 min observation
sessions, 30 min. wrap up; Activity 2 - two 30
minute periods
| Content Standard NSES Physical Science, properties of objects and materials | Ocean Literacy Principle 1f: The ocean is an integral part of the water cycle and is connected
to all of the earth's water reservoirs via evaporation and precipitation.
Big
Idea
Water
can "disappear" or evaporate into the
air.
Key
Concepts
-
Evaporation
occurs when a liquid is changed into a
gas.
- Rate of evaporation
increases when the temperature of a liquid
is increased.
- Water
moves around our planet in the water
cycle.
Essential
Questions
- How
does water change?
- How
does water move?
- How
does life depend on water?
- Where
does water go when it is evaporated?
Knowledge
and Skills
- Observe the process of evaporation or the
"disappearance of wetness
into the air."
- Compare and contrast their observations made before and after the
evaporation experiement.
- Construct a diagram of the experiment and use it explain
the results.
- Describe the process of evaporation, and the general water cycle,
through discussion and pictures.
Prior
Knowledge
- Some
events in nature have a repeating pattern - such
as daily weather patterns or changes in
temperature
and the appearance of rain and snow at different
times of the year.
- Water
can be a liquid, solid or gas and can go back and
forth from one form to the other.
Common
Preconceptions
- At the
elementary grades,
evaporation and condensation
will mean nothing
different from disappearance
and appearance.
- Students
have a difficult time
accepting the idea of invisible
particles of water in the
air.
- Students
understand the concept
of boiling and freezing
well before
understanding evaporation and condensation.
- When water
evaporates, it just
disappears and ceases to exist.
- When water
evaporates, it
immediately goes up to the clouds
or into the sun.
Concept
Map
Primarily for the teacher's use, the
map provided
here relates to the branch "Phases
of Water" from
the comprehensive Aquarius Concept Map - Water
& its patterns on Earth's surface.
From the comprehensive Aquarius Concept
Map: Water and its patterns on Earth's Surface.
Background
From the
US Geological Survey Water
website
Evaporation
is the process by which water changes
from a liquid
to a gas or vapor. Evaporation is the
primary pathway
that water moves from the liquid state
back into the
water cycle as atmospheric water vapor.
Studies have
shown that the oceans, seas, lakes, and
rivers provide
nearly 90 percent of the moisture in the
atmosphere
via evaporation, with the remaining 10
percent being
contributed by plant transpiration.
Evaporation
from the oceans is the primary mechanism
supporting
the surface-to-atmosphere portion of the
water cycle.
After all, the large surface area of the
oceans (over
70% of the Earth's surface is covered by
the oceans)
provides the opportunity for large-scale
evaporation
to occur. On a global scale, the amount of water
evaporating is about the same as the
amount of water
delivered to the Earth as
precipitation. This does
vary geographically, though. Evaporation is more
prevalent over the oceans than
precipitation, while
over the land, precipitation routinely
exceeds evaporation.
Most of the water that evaporates from the oceans
falls back into the oceans as precipitation. Only
about 10% of the water evaporated from the oceans
is transported over land and falls as
precipitation.
Once evaporated, a water molecule spends about 10
days in the air. The process of evaporation is so
great that without precipitation,
run-off, and groundwater
discharge from aquifers, oceans would
become nearly
empty.
Less
evaporation takes place during periods of
calm winds
than during windy times. When the air is
calm, evaporated
water tends to stay close to the water body. When
the winds are present, the more moist
air close to
the water body is moved away and replaced
with drier
air which favors additional evaporation.
Materials:
Activity 1. - containers with lids (coffee can
works well), water, wooden stirring sticks
(paint stirrers
work well), markers, colored sticky dots,
measuring cups;
optional materials include, construction paper,
glue
Activity
2. - salt, warm water (aids dissolving of
the salt),
paper, paint brushes, food coloring,
measuring cups,
containers (plastic cups work well and can
be reused),
spoons for mixing
Preparation:
Break students into working pairs for both
activities.
For Activity 2, pre-measure a 1/4 cup of salt
into one set
of containers for each student pair. Depending
on how many
colors you want each group to have you'll have
to calculate
how many containers and how much salt you'll
need.
Activity
1
- Show
students a coffee can half filled with water. Provide
the following instructions to the students:
"Each group
will receive two coffee cans that will each be
filled with
the same amount of water. You will cover one of the cans
and leave the other one open. Over the next few days
you'll watch the cans to find out what happens to the
water. Your job is to keep a journal that
shows the results
of what you see happening in each can. We
will talk about
what happens at the end of our study."
- Each
student pair should label their cans with
their names.
Mark each can with a colored dot.
- Show
the students the wooden stirrers. Ask the
students how
they could be used to test what happens to the water
level over time.
- Each
group/pair should use their measuring cup to fill
each can with the same amount of water.
- Have
students measure the water levels by dipping
their wooden
stirrers into the water at the side of the can until
it touches the bottom. They should make a
thin line on
their wooden stirrer at the water line (could be made
first with a pencil and then re-marked for visibility
with a marker). Mark the stirrers with
another colored
dot that matches the coffee can colored dot where the
measurement was taken.
- Place
the can in a safe area and instruct the
students to cover
one of the cans. Explain again that one of
the cans will
remain covered for the tests. They can uncover it to
take their measurements but then must
re-cover it when
they are finished.
- Students should check the cans on a regular basis (daily or every
other day) and record observations in their
journal. Based
on their observations, the students should draw
an illustration
in their journal that shows what is happening
to the water
in the cans over time.
- Extension - have each group glue its marked stir sticks to a piece
of construction paper. After the sticks have been glued,
students should label each of the lines for the days of
measurements that were taken. The students
should use this
graphic to help them answer and understand the questions
in the Assessment section.
Activity
2
- The
students will paint with saltwater paints and witness
evaporation taking special notice that only the water
evaporates and the colored salt is left
behind.
- In advance of the painting, discuss weather and the water
cycle. Use
a diagram of the water cycle to facilitate the
discussion.
Explain how energy (from the sun) warms the
water in bodies
of water like the oceans and lakes and the
water evaporates
into the air. The water vapor in the air condenses into
clouds. The clouds become filled with water and falls as
rain back into the oceans and on the land.
- Provide
the saltwater painting materials to each
group. Instruct
them to pour the salt into the warm water and gently
stir until the salt has dissolved. The
teacher will come
around to each group with the food coloring and help
the students add it to their saltwater mixtures. This
also allows the students to choose the
colors.
- Ask
the students to paint scenes that are related to the
water cycle using the colored, saltwater
mixtures.
- Lay
the paintings to dry overnight.
Assessment
Activity 1
-
- What happened to the level of the water in the closed
container?
- What happened to the level of the water in the open
container?
- Is there a difference in what we saw happen between the
two containers?
What is the difference?
- What did we do that was different with the containers?
- What if we used a different kind of container (e.g., jars instead
of cans)? Do you think the result would be
different?
Why or why not?
- Have
students draw the results of what they observed for each
of the containers. They should be prepared to share and
describe their drawings.
- Have
students share their pictures and describe the
results that
they saw for each of the studies. In both cases
of the open
container, what happened to the water in it?
What happened
to the water in the closed container? If you had a glass
of water that you wanted to save, should you
leave it open
or closed? Why?
- Ask
students to write and then share a brief response to the
following scenario. "It rained last night. You
notice a puddle in your yard the next morning and splash
around in it for a little while. Your mom tells
you to come
inside to get ready to go to the beach because
it is a warm,
sunny day. When you return in the afternoon to
play in the
puddle it has changed. What do you think will
have happened
to it? What if it wasn't a warm, sunny day and instead a
gray, cloudy day, how will that affect the puddle? Draw
a picture that illustrates what has happened.
"
Assessment
Activity 2
-
The following day, students will examine their paintings to find that the water
has evaporated but the colored salt remains.
- After
a group discussion about evaporation, have
the students
write a brief summary of what happened to
their painting.
Ask each student to explain how the process
of evaporation
relates to the scene depicted in his or her
painting.
- OPTIONAL:
If the range of scenes illustrated by the
group includes
rain, snow, clouds, a lake or ocean, then
conduct a gallery
walk of the students' artwork. As a group, categorize
the paintings by which part(s) of the water
cycle they
depict (i.e. precipitation, evaporation,
both).
Wrap
Up :
Re-engage the essential questions in a class
discussion for
review.
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