Objective: The purpose of this activity is to provide the students with an understanding
it takes a great deal of water to grow plants because they are primarily made up of
water. The learner will be able to:
1. Measure weight of slices of apples and potatoes before and after drying.
2. Observe and record the changes as the slices dry.
3. Compare the data before, during, and after drying of the slices.
4. Infer and describe the amount of water in food.
Materials: 5 apples sliced thinly, 5 potatoes sliced thinly, paper, pencils, scale
Background: Agriculture is a major user of our fresh water. Our food plants need a
great deal of water to grow. All living things contain much water. Green corn is 78%
water. For every pound of living plants cells it produces, a corn plant uses nearly 370
pounds of water. Potatoes are 78% water and apples are 80% water. The
predominance of water in apples or potatoes may be illustrated by weighing some
sections before and after setting them aside to dry.
This activity will require twenty minutes to set up on the first day, five minutes for
observation on day two, day three, day four and twenty minutes for observation and
closure on the last day.
Have students rub their fingers across the apple slice and the potato slice. Discuss what
they felt. Discuss what they observed on their fingers. Discuss with the students how
they would devise an experiment to observe the changes that occur when food is left to
Give each pair of students an apple slice and a potato slice. During this experiment, the
mass or weight of both slices should decrease and the outline of both slices should get
Lead the class through discussion to determine that the changes occurred because the
water in the apple and potato evaporated. Discuss the differences in beginning weight
or mass and ending weight or mass. Provide closure to the activity by discussing the
In groups of 2 students, create a food observation table with room to record the date,
outline of apple and potato slice, weight in grams, color, and texture for five days. Click
here for an example.
Weigh or determine the mass of the apple slice and the potato slice. Record the data
on the food observation table.
Place each slice on a sheet of white paper.
Draw an outline of each slice with your pencil. Label each slice.
Predict and record what you think will happen.
Weight, observe, and record the changes in appearance and outline each day for five
On the last day, eight or determine the mass of each slice. Record your data.
Follow Up Questions:
1. What caused the shape and size of the outline to change?
As the water dehydrated from the slices the outline became smaller.
2. How has the appearance changed?
The slices look dried and wrinkly.
3. How does it feel at the end compared with the start?
The slices feel hard and dry.
4. What part of the original slice was water?
Answers will vary; the lost weight is the same as water lost from the slice.
5. How could you remove the water more quickly?
Add heat to remove the water more quickly.
6. How does a dehydrator work?
It removes the moisture through the use of heat.
7. How can water be replaced once it is removed?
Soak the dried food in water to replace the moisture.
Have students bring in dehydrator from home and dehydrate various fruits and
Bring in dried fruit and record weight/mass, soak overnight, observe changes in size and
appearance, and find the new weight/mass.
Dehydrate the slices of salted and peppered meat in a low temperature oven to make
Encourage the students to compare different kinds of fruits and vegetables and rank
them by water content.
Mass: The quantity of matter in a substance
Weight: The measure of the heaviness of an object
Dehydrate: To remove water from
For Additional Information or Activities, Contact:
The Central Colorado Water Conservancy District
3209 W 28th Street
Greely, CO 80631
Reprinted with permission from the Central Colorado Water Conservancy District
SD Standards for 4th grade:
4.P.1.1; 4.P.1.2; 4.P.1.3; 4.E.1.1
Observing, Measuring, Inferring,
Numbering, Predicting, Hypothesizing,
Processing and Interpreting data,
Prior Preparation: Slice the apples
and potatoes into inch slices.
mass, weight, dehydrate