Student's Pages
Activity 10: " Counting Calories-Measuring Food Energy"
ACTIVITY 10 -TEACHER'S PAGE
Is "plant food" you buy at the store and other minerals
and fertilizers food for plants?
Van Helmont found that soil is not food for plants. But what
about that stuff we put in the soil? Have you ever seen "Plant Food" or fertilizer you can buy at the
store to give to your plants? It is called "food", so
is that providing food energy for the plants?
Today we will consider the hypothesis:
HYPOTHESIS: Plant food or minerals and fertilizers are food for
plants.
EVIDENCE: Can we find any evidence to support this hypothesis?
Can we find any evidence to challenge this hypothesis?
Are vitamins or minerals food for plants?
Is "plant food" you buy at the store food for plants?
What do YOU think?
I think minerals and plant food people give to plants ARE or ARE
NOT providing food energy for plants because_______________________________________
_____________________________________________________________
_____________________________________________________________
Measuring Energy in Foods: Calories
Scientists can measure how much food energy is in different
foods. They measure how much food energy is in a food by using a unit called a calorie. A food with
a lot of calories has a lot of food energy in it. Foods with very few calories do not have as much food
energy in them. Materials that contain no calories do not contain any food energy. Water is an example of a
material that contains no calories.
Water does not give you any food energy.
How do scientists find out if there are calories in a substance?:
One way to find out if something has food energy is to burn it.
Do not try this at home! If something is a food, then it should burn. Scientists burn various foods and measure
how many calories are in them. Then this information can be put on our food containers, so we know how
many calories are in the food we are eating.
Watch your teacher try to burn a peanut.
Do you think the peanut will burn? _______
Why? ____________________________________________________________
The food energy in the peanut was what burned. The black ashes
are the minerals that were in the peanut. If you would have eaten the peanut, those minerals would have become
part of your body, and the energy would have been used up or stored as fat.
Name ___________________________
Are vitamins or minerals food for plants?
Is "plant food" you buy at the store food for plants?
Predictions
1. After our research work today, your teacher will try to burn a
sugar-free vitamin pill.
Do you think the vitamin pill will burn? _______
Why? __________________________________________________________
2. Your teacher will also try to burn a plant food stick
(minerals).
Do you think the plant food fertilizer stick will burn? _________
Why ? __________________________________________________________
How to Explore Labels:
You will look at labels to find out if the materials contain
energy as measured by calories. If the material has calories, then you know it is an energy-providing food. If the
material does not contain calories, then it is not an energy-providing food.
Each label will tell you the ingredients that are in the package.
It will list the different ingredients, the vitamins, the minerals, and the calories (if there are any).
Look at the calorie content of different materials to find out if
they have any food energy in them. Also look to see if the substance contains any kind of sugar (glucose,
fructose, sucrose), because sugar is energy-containing material.
Examine as many items as you have time for.
Write your results on this chart:
Name (s) ________________________
Which Items Contain Food Energy?
NAME OF "FOOD"
Does it contain any calories? If yes, how many?
Does it contain any sugar (glucose, sucrose, fructose)?
Does it contain any food energy?
Is it a "food" using the scientific definition of food?
Why or why not?
Name ________________________
REFLECT AND CONNECT:
Are minerals and fertilizers food for plants?
Look at Your Chart...
1. Which items on your chart are NOT food by the scientific
definition?
_________________________________________________________________
_________________________________________________________________
2. Do you predict that the vitamin pill will burn? __________
Watch what happens when your teacher burns the vitamin pill.
How do you explain the
results?_________________________________________
_________________________________________________________________
3. Do you predict the "plant food" sticks will burn?
___________
Watch what happens when your teacher burns the plant food sticks.
How do you explain the results?
_________________________________________
__________________________________________________________________
4. Write on a yellow post-it your evidence to support or
challenge the hypothesis that minerals and plant food are food for plants. Put your post-it in the appropriate
column on your class data chart.
5. Draw a picture of something you learned today:
REFLECT AND CONNECT:
The Grass Experiment and Von Helmont's Experiment and Our Food
Analysis Project
What observations did Van Helmont make in his experiment back in
1642?
What observations did you make of the grass plants in the light
and the dark?
What observations did you make about plant "food" and
minerals from your study of their energy calories?
Let's try to put these three experiments together and see what we
can figure out about how plants get their food.
When the grass seeds first began to grow, they used food stored
in the ______________ for their energy.
As the plants got bigger, the food in the cotyledons was all used
up. Now what could the grass plants use for food energy?
Could they use soil? We know from Von Helmont's experiment that
soil is not food for plants. It did not get used by Von Helmont's tree as it grew. Soil does not supply food
energy for plants.
Could the grass plants use minerals in the soil for food energy?
We know from our calorie experiment that plant foods and minerals do not contain any calories, so we know
they do not provide living things with any food energy. So the grass plants could not get energy from the
minerals or fertilizers in the soil.
Could the grass plants use water for food? In the grass plant
experiment the grass in the light and the grass in the dark had the same soil and the same amount of water. Both
had soil and water, but the plants in the light lived and the plants in the dark died. The plants in the
dark died even though they had water. Also, our calorie count showed that water has no calories -- no food
energy. So water could not be food for plants.
Just like people, plants cannot use water for energy. You would
starve to death if you only drank water and ate no food. You would not be getting any food energy because
water does not have any food energy. Plants starve to death, too, if they do not get their food. And water by
itself is not food for plants.
The reason the plants in the dark died is that they did not have
food to give them energy to continue living and growing. The soil and the water were not enough. The plants
in the dark had water and soil, but they had no food for energy. They died from lack of food.
WHAT DO YOU THINK?
Are you convinced that water is not food for plants? Why or why
not? ___________
________________________________________________________________
________________________________________________________________
Are you convinced that soil is not food for plants? Why or why
not?____________
________________________________________________________________
________________________________________________________________
Are you convinced that minerals in the soil is not food for
plants? Why or why not?
_________________________________________________________________
_________________________________________________________________