Changes in
Materials
Due to Oxygen
What do you observe in the
apple? Why do you think the
reason why apples turns to
brown color?
Life cannot exist without oxygen.
Fortunately on Earth, oxygen is the most
abundant element in the earth’s crust. The
atmosphere contains 21% free oxygen. As
people and animals breathe by taking in
oxygen, carbon dioxide is produced as a
waste product. Plants, in turn, utilize this
carbon dioxide, along with water, in the
photosynthesis of its own nutrient,
Aside from the beneficial effect
of oxygen to humans and
plants, there are changes and
end products that happen in
materials under the presence
or absence of oxygen.
When a container of coffee
granules or powdered chocolate
is left open for several hours, it
usually hardens. You will
enjoy eating French fries while
it’s hot but not after a few
minutes, it gets soft or soggy.
Do you know that
oxygen forms stable
chemical bonds with
almost all elements to
give the corresponding
Have you observed your mother
slicing an eggplant? What was the
color of the eggplant while it was
being sliced? What was its color
after a few minutes? Were there
any changes in the color? Did it
turn brown after slicing?
The changes in the color of the
inner fleshy part of the eggplant
is due to its exposure to oxygen.
The same phenomena could also
be observed in potato, banana,
guava, cassava, and other fruits
and vegetables.
How do you keep the eggplant from
turning brown?
Place in a large bowl of water with
a teaspoon of salt dissolved in it.
The water should be enough for all
the sliced eggplant to dip in fully.
This is to prevent the oxygen
present in the air to react with the
Another example of a change
in materials when oxygen is
present is in combustion. It
occurs when oxygen combines
with another substance (as
fuel) and produces fire with
Combustion is also known as
burning. It is always
exothermic, that is, giving off
heat. In combustion, oxygen,
fuel, and heat are always
present.
For example, when you lit
a candle, its wick burns if
oxygen and wax (candle)
is present and heat is
produced.
Other examples include the
burning of wood or charcoal for
cooking and burning of petrol
or diesel to run your car. If
oxygen is present in a wet
material with iron, such as a
nail or steel bar, the formation
It only happens when iron,
oxygen, and water react with
one another. Rust occurs
when iron or alloys such as
steel corrode, thus rusting is
commonly known as iron or
EXPERIMENT
TIME!
EXPERIMENT TIME!
A. Problem: How do fruits and
vegetables react in the presence of
oxygen?
B. Materials
>Potato
>A knife
>Air tight container/ container with lid
EXPERIMENT TIME!
C. Procedure
1. Ask for your teacher’s assistance to peel
the potato and cut it into two halves.
2. Put the first half of the potato inside an
airtight container.
3. Leave the other half on the table.
4. After 15 minutes observe what
happened to the potatoes.
EXPERIMENT TIME!
D. Observation
Record the changes that happened to
the potatoes. Write your observations
on the table.
Potato inside the
Potato that was left on
container
the table
E. Generalization: How do fruits and
vegetables react in the presence of
oxygen?
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Why is oxygen
important to living
organisms like us
human?
How does oxygen make
some metals change
color and become
rusty?
Directions: Write five (5) realizations/learnings you gain
with the experiment.
1.
2.
3.
4.
5.
Review:
Directions: Give at least five (5) changes that
happened to materials when exposed to
oxygen.
1.
2.
3.
4.
5.
Do you believe what is being
shown in the picture?
Why?