redox reactions, combustion, photography

1. THE ACTION OF COMMON
OXIDIZING AND REDUCING
SUBSTANCES IN EVERYDAY
ACTIVITIES

2. The process of corrosion forms yet another example of redox reactions in everyday
life. On contact with a metal, an iron and its alloy is exposed to oxygen atoms and
moisture/water the iron (or the metal) is oxidized by the oxygen to form hydrated iron
(III) oxide, Fe2O3 and free hydrogen ions. The iron (III) oxide is known as RUST. The
hydrogen ions generated combine with oxygen to yield water, and the whole cycle
begins once again. Given enough time and exposure the iron will completely oxidise.
Corrosion/Rus
ting

3. BLEACH
• A bleaching agent is a substance which has the
ability to whiten or decolourize other
substances. The process of bleaching also
employs a number of redox reactions.
• Decolourization of a substance occurs because
of the bleach containing sodium chlorate (I)
(NaClO). Oxygen bleaches contain hydrogen
peroxide (H2O2)
• Both bleaches the coloured dye/stain to their
colourless form
• ClO⁻ (aq) + coloured dye Cl⁻ (aq) + colourless dye
• Hydrogen peroxide, is also commonly used as an
antiseptic, is responsible for liberating oxygen;
which, in turn, oxidizes necrotic matter and
bacteria. Hydrogen peroxide helps in removal as
well as the loosening of the slough, ear wax,
acne etc.

4. THE BREATHALYZER TEST
• Cops often use breathalyzers or breath analyzers to estimate the content of
alcohol in a driver’s breath. Even the breathalyzers employ the chemical
principle of redox reactions.
• Once a driver breathes into the breathalyzers sample of orange potassium
chromate (VI) crystals (K2Cr2O7), What happens is that the ethanol in the breath
is oxidised , the dichromate orange-yellow ion (Cr2O7⁻) is reduced to
chromium(III)(Cr³⁺) which is green in colour. The amount of colour change
corresponds to levels of alcohol in the blood.
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5. BROWNING OF
FRUITS
• Oxidation reactions occur in food and non-food items. Enzymic
browning is a reaction which requires the action of enzymes and
oxidation in order to occur.
• What happens during enzymic browning?
• Oxygen in the air can cause sliced fruit to brown, a process called
enzymic browning (an oxidation reaction). Cells of the apple when
exposed to oxygen in the air, for example through slicing, the
oxygen causes a reaction. Chemicals in the fruits cells change
into melanin, which has a brown colour. You may have heard of
melanin before. Melanin is the pigment that gives human hair,
skin and eyes their colour.
• Why does enzymic browning happen?
• Foods are made up of lots of different molecules including some
called enzymes. Enzymes are special proteins which can speed up
chemical reactions and act as biological catalysts. They can cause
fruit to ripen and over-ripen, which gives the fruit a brown colour.
• Fresh fruit and vegetables normally keep enzymes trapped in their
tissues. However when the fruit is sliced, or squashed, or when
the fruit or vegetable begins to break down with age, the enzymes
come into contact with oxygen in the air. This causes the fruit to
turn brown.

6. FOOD PRESERVATION
• Sodium sulfites and suphur dioxide are typically added to processed foods to
prevent microbial spoilage and keep them from browning or changing color.
They do this by preventing oxidation.
• They enhance flavor, preserve freshness, prevent spoilage and discolouration of
foods such as wines, fruits, fruits juices, dried fruits, dried potatoes etc.
• The earliest known use of sulfites was in the treatment of wines with sulphur
dioxide by the Romans.
• Sulfites are sprayed on fresh foods such as shrimp, fruits, and vegetables. They
are also used as antioxidants and preservatives in many pharmaceuticals.

7. RESPIRATION
Cellular respiration which is the ultimate source of energy in human beings
encompasses a series of redox reactions. So, the food that we consume is
converted into energy by redox reactions only.
During the process of respiration, the carbon-dioxide is reduced whereas the
water is oxidised to form oxygen.

8. COMBUSTION
• Combustion forms the classic example of
redox reactions in real-life.
• However, whenever we talk about combustion,
we usually view it as a physical change than a
chemical one. The burning of organic material
and combustion of hydrocarbons in fossil
fuels form yet another important example of
redox reactions.
• The oxygen present in the atmosphere bonds
with carbon and hydrogen present in the
compound being burned. During the process
of combustion, the oxygen present in the
atmosphere is being reduced whereas the
compound which is being burned is
undergoing oxidation.

9. PHOTOSYNTHESIS
The process of photosynthesis
takes place in the leaves of the
plants. What happens is that
carbon dioxide and water combine
in the presence of sunlight to
release oxygen and glucose. The
glucose which is formed in the
whole process of photosynthesis
is used to fuel the metabolic
reactions of the plants. In
photosynthesis, water is oxidised
and carbon dioxide is reduced.

10. PHOTOGRAPHY
• The process of developing a photographic film also employs redox reactions.
The silver ions in activated silver bromide are reduced to silver atoms by
reducing
• in addition, sodium thiosulfate is also used in the process of obtaining a
negative. A positive image is obtained by the exposure of the negative to light.
Following the exposure to light, silver cations are reduced.

11. REFERENCES
• HTTPS://WWW.YOUTUBE.COM/WATCH?V=RVVZLG26BCM
• HTTPS://STUDIOUSGUY.COM/EXAMPLES-REDOX-REACTIONS-EVERYDAY-LIFE/
• TINDALE, RITCHIE ET AL, 2014, CHEMISTRY FOR CSEC 2ND EDITION, NELSON
THORNES. CHAPTER 9, P156-157
• HTTPS://WWW.IFST.ORG/LOVEFOODLOVESCIENCE/RESOURCES/FRUIT-AND-
VEGETABLES-ENZYMIC-BROWNING