Chemistry in Our Everyday Life

Chemistry in Our Everyday Life

Pls complete introduction.

The Tearjerking Vegetable

Onions – the vegetable that causes inevitable tears when you slice them open. We all know they makes our tears fall, but we never really know why. What is it that makes our eyes burn? Well, you can put the blame on chemistry.

When an onion is cut, it’s cell structure breaks, allowing it’s contents, including amino acids sulfoxide, to be released. This produces a compound called sulfenic acid. The sulfenic acid reacts with the enzyme lachrymatory-factor synthase forming syn-propanethial S-oxide (C3H6OS). This chemical rises and reacts with the tears that are already present in the eye forming sulfuric acid – the acid used for batteries! This triggers the tearing and stinging sensation.

There are 3 types of tears:

  1. Emotional tears – when we are sad
  2. Basal tears – keeps our eyes lubricated, thus constantly replenished
  3. Reflexive tears – to wash away irritants

The eyes are equipped with sensory nerves that protects the eye from physical and chemical irritants. It sends the signal to the central nerve system that can feel the burning sensation. Then the signal is carried to the lacrimal glands that releases the tears to wash the irritant away.

Here are some advice/ tips to cutting onions:

  1.  Wear goggles
  2. Use a ventilator or fan to blow the chemical away
  3. Use a sharp knife to prevent a worser damage to the cell structure
  4. Refrigerate before cutting to reduce the tendency of the onions releasing volatile compounds that turn to gas

Pan Rust (Rust + Coke)

If you procrastinate at every aspect of life, chances are, you have left your skillet in the sink after cooking. That is if you even cook. The worst part is not bearing to scrub the skillet with a brillo pad for like, an eternity. Fortunately, there is a way to make your job easier – with the use of Coke.

Coke consist of a chemical called phosphoric acid that contributes to the sour taste in the super sweet soft drink. Phosphoric acid (or hydrochloric acid – an alternative) is commonly used to remove rust and tarnish from metal as it dissolves rust a much faster speed than it dissolves iron. Phosphoric acid has a pH value of 2.8. It can dissolve a nail in 4 days! The acid reacts with the ferric oxide (rust) to form ferric phosphate and water. The chemical equation can be seen in the following:

2H3 PO4 + Fe2O3 = 2FePO4 + 3H2O

The hard-to-clean iron oxide turns into blackish ferric phosphate (or iron phosphate) that can be scrubbed right off though it leaves iron phosphate as a coating on the metal surface due to chemical reaction effects. The water will be washed off during cleaning process. The effects of the acid on the metal surface will not be of significance unless exposed for a long period of time or at high concentrations.

The Egg That Went Bad

Can’t tell if your eggs are bad? You might want to call chemistry for a little help. Use the following steps:

Get a glass/ cup of tap water.
Place the egg inside.
Floats = Bad , Sink = Good

Now you might wonder, why so? The egg shell consists of about 7000 tiny pores. Logically speaking, over time, more gas will enter the egg. This causes the air cells to become larger thus the buoyancy of the egg.

more gas = more floating

Make sense? This, however, is partially correct. The real reason to why it floats is not not really due to air entering, rather the mass leaving the egg. The density solely depends on the mass because the egg shell does not contract or expand. If it weighs more, it sinks. Weighs less and it will float. Hence, we can say that density of a good egg is higher than that of tap water, which enables it to sink.

Density = Mass / Volume

As the egg decomposes, water vapour and other gases leaves the egg through the porous shell and surrounding air will enter though the overall mass is reduced as the yolk and whites shrink, making the air cell larger.

more mass leaving = lesser density = floating

Glowstick

Light sticks come in a variety of colors. The color of the light is determined by the chemical make-up of the fluorescent dye in the stick. Light sticks use energy from a chemical reaction to emit light. This chemical reaction is set off by mixing multiple chemical compounds.

When you combine 2 or more compounds, the various atoms may rearrange themselves to form compounds. Depending on the nature of the compounds, this reaction will cause either a release or an absorption of energy. The reaction between the different compounds in a light stick causes a substantial release of energy. The atoms in the materials are excited, causing electrons to rise to a higher energy level and then return to their normal levels. When the electrons return to their normal levels, they release energy as light. This process is called chemiluminesence.

A typical light stick holds a hydrogen peroxide solution and a solution containing a phenyl oxalate ester and a fluorescent dye. Here’s the sequence of events when the two solutions are combined:

When you bend the plastic stick, the glass vial snaps open, and the two solutions flow together. The chemicals immediately react to one another, and the atoms begin emitting light.
The hydrogen peroxide oxidizes the phenyl oxalate ester, resulting in a chemical called phenol and an unstable peroxyacid ester.
The unstable peroxyacid ester decomposes, resulting in additional phenol and a cyclic peroxy compound.
The cyclic peroxy compound decomposes to carbon dioxide.
This decomposition releases energy to the dye.

The electrons in the dye atoms jump to a higher level, then fall back down, releasing energy in the form of light.

Before you activate the light stick, the two solutions are kept in separate chambers. The phenyl oxalate ester and dye solution fills most of the plastic stick itself. The hydrogen peroxide solution, called the activator, is contained in a small, fragile glass vial in the middle of the stick. When you bend the plastic stick, the glass vial snaps open, and the two solutions flow together. The chemicals immediately react to one another, and the atoms begin emitting light. The particular dye used in the chemical solution gives the light a distinctive color.
Vinegar + Baking soda
Complete this part. I can’t continue with the slides if this is incomplete. Coco, do your part.

Conclusion
Help with this part as well.

Credits part as well. Do it at the bottom. Here are my sources:

Rust on pan:
http://ecologicarchitecture.com/SoloHobbit/rust/
http://www.snopes.com/cokelore/acid.asp

Onions:

http://www.customs.go.jp/ccl/e_kids/4.htm
Rotten egg:
https://www.scientificamerican.com/article/salty-science-floating-eggs-in-water/
http://awesci.com/why-do-bad-eggs-float/

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