Thank You

The "Coke + Mentos = ?" post sums up our University Chemistry 1 assignment blog, together with "Ice Cool When Needed", "Antioxidants - Producing Quality Food", "Detergent: Get Off My Way, Mr. Stain and Ms. Dirt", and finally "The Culprit of Love".

Four of us from the Group 17 (not the Periodic Group) would like to thank Ms. Alice Phua for giving us an opportunity to explore chemistry used in our daily life and also her lecture for this semester.

Hope you have fun reading this blog ! Thank You !

Coke + Mentos -> ?

Ever wonder why parents do not allow kids to eat sweets and drink soda at the same time?

It can go KABOOOMMM, if the combination of chemicals are right.

The Mythbusters team explained that, non-mint mentos ans diet coke, turns the liquid carbon dioxide into gaseous carbon dixoide.

CO_{2 (aq)} --> CO_{2 (g)}

This is due to the wax of the non-mint mentos that have crates on their surface that enable the wax to react with the carbon dioxide of soda. Diet coke has a higher content of carbon dioxide liquid due to the reduction of sugar, therefore, the reaction will be more intense as every surface of the mentos that have contact with the diet coke creates carbon dioxide gas, CO₂. As the mentos sinks into the bottle of the coke, pressure will build from the bottom of the bottle, enabling carbon dioxide gas to push some of the diet coke out. This theory applies to all sodas and candy, just that the combination of non-mint mentos and diet coke has the highest rate of reaction.

So, for all the sweet tooth out there, remember to avoid taking candy and soda at the same time !

Ice Cool When Needed

When we are fever, we normally apply a cold pack on our forehead. It helps to reduce heat as heat is transferred from the higher temperature to the lower temperature to achieve equilibrium. 

However, what is inside a cold pack? Just normal water or ice?

In fact, ice pack contains chemical that can react with water endothermically. As we learn in this University Chemistry 1 course, endothermic reaction absorbs heat from the surrounding. This is what causes an ice pack to be ice cold when in use.

In cold pack, there is a strong bag containing the ammonium nitrate salt and a thin bag containing water. When the cold pack is squeezed, the bag containing water breaks, causing the water to react with ammonium nitrate. This reaction is very endothermic, where the temperature can drop as much as 18 °C.

NH₄NO_{3 (s)} + water --> NH₄NO_{3 (aq)}

ΔH = + 26 kJ mol^-1

Besides reducing fever, cold packs also used by physiologist in sports to reduce swelling and pain due to muscle or joints sprain suffered by a player. This is to cause vasoconstriction in the blood vessels of the injured section, and also deadens the pain receptors.

So, when we use cold packs next time, we know its contents !

Antioxidants - Producing Quality Food

What are antioxidants?

The prefix "anti" means against and "oxidant" is commonly known as free radicals which might harm our body. Basically, they are substances that reduce, neutralize and prevent damage done to the body by free radicals. They prevent oxidation from occurring.

Why free radicals are harmful to our body?

It is because these external sources undergo oxidation due to the exposure to sunlight and pollution. This causes the breakdown of cell which produce free radicals to attack and destroy healthy cells.
Vitamin C (ascorbic acid) and Vitamin E (α-tocopherol) are the safest antioxidants.

• Vitamin C inhibits the formation of carcinogenic nitrosamines, stimulates the immune system, protects against chromosome breakage and reduces the risk of certain cancer. Oranges and limes are rich with Vitamin C.
  

• Vitamin E is leading antioxidants which neutralizes free radical compounds before they can damage cell membranes and helps to reduce the risk of heart diseases and cancer. It also boosts the immune system's ability to fight off diseases by increasing the level of interferon and infection. Vitamin E can be found in kiwi, milk, eggs etc.
  

All food are vulnerable to oxidation, especially when they contain fats and oils, which can turn rancid, that is, the fats and oils are oxidized to volatile organic compounds with foul odours (for example, butanoic acid). Antioxidants are added to fats, oils, cakes, sausages, biscuits, and fried foods to slow down the oxidation process. Antioxidants are also used in cosmetics to slow down the aging process of skin.

Therefore, antioxidants are useful for our daily life and also important to our body.

Detergent: "Get Off My Way, Mr. Stain and Ms. Dirt !"

How do you clean your floor and kitchen?

How do you wash your dirty clothes?

No doubt, detergent is used.

What is detergent?

Detergent is a substance used to enhance the cleansing action of water. It acts similarly to soap but it is made from chemical compounds rather than fat and lye. Detergent is a surfactant (substance that reduces surface tension) which used to dislodge dirt from soiled surface and retain it in suspension, allowing it to be rinsed away. Water cannot clean clothes alone because it won't attach to molecules of dirt or grease. But, detergent molecules have a hydrocarbon portion (hydrophobic tail), soluble in oil; and an ionic portion (hydrophilic head), soluble in water.

It also acts as an emulsifier, by bridging the water and oil phases, it breaks the oil into tiny droplets suspended in water. The disruption of the oil film allows the dirt particles to become more soluble. Detergents can be in any form such as liquid, powder, paste, bar, cake, shaped and etc.

It can be used for household, institutional or industrial purposes as it is effective in both soft and hard water. Functions of detergents are washing or cleaning laundry, fabrics, dishes or kitchen utensils, as well as hard surfaces.

So, how does detergent work?

Firstly, during the wash cycle of the washing machine, the surfactant mixes with water.

Secondly, the grease-loving ends (hydrophobic tails) of the surfactant molecules start to attach themselves to the dirt on the clothes. Subsequently, the dirt and grease are broken into smaller and easier-to-remove pieces by the tumbling motion.

After that, water molecules move past and attach themselves to the water-loving end (hydrophilic heads) of the surfactant molecules during the rinse cycle.

At last, the water molecules pull the surfactant and dirt away from the fabrics. The dirty water flushes away during the final spin.

Finally, we get our clean clothes again!

The Culprit of Love

Even wonder what causes the feeling of love, in terms of Chemistry?

Its Phenylethylamine (PEA).

It has a formula of C₈H₁₁N

 

IUPAC Name: Phenylethan-2-amine

Phenylalanine is a α-amino acid, which is the precursor to the release of phenylethylamine (PEA). When you stare into one's eyes, or get in contact with one's skin, it may trigger the release of PEA, if the one is your love. This is the forces of attraction between a boy and a girl.

PEA is a neurotransmitter in the limbic system of the brain, which travels along the neurons, into the bloodstream and causes the heart to beat faster, blood pressure rises, the face and skin flushes, the eyes flutter, and the pupils dilate. This natural amino acid causes the on-top-of-the-world, or "high" feeling in us.

 When the level of PEA is high, lovers would feel that "love is blind", perceiving his/her loved ones' good sides and discarding the bad sides. On the other hand, when the level of PEA is low, one may feel depressed.

Chocolate and strawberries contain PEA. Small amount of chocolate can make us happy, but large amount of chocolate will only lead to headache. This is because the PEA is quickly broken down by our body system so that it cannot reach our bloodstream.

When the relationship between a boy and a girl is stable, the level of PEA will then reduce back to normal, allowing endorphins to take over.