cornstarch

ever wonder why cornstarch thickens when u play it with your fingers?first of all, Cornstarch/water paste is an example of a non-Newtonian fluid, that is, a liquid whose viscosity changes, depending on how much force you use to get the liquid to flow. Viscosity is a measure of the liquid's resistance to flow (molasses has high viscosity; water's viscosity is much lower).
Pressing on the cornstarch suspension squeezes the water from between the particles. It resists flow because now the particles are grinding against each other. Releasing the pressure allows the water to seep between the particles again and the suspension flows more easily.
You can see the same effect with wet sand. The sand hardens under your feet. But if you lean over and draw a line in the sand with your finger, you'll see that it's rather soft

The Chemical Reaction While Cooking Rice

As rice contains about 90% starch, rice-cooking is essentially the reaction of starch in water at elevated temperatures. Starch granules adsorb water and swell as the heating continues. When a certain temperature (call gelatinization temperature) is reached, the cell wall of the granule breaks and the starch turns viscous (gelatinized). That is essentially what happens during the cooking of rice. There are two types of starch in rice, amylose and amylopectin. Long grain rice is rich in amylose, whereas short grain rice is rich in amylopectin. Cooked-rice properties vary, depending on the type of rice or the ratio of amylose and amylospectin in the starch. Thus, as we all know, when well cooked, long grain rice is much less sticky than the short grain rice.
Other than starch, which is carbohydrate, rice also contain some protein and fiber. As for nutrients in rice, they are mostly in the outer layer of rice called bran. Unfortunately, the bran is removed almost totally in the milling process. That's why we should eat brown rice (the rice with bran) not polished rice.

WHY DO ONIONS MAKE US CRY?

Who has never cried while cutting an onion? (well, apart from those who have never cut one hehehe). This is a little explanation in easy terms.Inside the onion cells there are some chemical compounds that contain sulfur. When you cut an onion its cells are broken and those chemical compounds then undergo a reaction that transforms them into a more volatile sulfured products, which are released into the air.These sulfured compounds react with the moisture in your eyes forming sulfuric acid, which produces a burning sensation. The nerve endings in your eyes are very sensitive and so they pick up on this irritation. The brain reacts by telling your tear ducts to produce more water, to dilute the irritating acid. So you cry to keep your eyes protected from the acid.There are some tricks to make onion-dicing less problematic:- Chop the onion under cold water. The volatile sulfured compounds will be released but then they react with the water, instead of reaching your eyes.- You can freeze the onion for 10 minutes before cutting it. The cold temperature of the onion will slow down the chemical reaction which forms the volatile sulfured compunds.

why does coffee keep us awake?

It is well-known that the effect of coffee on mood is related to its content in caffeine... But why caffeine has such a strong effect on us? Caffeine operates using the same mechanisms of amphetamines, cocaine, and heroin to stimulate the brain, though with milder effects. It manipulates the same channels as the other drugs, and that is one of the things that gives caffeine its addictive qualities.There is a chemical in our brain called adenosine, that binds to certain receptors and slows down nerve cell activity when we are sleeping. To a nerve cell, caffeine looks like adenosine and it binds to the adenosine receptors. However, as it's not really adenosine, it doesn't slow down the cell's activity like adenosine would. So the cell cannot "see" adenosine anymore because caffeine has taken up all the receptors adenosine binds to. Then, instead of slowing down because of the adenosine level, the cells speed up.The pituitary gland sees all of this activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline. Adrenaline is the "fight" hormone, and it makes your heart to beat faster, the breathing tubes to open up, the liver to release sugar into the bloodstream for extra energy and your muscles to tighten up, ready for action. Because of this, after consuming a big cup of coffee your muscles tense up, you feel excited and you can feel your heart beat increasing. Moreover, as amphetamines, caffeine also increases the levels of dopamine, which is associated with the pleasure system of the brain, providing feelings of enjoyment and reinforcement.

what makes people fall in love???;P

Falling in love - Attraction
When you fall in love you may have many physical symptoms: loss of appetite, can't sleep, can't concentrate, palms sweat, butterflies in stomach...i bet everyone has experienced this feeling before..hehe. This is due to surging brain chemicals called monoamines:- DOPAMINE: it's commonly associated with the pleasure system of the brain, providing feelings of enjoyment and reinforcement to motivate us to do certain activities. It's released by naturally-rewarding experiences, such as sex or food. Some research studies show that when female rodents were injected dopamine in the presence of a male rodent, the female will pick him out of a crowd later.- PHENYLETHYLAMINE: It's a natural amphetamine like the known drug and can cause the same stimulation effects. It contributes to that on-top-of-the-world feeling that attraction can bring, and gives you the energy to stay up day and night with a new love.- SEROTONIN: it controls impulses, unruly passions, obsessive behavior, aiding the sense of "being in control".- NOREPINEPHRINE is another neurotransmitter which induces euphoria in your brain, exciting the body by giving it a booster dose of natural adrenaline. This causes the heart to beat faster and blood pressure to rise. That's why you can experience a pounding heart or sweaty palms when you see someone you're attracted to.