My granny was a chemist!: One grain of rice

Everything around you is made of very, very small parts. They are so small your eyes can't see them. For example. When you eat your dinner today pick up one piece of rice and look at it. It has 100,000,000,000,000,000,000,000 atoms in it! A number that has 23 zeros is called 100 sextillion. We'll learn what an atom is later in this lesson.

The small, small parts that everything is made of have special names and qualities ( کیفیت های خاص ). For example. The qualities of water make it boil ( جوشیدن ) slower than oil.
The different ( مختلف ) parts ("particles") in things have names. Some parts are called molecules and atoms. Inside atoms there are parts called protons, neutrons and electrons. The smallest particles (little parts) in the universe ( کائنات ) are called quarks.

The things in your house are all different and have different uses. Why is that? They are different because of their unique ( منحصر بفرد ) atoms and molecules. For example. A metal pan gets hot when you put it over a fire but it doesn't melt ( ذوب شدن ) or burn up ( خاکستر شدن - سو ختن ). So you use a pan, not a pillow, to cook eggs. But why doesn't a pan burn up in the fire but a pillow would burn up?

And when you are cooking eggs, why does the clear part of the eggs turn white but the yolks stay yellow?!

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Now let's talk about how you use chemistry when you cook. What happens to atoms and molecules in food when we cook? To start, let's learn what happens to water and oil ( روغن پخت و پز ) when we cook with them. First look at these definitions (تعاریف).
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• atom: the basic unit or building block ( بلوک ساختمانی ) of all material (مواد) things. The center inside an atom is called the nucleus. And the nucleus is made of particles called protons and neutrons.

• molecule: one or more atoms that hold together and have the same qualities ( کیفیت ها ). A molecule is the smallest unit ( واحد ) that can have a chemical ( شیمیایی ) reaction ( عکس العمل ).
• polar: when one side of a molecule has a positive ( مثبت ) charge ( چارج) and the other side has a negative ( منفی ) charge ( چارج ).

A water molecule is polar. One side of it has a positive charge and the other side has a negative charge. The negative side of one water molecule is attracted to ( جذب شدن به ) the positive side of another water molecule. So they move together. That makes water dense ( متراکم ).
Oils and fats ( چربی ها ) are not polar. Oil molecules are attracted to weaker ( ضعیف تر ) parts in each other. The parts do not come that close to each other and so oil is not dense.

📍What can we learn from this? A lot!

1) Oil floats ( شناور ) on water. Water molecules are more dense and can hold up oil molecules.
2) Oil heats faster than water because water takes more energy (so more time) to break up its molecules. Weaker oil molecules break up faster and so heat faster.
3)  Water boils at a higher temperature than oil. So water takes more time to cool down.
4) You can only fry food in oil. You cannot fry food in water because water can't get hot enough to fry something. Water would evaporate ( برای تبخیر شدن ) before it was hot enough to fry something.  Water molecules boil at 100°C. Food starts to brown and crisp at about 140°C.  Only oil molecules can heat up to that temperature to fry your potatoes.

Oil gets hot at a lower temperature than water. As the oil turns the food brown it also forms a crust ( پوسته ) on the food. The crust keeps water inside the food from escaping ( برای فرار ). So the water inside the food gets hot and cooks the food from the inside too. That makes fried food "hard" on the outside and soft on the inside. People have fried food in oil for more than 2500 years!

But there is another way you can heat up and brown your potatoes without oil. Can you guess what it is? (Answer below.)

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Bake them in an oven! V
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HOME EXPERIMENT
You can do this at home yourself!

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The water weighs more!
The water (and container) weigh 8 ounces.
The oil (and container) weigh 7 ounces.