Water is lighter as a solid than as a liquid.
Moreover, most substances expand and become lighter when their temperature increases while in a liquid state, but water, oddly enough, is heaviest at 4℃.
If ice were heavier than water at 0°C, ice cooled on the surface would sink to the bottom as soon as it was formed.
Whether it's a river or an ocean, the bottom will be covered in ice.
But as everyone knows, ice stays on the surface of the water.
This is why aquatic life can survive even when the temperature drops below 0℃.
Why is solid water lighter than liquid water? The reason lies in the way water molecules are bonded together.
A water molecule is made up of two hydrogen atoms bonded to one oxygen atom.
Here, the two hydrogen atoms form a broken line at a certain angle (104.5℃).

The hydrogen atoms of a water molecule and the oxygen atoms of other surrounding water molecules attract each other due to their positive (+) and negative (-) charges.
This bond is called a hydrogen bond.
Hydrogen bonds are stronger than the attraction between ordinary molecules.
To put it differently, we can say that 'water molecules are molecules with a large electrical bias within the molecule.'
---From "The Scientific Reason Why Ice Doesn't Sink"

When asked, “What color is calcium?” many people will answer, “It’s white.”
The calcium we commonly encounter in our daily lives is a compound of calcium, and the simple elemental calcium (also called metallic calcium) that exists only in calcium is difficult to find unless you are a chemist.

The elemental substance of calcium belongs to the alkaline earth metals and has a silver color.
On the other hand, calcium compounds such as calcium carbonate (a component of limestone, eggshells, and seashells), calcium hydroxide (slaked lime), and calcium oxide (quicklime) are all white.
The simple elements sodium and potassium are also silvery metals, like calcium.
Note that each element will show a different color when burned in a flame.
---From "What color is calcium?"

The color of a firecracker depends on the chemical reaction of the flame.
When metallic element compounds are mixed into the fireworks, the color of the fireworks is determined by the type of metal.
Red is made from strontium compounds, green is made from barium compounds, yellow is made from sodium compounds, and blue is mainly made from copper compounds.
Colors other than red, green, yellow, and blue are created by mixing various compounds.

The shiny white color appears when metal powders such as aluminum or magnesium burn.
Inside the jade, there is a mixture of metal powder and an oxidizer (a substance that causes the metal to strongly bond with oxygen). When these two substances react with each other, a large amount of heat is generated, and the temperature reaches a high temperature of about 3,000℃, causing it to glow white.

When a flame reaction occurs, the electron energy in the metal changes from a low state to a high state due to the heat of the flame.
Since the high energy state is an unstable state for electrons, the electrons return to a lower energy state.
This is because light of visible wavelengths is emitted, allowing us to see color with our eyes.
---From "Why do fireworks have different shapes and colors when they explode?"

Freon was considered a dream substance because of its versatility.
But it soon became clear that freon was the main culprit in destroying the ozone layer.
So they started using alternative freon gas instead of freon.
Then, this time, we find out that substitute freon has a strong greenhouse effect.
In other words, it is a substance that causes global warming.

Nowadays, instead of freon-like substances, a substance called isobutane (C4H10), which is a combination of carbon (C) and hydrogen (H), is used.
Isobutane burns when ignited.
So, compared to Freon, there are some inconveniences.
Air conditioners and refrigerators still use alternative freon.
In the future, refrigerants will change, but for now, we are using alternative freon.
---From "Chemical Substances That Have Become Poisonous"

When crude oil is extracted, the first step is fractional distillation.
Fractional distillation is a method of separating components by utilizing the difference in boiling temperature (boiling point) in a solution containing two or more substances.
Using this fractional distillation, gasoline, liquefied petroleum gas (LPG), naphtha, kerosene, diesel, etc. can be obtained.

Liquefied petroleum gas is composed of low boiling point substances such as propane (boiling point approximately -42°C) and butane (boiling point approximately -1°C), so it ignites easily.
Gasoline, which is the fuel for automobiles, is composed of approximately 5 to 10 carbon atoms and has a boiling point of approximately 30 to 100°C.
Naphtha, a main raw material for the petrochemical industry, is a hydrocarbon mixture produced at a boiling point of 100 to 180°C during the distillation of crude oil.
From naphtha, raw materials such as ethylene, propene, and benzene can be obtained.

In addition, kerosene, which is used as a household fuel or jet fuel, has a boiling point of about 250 to 320°C and is mainly composed of hydrocarbons with about 11 to 15 carbon atoms, while diesel fuel, which is used as a fuel for diesel engines, has a boiling point of about 250 to 320°C and is mainly composed of hydrocarbons with about 15 to 20 carbon atoms.

---From "The Reason for Boiling and Separating Oil"