LOGICS OF LIFE

 

 

 

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  • Fire walking

How do people walking on burning coal not burn their feet?

Answer:

Usually people wet their feet abundantly before walking on burning coal. When they start walking on the coal, this moisture (may also be due to sweat) evaporates and forms a protective gaseous layer beneath their feet.

In reality they are walking on a protective layer of water vapour (which has low heat capacity and poor thermal conduction) rather than on the burning coal, as one would believe. This is a short time effect and one should walk quickly to avoid any further damage.

Furthermore, the coal also plays a vital role in saving the feet from the heat. Coal or wood embers, on which people generally walk, have low heat capacity and poor thermal conduction. It means coal being a bad conductor of heat will not pass heat as efficiently as metals.

If we walk over steel pellets at the same temperature as that of the burning coal, the damage will be much higher as steel has much higher heat transfer i.e. conducting property.

Moreover the skin of human feet is a bit coarse. It is of a different texture from the rest of the body and has the capacity to withstand the temperature of burning coal for a few seconds.

 

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  • Lather's color

Soaps come in different colors. But why is soap's lather always white in color?

Answer:

Lather or foam is nothing but large collection of small soap bubbles. A soap bubble is, in turn, a very thin film of soap solution enclosing some air.

Because of the low surface tension of soap solution, the film can stretch and spread and form innumerable bubbles with a very large total surface area.

Due to this, whatever slight tint is present in the thin film of the colored soap solution gets subdued. Although a soap film is more or less transparent, the lather or foam looks white because the light striking this large collection of bubbles gets scattered.

That is the reason why all kinds of lather or foam appear white.

 

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  • Snake pits

How are snake pits formed?

Answer:

Snake pits are a network of caves and crevasses formed by underground water and collapsed limestone serving as perfect locations for hibernating snakes. In cold countries, these pits protect them from very cold temperatures, which tend to dip as low as minus 40 degrees Celsius during winter. The snakes huddle themselves below the frost lines during harsh winter.

Snakes of the tropical countries, however protect themselves from the heat of summer by staying in pits, which are formed far below the ground level. These are protected underground from surface heat.

Most snakes do not make their own burrows, but inhabit the burrows made by other creatures, such as rodents. They also inhabit termite mounds.

Only a few species of snakes, such as sand boas and shield tail snakes, are capable of making their own burrows, but even they prefer existing burrows, when available.

 

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  • Boiling milk

What causes milk to rise up when we boil it?

Answer:

Milk contains 87 percent water, 4 percent proteins and 5 percent lactose (milk sugar). When we boil milk, the fat, sugar, proteins and minerals get separated. Since they are lighter than milk they collect on the surface in the form of cream.

During heating some amount of water gets converted into vapour and the bubbles of water vapour rise to the top but the heat is conducted away by the layer of water and by the fat droplets that have a higher boiling point than water.

The vapour gets trapped in the creamy upper layer. As the milk is heated further the water vapour expands and thick foam is produced on the top.

As the milk is boiled continuously the water, which boils at 100 degrees Centigrade, produces more water vapour and pressure builds up in the boiling milk so that the vapour pressure raises the creamy layer. So the milk pushes the creamy layer out and milk spills out.

 

  • Hot core

Why is the Earth's core hot? What caused it to heat up? Is it still heating, or now cooling?

Answer:

Scientists estimate that temperature at the Earth's core is about 5538 deg. Celsius.

Much of the heat inside the Earth today comes from elements that were present when the planet was first formed billions of years ago. One theory is that radioactive decay of the primordial elements inside the Earth, U-238, Th-232, and U-235 and their radioactive products generate thermal energy (heat).

A nucleus - the central core of an atom - contains both protons and neutrons. Elements, such as the ones mentioned above, have a fixed number of protons but may exist with various numbers of neutrons.

The sum of the protons and neutrons makes up the mass number of an element. Isotopes of an element have the same chemical properties but different weights (indicated by the mass number). Radioactive elements are isotopes with an unstable nucleus.

The isotopes decay by emitting energetic alpha and beta particles until stability is reached. Alpha particles are the nuclei of ordinary helium atoms, which consists of two protons and two neutrons. Beta particles are electrons and positrons. The half-life of an isotope is the amount of time it takes for half of the atoms to decay into a more stable form.

Within the Earth, the released particles from the elements are slowed by friction through interaction with Earth material, thereby generating heat.

The primordial radioactive elements have half-lives on the order of a billion years. Hence, since the Earth formed, their abundance is decreasing over time as a function of their half-life. Therefore, Earth's core is not heating up, it's cooling down.