Hi guys.

Can you guess the title of my next video?

Oh.

Dance party.

Hurry up.

Write your guess in the comments section below.

Something's missing.

Sugar?

Salt?

No.

It's saliva.

To taste food,

The taste buds on our tongue need a liquid medium like saliva to bind food molecules to its receptors.

Saliva also contains an enzyme called amylase which breaks carbohydrates into simple sugars.

So, without saliva, foods having carbohydrates may taste different.

Also, saliva contains natural disinfectants which help wipe away harmful pathogens.

Topic: Sound.

Why do we hear echoes?

Hey.

Hold On.

Don't go into that room.

You don't want to listen to me.

Okay.

Then go ahead.

See, I warned you.

Will you listen to me now?

Don't worry.

The sound you heard was just an echo of your voice.

Let me explain what an echo is.

When we speak or laugh in a big empty hall, we hear our own sound repeatedly.

This is because our sound waves get reflected from the walls of the hall back to us.

The reflected sound that we hear is called an echo.

Hence, an echo is defined as the repetition of sound caused by the reflection of sound waves.

From a hard surface back to the listener.

Hey.

What are you doing?

Are you trying to hear an echo?

It is not that easy.

There are 2 ideal conditions for an echo to be heard.

When we speak or laugh, we hear our original sound at that moment.

The sensation of this original sound remains in our brain till 0.1 seconds.

This time is called the persistence of hearing.

When we utter sounds, some of our sound waves get reflected while some get absorbed.

If the reflected sound waves reach our ears before the completion of 0.1 seconds.

Then our brain does not perceive the original and reflected sounds as separate sounds.

They are interpreted as one sound.

Therefore, in order to hear two distinct sounds or an echo.

The time gap between the original sound.

The reflected sound or echo should be at least 0.1 seconds.

This is the first condition for an echo to be heard.

Do you know when the time gap will be more than 0.1 seconds?

This gets us to the second condition for an echo.

The minimum distance between the speaker and the reflecting surface should be at least 17.2 meters.

When the distance is 17.2 meters and we start speaking.

Assume that the original sound reaches our ears at this time.

The reflected sound reaches our ears at this time. , then the time interval between the reflected sound.

The original sound will be equal to 0.1 seconds.

As a result, we will be able to hear an echo.

Alright.

Now, let us try and hear an echo in this room?

It is even bigger than the previous room.

Now, why can't we hear an echo?

This is because there are many soft furnishings like sofas, carpets, curtains, etc., in this room.

They absorb most of the sound waves.

As the sound waves do not get reflected, we are not able to hear an echo in this room.

Hence, one more thing to consider.

If we want to hear an echo, is that there should be minimal use of such sound absorbing materials.

Topic: Distillation.

Is distilled water safe to drink?

How would I know?

Am I a detective?

Alright, alright.

I'll answer it.

Distilled water is obtained from distillation.

In distillation, the impure water is first heated, thus converting water to vapor.

Then, this vapor is condensed by cooling, hence converting vapor back to liquid water.

By this process, the impurities remain behind, giving us pure distilled water.

Now, even though distilled water is pure.

Some doctors say that we should not drink it for a prolonged period of time.

So, can I take a bath with it?

I haven't bathed since last Sunday.

Oh gross.

You are just impossible.

It is generally recommended to avoid drinking distilled water for a long period.

Because along with the impurities.

The minerals required for the proper growth of our body are left behind during distillation.

What is asthma?

It is a nickname for cinema.

Stop bluffing.

Asthma is a lung disease.

A person with asthma has red and swollen bronchial tubes with a lot of mucus.

As a result, the bronchial tubes get narrower than normal, thus making it hard to breathe.

Besides this, the bronchial tubes are highly sensitive to irritants like pollen, tobacco smoke, dust, etc.

When an asthmatic person inhales an irritant.

The tubes become much more swollen and more mucus is produced.

This causes further narrowing of the tubes.

This narrowing makes exhalation harder than inhalation.

Hence, carbon dioxide rich air gets trapped in the person's body.

He does not get sufficient supply of fresh oxygen.

As a result, the person can have severe shortness of breath and a feeling of tightness in the chest.

When an asthmatic person experiences such problems, he is said to have an asthma attack.

What are those 'do not eat' packets?

It is a top secret.

No.

It's not.

Do not eat packets usually contain silica gel which is a form of silicon dioxide.

Silica gel packets or do not eat packets are commonly found in products like packaged foods.

Leather articles, etc. because these products get spoiled by moisture.

Silica gel helps to keep them safe by adsorbing the moisture.

You mean absorbing the moisture, right?

No.

Absorption is a process in which a substance is taken into another substance.

Whereas,

Adsorption is a process in which a substance attracts and holds another substance on its surface.

Now, silica gel contains millions of microscopic pores.

If there is any moisture present around the leather articles or packaged foods.

Then the pores of silica gel attract the moisture and hold it on their surface.

Preventing the products from getting spoilt.