B2 High-Intermediate US 23 Folder Collection
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Why do leaves change color and fall?
Leaves contain various colored pigments like orange, yellow, green, etc.
But among all these pigments.
Only green colored pigment called chlorophyll traps sunlight and helps leaves prepare food.
Now, since green colored chlorophyll has such an important function.
The amount of chlorophyll is much higher in leaves, causing them to usually appear green.
No, they're black.
I'm wearing sunglasses.
Now during autumn or fall, there is not enough sunlight for chlorophyll to trap.
As a result, leaves are not able to prepare
much food.

Hence, the plant begins to shed its leaves
instead of wasting energy on their maintenance.

However, before shedding, the plant absorbs required nutrients from the leaves and breaks down chlorophyll.
Now, since chlorophyll is broken down, other pigments in leaves become visible, resulting in the change of color.
Can you guess the title of my next video?
Hurry up.
Write your guess in the comments section below.
Why is fluoride added to water?
To make water taste like soft drink.
According to a prevailing study.
When fluoride is added to public water supplies at an average concentration of about 1 part per million or slightly below.
It prevents tooth decay.
But how?
Enamel is the hard outer covering of our tooth.
It is primarily made up of hydroxyapatite.
Hydroxylapatite is a compound of calcium,
phosphorus and hydroxide.

Now, when bacteria in our mouth feed on food
particles, they produce acid.

This acid dissolves the hydroxyapatite, leaving behind a residue of calcium and phosphate ions.
This results in a tooth decay.
Now, when we drink water containing fluoride.
The fluoride binds with calcium and phosphate ions,forming fluorapatite.
As fluorapatite is less susceptible to acid
attacks, it helps to stop the tooth decay process.

Why do we need sleep?
Because we like to be lazy.
There are basically two factors that make
us sleep.

One of them is light.
When we see light in the morning, our brain
releases more amount of cortisol which keeps us awake.

While when it is dark, our brain releases
more amount of melatonin which makes us sleep.

Besides this.
Our brain performs various activities throughout the day which results in the production of adenosine.
Accumulation of this adenosine is the second factor that makes us sleep.
Now, when we sleep our brain gets time to
reabsorb the accumulated adenosine.

So that our brain is ready for the next day.
Besides this, sleeping helps our brain to reorganize information and clear out unwanted memories.
Moreover, while sleeping, we use very less

Thus, sleeping also helps us to conserve energy.
Topic: Diffusion.
Why can we smell hot food from a distance?
Looks like you have lost your way.
I know the way.
Don't listen.
See, I told you.
Now, listen to me.
There is a restaurant next to your house where hot sizzling food is available, right?
Ohh yeahh.
Follow its smell and you will reach home.
I have reached home.
Do you know how the smell of that food reached you?
When food gets cooked, it releases some aromatic gases into the air.
The molecules of these gases spread and mix with air molecules.
When this air reaches our nose, we get the
smell of food.

This process of spreading and mixing of a
substance with another substance is called diffusion.

But then, why couldn't I smell the food inside my house from a distance?
This is because that food had become cold.
On heating food, the molecules of its aromatic gases gain kinetic energy and start vibrating faster.
They spread and mix easily into air, leading
to an increased rate of diffusion.

As the food gets cold, the temperature of
the aromatic gases decreases.

The kinetic energy of molecules decreases and they do not vibrate as much anymore.
Thus, the rate of diffusion decreases and
we cannot smell the food from a distance.

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Why do leaves turn yellow? | #aumsum

23 Folder Collection
AumSum published on April 15, 2019
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