Topic: Speed of sound.
Why does sound travel faster in summer than in winter?
Wow.
That was an amazing trick.
The television switched on immediately after you clapped.
I know.
This is one of my favorite tricks.
Now, I bet you that the television will not switch on instantly after your clap.
This time I am going to prove you wrong.
See.
I told you.
I lost again.
Do you know why the sound took more time to reach the television?
This is because the speed of sound decreased.
Speed of sound depends on the temperature of the medium.
Higher the temperature of the medium, more will be the speed of sound and vice versa.
So, in this case, what do you think is the medium?
Are you kidding me?
I don't know.
No Problem.
I will tell you.
In this case, air is the medium.
During summer season, the temperature of air increases.
At higher temperature, the molecules of air have more kinetic energy.
Hence, they vibrate faster leading to increase in speed of sound.
Now, during winter season, the temperature of air decreases.
With decrease in temperature, the kinetic energy of the molecules also decreases.
Hence, the molecules do not vibrate much.
As a result, the speed of sound decreases during winter season.
Topic: Ignition Temperature.
Why does a match light when you strike it?
Why don't you use a match instead?
You will be able to light the bonfire easily.
No.
I don't believe you.
Try it.
Look.
I told you.
Dude.
That was awesome.
This happened because of low ignition temperature.
Ignition temperature is the lowest temperature at which a combustible substance starts burning.
Lower the ignition temperature, more easily will it catch fire.
Now, a match head contains antimony trisulfide and potassium chlorate.
Enough.
I know how to use it now.
No.
The match will not light on any surface.
The rubbing surface of a matchbox has powdered glass and red phosphorus.
On striking the match against it, friction is caused.
Friction generates heat, converting red phosphorus to white phosphorus.
White phosphorus has a very low ignition temperature.
It immediately ignites in air, producing heat and light, thus beginning the process of combustion.
The heat produced breaks down the potassium chlorate present in the match head, releasing more oxygen.
This oxygen combines with antimony trisulfide which is also in the match head and keeps the flame burning.
Topic: Latent heat of vaporization.
Why do wet clothes feel cold?
Because..
I don't know.
It is because of latent heat of vaporization.
Latent heat of vaporization is the amount of heat energy required.
To change a unit mass of liquid into vapor.
Now, the value of latent heat of vaporization of water is very high.
Is it higher than Mount Everest?
No.
The latent heat of vaporization of water is about 22 point 6 times 10 to the fifth joules per kilogram.
This means it is smaller.
Please listen.
This means only 1 kilogram of water requires 22 point 6 times 10 to the fifth joules of heat energy.
To change to vapor.
Now, when we wear wet clothes, the water present in them absorbs quite a lot of latent heat from our body.
Evaporates into the atmosphere, making us feel cold.
Topic: Respiration.
Why should we not overwater potted plants?
It's because the water will overflow and make the floor dirty.
No.
Leaves of a plant take in oxygen from the air present in the atmosphere.
While, the roots, being buried in the soil.
Take in oxygen from the air present in tiny spaces of the soil.
When we overwater a potted plant, the air in the tiny spaces gets replaced by water.
So, do the roots know how to swim in water?
Please listen.
As air gets replaced by water.
The roots do not get sufficient oxygen to breathe and they begin to rot.
This may adversely affect the growth of the plant.
Thus, we should always try to supply adequate water to the potted plants and not overwater them.
Topic: Transpiration.
Why do cacti have spines?
Maybe they want to look like porcupines.
Very funny.
Spines help cacti to reduce transpiration.
Well.
I know all about vibration, but what's this new thing called transpiration?
Transpiration is the loss of water from ariel parts, like stems and leaves, in the form of water vapor.
These ariel parts contain stomata which allow water vapor to escape into the atmosphere.
So, shall we tape the ariel parts so that the vapor won't escape?
Pay attention.
In deserts, where cactus usually grows, there is scarcity of water.
Also, due to high temperatures, the rate of transpiration is very high.
Thus, the leaves of a cactus have modified into spines.
Spines don't have stomata.
Thus, the rate of transpiration is reduced, helping the cactus to save water.
Topic: Nerves.
Why don't we feel pain when we cut our hair?
Because if it would, then we would have got angry on our hair dressers.
You are just impossible.
Wait.
I will explain it to you.
Inside our body, there is a network of nerves.
These nerves help us to sense our surroundings and feel pain, touch, etc. by sending messages to the brain.
So, do the nerves of my hair not know how to send a message?
No.
Generally, the part of our hair above the skin is made up of dead cells.
It does not have any nerves.
Hence, when we cut our hair, due to the absence of nerves, our brain does not receive any messages of pain.
As a result, we don't feel any pain.
Topic: Wavelength.
Why red is used as a danger signal?
Well.
Because my teacher said so.
As usual, you are wrong.
The major reason for red to be used as a danger signal is its wavelength.
I know.
Wavelength is the distance between two sea waves.
No.
In the wave theory of light.
The distance between successive crests or troughs is called wavelength.
Longer the wavelength, lesser will be the scattering of light.
Now, among the colors of visible light, red has the longest wavelength.
Hence, it is least scattered by the atmospheric particles.
As a result, whether it is fog or smoke, red light passes comparatively easily through them.
Thus, it can be seen from maximum distance, making red color the right choice to convey any danger.
Topic: Bad Conductors of Heat.
Why are two thin blankets warmer than one thick blanket?
Because two chocolates are better than one.
No.
To understand this, we need to first learn about bad conductors of heat.
Bad conductors of heat are the materials which do not allow heat to easily flow through them.
Air, wood and glass are some examples of bad conductors of heat.
In these examples, is our train conductor included as well?
Just listen.
A thick blanket allows much of our body heat to escape into the atmosphere.
However, when we use two blankets one on top of the other, air gets trapped between them.
This air being a ad conductor of heat.
Does not allow our body heat to easily flow into the atmosphere, thus keeping us warm.
Topic: Breathing.
Why do we get hiccups?
We get them when our friends think of us.
No.
We get hiccups mainly because of our diaphragm.
Diaphragm is a dome shaped muscle between our lungs and stomach.
It generally works perfectly.
Just like me, right?
No.
When we inhale, our diaphragm contracts helping us take in air into the lungs.
When we exhale, it relaxes, helping us give out air.
However, sometimes this contraction does not happen properly.
One of the reasons is excess eating.
Eating too much too quickly causes our stomach to swell, causing discomfort to our diaphragm.
Due to this, our diaphragm contracts irregularly in a jerky way, making us suck air suddenly.
This air rushes through our voice box, making the vocal cords to close suddenly, creating a hiccup.
Topic: Latent Heat of Vaporization.
Why does steam cause more severe burns than boiling water?
It is because steam is jealous of boiling water.
No.
It is because of latent heat of vaporization.
Latent heat of vaporization is the amount of heat energy required.
To change a unit mass of liquid into vapor at atmospheric pressure at its boiling point.
Trust me.
Everything just went over my head.
Alright.
I will explain it to you.
Boiling water contains only a specific amount of heat energy required for it to boil.
However, as steam is formed from boiling water.
It contains the heat energy of boiling water, along with the latent heat of vaporization.
Hence, as steam has more heat energy, it can cause more severe burns than boiling water.