Crystallisation - Physical and Chemical Changes - CBSE Class 7 Science Video Lecture

Crystallisation.
Food tastes good due to the addition of salt in it.
Hey friend.
Hello.
I have prepared some delicious soup.
Do you know how salt is obtained?
No idea.
I will tell you how.
Salt is obtained by the evaporation of seawater.
However, this salt is impure and has small crystals.
This salt can be converted into pure state by the process of crystallization.
Crystallization is the process of formation of large crystals in pure state from their solutions.
Let us do an activity to understand crystallization.
Activity time.
Come with me.
You will assist me in this activity.
I am not interested.
If you assist me, then i will give you a reward.
Now, get me some water.
Take some water in a container and heat it.
The water has started boiling.
Now, get me some salt.
Got it.
Once water starts boiling, slowly start adding some plain salt to it.
Careful, this mixture is hot.
Stir mixture constantly and keep on adding plain salt to it until no more of the salt can dissolve in water.
Seems like enough salt has been added.
Now, we will filter the solution.
Filter the solution.
Interesting.
Now, we will allow the solution to cool.
After a while.
I think the solution has cooled by now.
Now, pass me the string.
Take a stick and tie the string to it.
Now, place the string inside the solution.
In the meantime, we will go on a vacation for a few days.
Wow.
See you after some days.
After few days.
After pulling the string out, we will see large salt crystals attached together on it.
This is the process of crystallization.
Very interesting.
Take your reward.
Thanks.
Safety Rules.
This experiment should only be done under adult supervision.
The boiling water can get extremely hot, so care should be taken while performing this experiment.
The End.