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00:00hi kids today we will learn what are reversible and irreversible changes so
00:10let's get started melting of ice is a change that turned ice into water
00:20burning of paper is a change that turned paper into ash folding of paper
00:29is a change that changed the shape of a paper growing a plant from a seed is a
00:38change that turned seed into a plant breaking of glass is a change that
00:49changed the form of a glass mixing of salt in water is a change that changed
00:58water into a mixture of salt and water so all these are changes changes can be
01:10classified into two types reversible changes irreversible changes now let's
01:21learn about them in detail reversible changes or physical changes are the
01:32changes that change the form or physical appearance of matter and do not change
01:38the amount of matter in an object and most of the physical changes are
01:45reversible changes now let's see some examples of physical changes filling a
01:53balloon with air here we have a balloon let's fill it with air now its shape is
02:04changed so there is a change in the shape of a balloon but this change can
02:13be reversed as we can let the air out of the balloon and the balloon will come
02:22back to its original shape so it's a reversible change or a physical change
02:30let's take another example of a physical or irreversible change it is melting of
02:41ice here we have a cube of ice let it stay for some time and it will melt so
02:53it's changed from solid state to liquid state but this change can be reversed
03:04that is you can freeze the same water and it will again turn into ice so
03:13melting is a physical or a reversible change now let's have another example
03:24sharpening a pencil if a pencil is sharpened only its shape is changed or
03:34physical appearance of the object is changed also the amount of matter is not
03:42changed only some amount of matter is separated from the pencil apart so it's
03:52a physical change but yes it's not a reversible change remember most physical
04:01changes are reversible not all physical changes are reversible here is another
04:10example cutting of an apple if an apple is cut into slices only the shape of an
04:22apple is changed also amount of matter is not changed only the object is
04:30divided into some parts also this change is not reversible here is another
04:38example of a change making a pot out of clay when clay is molded into a pot
04:47shape of clay is changed no new matter is formed and a fresh pot can be again
04:56made into a ball of clay so it is a physical change or a reversible change
05:06so we learnt physical changes are where shape or form of object is changed
05:15amount of matter is not changed but can be divided into more parts or some
05:23amount of matter is separated no new type of matter is created during this
05:30type of change all the phase changes are physical changes like melting freezing
05:42condensation all these are physical changes now let's learn about chemical
05:52changes or irreversible changes chemical changes are those changes that change
06:01the amount of matter in an object and some new type of matter is formed that
06:08entirely different from the original matter and are irreversible that is
06:14cannot be reversed once done let's see some examples burning a paper if a piece
06:27of paper is burnt it changes to ash that is some new type of matter is formed
06:35that is ash which looks exactly different from the original matter that
06:44is the paper this change cannot be reversed that is ash cannot be changed
06:52back into paper so it's a chemical change or an irreversible change here is
07:01another example rusting of iron here we have a metal which is not rusted and
07:09here we have a metal which is rusted this brown rough layer you see on the
07:17metal is rust and when a metal undergoes rusting a new type of matter is formed
07:27which is totally different from the original matter and rusting cannot be
07:34reversed so rusting is a chemical change and also irreversible change here is
07:44another example candle when you light a candle the size of the candle reduces
07:52with time so amount of matter is getting reduced and you cannot convert
08:01back the candle to its original size so it's a chemical change and also an
08:11irreversible change here is another example cooking eggs when we cook eggs
08:21new look of eggs appears and this change cannot be reversed that is you
08:31cannot convert cooked eggs back to their uncooked form so it's a chemical change
08:38or an irreversible change
08:44so kids today we learned two types of changes physical changes and chemical
08:53changes and we also learned that physical changes are mostly reversible
09:01and chemical changes are irreversible now you may go ahead and take a quiz to
09:09learn more bye-bye