changes-around-us.ppt

changes 6

1. Changes Around Us

2. What is change?
Everydayweobserve
changesaroundus.For
examplethechangeof
dayandnight,flowering
ofplants,ripeningof
fruits,rainfalletc.
Change is the transition of any substance from
one form to another.

3. Types of changes
Slow and fast changes
Desirable and undesirable changes
Reversible and irreversible changes
Periodic and non periodic changes
Physical and chemical changes

4. Slow Changes
Slow changes are those which take a long time
to occur. For example the germination of seed
to form plant, growth of child into an adult and
further into an old man, rusting of iron etc.

5. Fast Changes
Fastchangestake
lesstimetooccuror
Occurinstantaneously.
Forexampleburning
ofpaper,burstingof
balloon,burningof
matchstick.

6. Desirable Changes
Therearesomechangeswhichoccuraswe
wish.Welikesuchchangesthatiswhythese
arecalleddesirablechanges.Forexample
formationofcurdfrommilk,formationof
manurefromcowdunganddeadplants.

7. Undesirable changes
Therearesomechanges
whichdonotoccuras
perourwishes.Such
changesarecalled
undesirablechanges.For
exampleearthquakes,
excessiveheatindueto
riseintemperaturein
summersandbreaking
ofglass.

8. Sometimes undesirable changes
accompany desirable changes
Therunningofcaron
roadisdesirablebutit
alsoproducessmoke,
carbondioxideand
otherharmfulgases
whichpollutethe
environment.Henceit
becomes the
undesirablechange.

9. Some changes may be desirable
for one person but undesirable
for others.
Forexamplethecutting
oftreemaybemaybe
desirableforonewho
needs wood but
undesirableforothers
becauseitdisturbsthe
balanceinnatureas
treesproduceoxygen
whichisnecessaryfor
allhumanbeingson
earth.

10. Periodic Changes
Changes which occur
again and again after
fixed intervals of time
are known as periodic
changes. For example
change of day and
night, occurrence of full
moon, heart beat and
oscillation of pendulum
of clock.

11. Non-Periodic changes
Therearesomechanges
whichdonotrepeat
themselvesatregular
intervals.Youcannot
predictwhentheywill
reoccur.
Forexampleoccurrence
ofearthquake,train
accidents,sneezing,
rustingofironetc.

12. Reversible Changes
Ifachangecanbereversedthenitiscalled
reversiblechange.Forexampleoncooling
watertothefreezingpointitchangesintoice
andicechangesbackintowateronheating.

13. Irreversible Changes
Therearesomechangeswhichcannotbe
reversedsuchchangesarecalledirreversible.
Forexamplegrowthofchildintoanadultand
thenfromanadulttoanoldman.

14. Physical Changes
Changes in which
size or shape of the
object may change
but the substance of
which they are
made of remain the
same. For example
formation of water
vapours on heating
water.
Water
vapours

15. Chemical Changes
The changes in which new substances are
formed are called chemical changes. For
example rusting of iron lead to formation of
iron oxide.
2Fe + O2--------->2FeO
Iron Oxygen Rust
We can not get back iron or oxygen from iron
oxide. So it is a chemical change.

16. Conclusion
We should try to minimize changes
which adversely affect the human
beings or their environment.
For example: Cutting of trees, Pollution
etc.

17. Exercise
Tell which type of change is this:
Growing of a plant from a seed.
Evaporation of water.
Occurring of tides in the sea.
Revolving of earth around the sun.