Ch-1: Chemical Reactions & Equations

Burning of a magnesium ribbon in air and collection of magnesium

oxide in a watch-glass

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Chalo
Clean it with sandAb Ise AASAN BHASHA MEI Samajhte hai :
paper.
Hold the magnesium ribbon with
Take about 2 cm a pair
longofmagnesium
tongs , and start heating. its other end.
ribbon
The Magnesium Ribbon starts burning.
Clean it with sand paper.
BUT IT'S NOT BURNING ALONE.
HoldIt the
startsmagnesium
burning with a ribbon with a pair
WHITE DAZZLING of .tongs , and start heating its
FLAME
other
And now to collect the Magnesium Oxide end.hold it over a Watch Glass
Powder
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

Q: Why Magnesium ribbon is cleaned before burning in the air ?

Ans: The magnesium ribbon which we use usually has a coating of ‘magnesium oxide’
on its surface which is formed by the slow action of oxygen of air on it. So, before
burning in air, the magnesium ribbon is cleaned by rubbing with a sand paper. This is
done to remove the protective layer of magnesium oxide from the surface of
magnesium ribbon so that it may readily combine with the oxygen of air (on heating).

Q: Why the magnesium ribbon should be burned by keeping it as far as

possible from the eyes?
Ans: The dazzling (very bright) white light given out during the burning of magnesium
ribbon is harmful to the eyes. So, the magnesium ribbon should be burned by keeping
it as far as possible from the eyes.

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 Formation of Precipitate

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

(i) Take some lead nitrate solution in a test-tube (or a
beaker).
(ii) Add potassium iodide solution to it.
(iii) A yellow precipitate of lead iodide is formed at once.
(iv) A change in colour (from colourless to yellow) also
takes place in this chemical reaction.

Chemical Reactions that evolve Gases AND RIse In Temperature

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

(Take some Zinc Granules in a Conical Flask
Now on Adding the Sulphuric Acid you will See a Magic.
As You will see the bubbles of HYDROGEN GAS forming around the zinc metal
We verified that it is Hydrogen gas because its bubbles burnt with pop sound
when passed through soap solution (As shown below diagram)
Also, if we will touch the flask with our hands we will see that it is too HOT.
So we get to know that along with evolution of gas temperature also rises in
the Chemical Reactions.

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 Decomposition reaction of ferrous sulphate.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 grams of Ferrous Sulphate Crystals in a DRY Boiling Tube.
They are originally Green In Colour
Heat the boiling tube over a burner
Now You will again see the magic.
As the green colour first changes to White And then Finally a Brown Solid is
formed(which is ferric oxide)
So the main observation of this activity is that the smell of burning Sulphur
comes out along with the colour change from Green to White and then Brown.

Decomposition reaction of lead nitrate

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 grams of lead nitrate powder in a boiling tube. Lead nitrate is a
colourless compound.
Hold the boiling tube in a test-tube holder and heat it over a burner.
Brown fumes of nitrogen dioxide gas are evolved which fill the boiling tube.
If a glowing splinter is held over the mouth of the boiling tube, it catches fire and
starts burning again. This shows that oxygen gas is also evolved during this
reaction.
A yellow solid is left behind in the boiling tube. This is lead monoxide (Please
note that lead monoxide is reddish-brown when hot but yellow when cold).

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 Decomposition of silver chloride is caused by light

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 grams of silver chloride in a china dish. It is white in colour.
Place this china dish in sunlight for some time .
We will find that white silver chloride turns greyish white (due to the formation of
silver metal).
Silver bromide also behaves in the same way as silver chloride with light energy.

Displacement reaction between iron (nail) and copper sulphate

solution.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 10 mL of copper Sulphate solution in a test tube.
Its original colour is Deep Blue
Now take a big iron nail and clean it same like u did with Magnesium Ribbon
using the sand paper.
Now put the iron nail in the solution and then see the magic.
After sometime like half an hour we will see that the iron nail would be covered
with red-brown layer.
And this layer would be of our another metal that is Copper.
So Finally we will see that the original Deep blue colour has faded and the
solution turns to light Green Colour.

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Double displacement reaction between barium chloride and
sodium sulphate.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take 3mL of Sodium Sulphate solution in a test tube .
And take 3mL of Barium Chloride but in another test tube .
Add Barium Chloride solution to Sodium Sulphate solution
And the magic we see is now of White colour as a White Precipitate is left over in
the Test Tube.

Oxidation of copper to copper oxide

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 1 gram of copper powder in a china dish. It is redbrown in colour.
Heat the china dish strongly over a burner (see Figure 55).
A black substance is formed. This black substance is copper oxide

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 Ch-2: Acids, Bases and Salts

Reaction of zinc granules with dilute sulphuric acid and testing

hydrogen gas by burning

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.
BHASHA MEI Samajhte hai :
Take a few piecesTheofMagnesium
zinc granulesRibbon starts
in a boiling tubeburning.
and add about 5 mL of
dilute sulphuric acidBUTto itIT'S
. NOT BURNING ALONE.
We will observe
It startstheburning
formation of gas
with bubblesDAZZLING
a WHITE on the surface of zinc. granules.
FLAME
Pass
Andthe
now gastobeing formed
collect thethrough the soap
Magnesium solution
Oxide taken inhold
Powder a trough (by a
it over
means of a glass delivery tube). Gas filled bubbles are formed in the soap
Watch Glass
solution which rise into the air.
Bring a burning candle near a gas-filled soap bubble. The gas present in soap
bubble burns with a ‘pop’ sound (making a little explosion).
Only hydrogen gas burns making a ‘pop’ sound. This shows that hydrogen gas
is evolved in the reaction of dilute sulphuric acid with zinc metal (taken in the
form of zinc granules)

TEST for CO2 gas

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take a boiling tube and put about 0.5 g of sodium carbonate in it.
Add aboutChalo
2 mLAbof Ise AASAN
dilute BHASHA
hydrochloric acid inMEI Samajhte
the boiling hai : a
tube (through
Take about 2 cm long magnesium ribbon .
thistle funnel)
Clean
We will observe that brisk it with sand
effervescence of a paper.
gas is produced.
HoldPass
the the
magnesium
gas throughribbon with
lime water. Thea lime
pairwater
of tongs , and(showing
turns milky start heating
that it is its
carbon dioxide gas). other end.
Keep on passingThe Magnesiumgas
carbon dioxide through
Ribbon milky lime
starts water for some more
burning.
time. The lime water becomes clear again.
BUT IT'S NOT BURNING ALONE.
This shows that the white precipitate of calcium carbonate dissolves on passing
It starts burning with a WHITE DAZZLING FLAME .
excess of carbon dioxide gas. We can repeat this experiment by using sodium
And now to collect
hydrogencarbonate the
in place ofMagnesium Oxide
sodium carbonate. Powder
Again we willhold it over a
get carbon
dioxide gas which will turn lime waterWatchmilky.Glass
On passing excess of carbon dioxide,
the milky lime water will become clear again.

Activity to investigate whether all compounds containing hydrogen

are acidic.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Chalo
Take Ab Ise 2AASAN
about BHASHA
cm long MEI Samajhte
magnesium hai : .
ribbon
(i) Take solutions of hydrochloric acid, sulphuric acid, glucose and alcohol. All
Clean it with sand paper.
these are hydrogen containing compounds.
Hold the magnesium ribbon with a pair of tongs , and start heating its
(ii) Fix two iron nails on a rubber cork and place the cork in a beaker.(Fig (a) on
next page) other end.
Theto
(iii) Connect the nails Magnesium Ribbon
the two terminals starts
of a 6 burning.
volt battery through a switch and
a bulb. BUT IT'S NOT BURNING ALONE.
It starts
(iv) Pour some dilute burning
hydrochloricwith
acidasolution
WHITE(HClDAZZLING
solution) inFLAME . and
the beaker
Andon
switch now
the to collect
current. The the
bulb Magnesium Oxide
starts glowing.(Fig a) Powder hold it over a
This shows that hydrochloric acid solution
Watch taken
Glassin the beaker conducts electricity.
If we repeat this experiment by taking sulphuric acid solution in the beaker, the
bulb glows again. This shows that sulphuric acid solution also conducts electricity.
In fact, all the acid solutions conduct electricity.
(v) Let us now take glucose solution (C6H12O6 solution) in the beaker and switch
on the current. The bulb does not glow in this case (Fig b). This shows that glucose
solution does not conduct electricity.
If we repeat this experiment by taking alcohol solution in the beaker, the bulb does
not glow again. This shows that alcohol solution also does not conduct electricity.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

Experiment to show that acids do not show acidic behaviour

without water.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.MEI Samajhte hai :
BHASHA
Take about 1 g The
SolidMagnesium
sodium chloride Ribbon
(NaCl) instarts burning.
clean and dry boiling tube and add
conc. sulphuric acid BUT
to it IT'S NOTand
carefully BURNING ALONE.
fit the rubber con over glass tube.
It starts
Conc. sulphuric acidburning with
reacts with a WHITE
Sodium DAZZLING
chloride FLAMEchloride
to form hydrogen . gas.
The hydrogen
And now to chloride
collectgasthestarts coming outOxide
Magnesium of the open
Powderenclave.
hold it over a
Hold a 'dry' blue litmus paper in HCl gas. So there is no change in the colour of dry
Watch Glass
blue litmus paper. This show shows that HCl gas does not behave as an acid to
the absence of water.
We now hold a 'moist' blue litmus paper in HCl gas, Now we will see the 'moist'
blue litmus paper to red. This shows that HCl gas show acidic behaviour in the
presence of water.
Conclusion: HCl gas does not shout acidic behaviour in absence of water but it
shows acidic behaviour in presence of water.

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 Adding Acid/Base in Water
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
Chalo
It starts Ab Ise AASAN
burning with aBHASHA
WHITEMEI Samajhte hai
DAZZLING :
FLAME .
The process of dissolving an acid or a base in water is a highly exothermic one.
And now to collect the Magnesium Oxide Powder hold it over a
Ans-
Watch Glass
i. Yes beaker becomes hot on adding H2SO4 (Acid)
ii. Exothermic reaction took place.

Determining Family of Salts

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Chalo AbClean it with
Ise AASAN sandMEI
BHASHA paper.
Samajhte hai :
Hold
Ans-the
(i. &magnesium ribbon
ii.) Formulas and with a pair of tongs , and start heating its
identification-
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

iii. Na2SO4, NaCI, NaNO3 and Na2CO3 belong to the family of sodium salts.
K2SO4, Na2SO4, CaSO4, MgSO4, CuSO4 belong to the family of sulphate
salts.
NaCI and KCI belong to the family of chloride salts.

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 pH, Acids and Bases Used

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The
ChaloMagnesium
Ab Ise AASANRibbon
BHASHA starts burning.
MEI Samajhte hai :
Ans- BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

Are the Crystals of Salts really Dry?

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
Chalo Ab Ise AASAN Ribbon
The Magnesium BHASHA MEI Samajhte
starts hai :
burning.
i) Take a tube, add few crystals of copper sulphate and heat it.
BUT IT'S NOT BURNING ALONE.
ii) On heating copper sulphate will start appearing white.
It starts burning with a WHITE DAZZLING FLAME .
iii) Copper sulphate crystals contain water of crystallisation. When heated the
And now
crystals, to collect
this water theand
is removed Magnesium
the salt turnsOxide
white.Powder hold it over a
iv) On adding 2-3 droplets of water,Watch
Copper Glass
sulphate crystals restore its blue
colour.

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 Ch-3: Metals and Non-Metals

Chalo Ab
Metals, in Ise AASAN
their BHASHA
pure state, MEI
have Samajhte
a shining hai :
surface.
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
BUT IT'S NOT BURNING ALONE.
Metals, in their pure state, have a shining surface.
It starts burning with a WHITE DAZZLING FLAME .
So, before rubbing and cleaning with sample paper, metals had less shiny surface.
And
After now to
rubbing andcollect
cleaningthe
withMagnesium Oxide
sand paper, they'll Powder
become morehold
shiny.it over a
Watch Glass

Metals are *generally* hard

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
BUT IT'S NOT BURNING ALONE.
i. Metals like iron, copper, aluminium and magnesium are hard to cut with knife.
It starts
ii. Hold a piece burning
of sodium metalwith a pair
with a WHITE DAZZLING
of tongs, put on a FLAME . We
watch-glass.
And now
observe it cantobecollect
cut easilythe
withMagnesium
a knife. Oxide Powder hold it over a
Watch hard.
iii. We observed that metals are generally GlassThe hardness varies from metal to
metal.

Chalo
Some Abmetals
Ise AASAN BHASHA
can be beatenMEIintoSamajhte
thin sheets hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium
Chalo Ab Ise AASANRibbon
BHASHA MEIstarts burning.
Samajhte hai :
We observed that some BUT IT'Scan
metals NOTbe BURNING ALONE.
beaten into thin sheets. This property is
It starts burning with a WHITE DAZZLING FLAME .
called malleability.
Gold
And now toare
and silver the most
collect themalleable metals Oxide Powder hold it over a
Magnesium
Watch Glass

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 Metals are good conductors of heat and have high melting points

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium
Chalo Ab Ise AASANRibbon starts
BHASHA MEI burning.
Samajhte hai :
BUT IT'S NOT BURNING ALONE.
i. On heating the wire we'll find that the heat from burner will travel in the whole
It starts
wire melting the wax.burning with a WHITE DAZZLING FLAME .
ii. And now to
On melting, pincollect the
will drop. ButMagnesium Oxide
metal wire doesn't Powder
melt becausehold
of highit melting
over a
point of metals. Watch Glass
iii. We observed that metals are good conductors of heat and have high melting
points

Chalo AbMetals
Ise AASANalso BHASHA MEI Samajhte hai :
conduct electricity
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
i. On placing the metalBUT IT'S
in the NOTbetween
circuit BURNING ALONE.
terminals A and B, we find that the
bulb glows. It starts burning with a WHITE DAZZLING FLAME .
ii. And now that
This shows to collect thegood
metals are Magnesium Oxide
conductor of Powder
electricity too. hold it over a
Watch Glass

Most non-metals produce acidic oxides when dissolve in water

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
i. Take a magnesium ribbon and some sulphur powder, Burn the magnesium ribbon:
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
2Mg(s) + 02(g) -> 2MgO(s)
Take about 2 cm long magnesium ribbon .
ii. Collect the ashes formed and dissolve them in water.:
Clean +itH20(I)
MgO(S) with sand paper.
-> Mg(OH)2(aq)
Hold thethe
iii. Testing magnesium ribbon
resultant solution withwith
botharedpair
andof tongs
blue litmus, and start
paper, heating
we find its
it is Basic
Mg(OH)2. other end.
iV. Now burn sulphur The Magnesium
powder. Ribbon
Place a test starts
tube over burning.
the burning sulphur to collect the
fumes produced: BUT IT'S NOT BURNING ALONE.
S(s) + 02(g) -› SO2(g)
It starts burning with a WHITE DAZZLING FLAME .
v. Add some water to the above test tube and shake:
And now to collect the Magnesium Oxide Powder hold it over a
S02(g) + H20(1) - H2S03 (aq)
vi. Testing this solution with blue andWatch Glass
red litmus paper, it is acidic Sulphuric Acid,
H2SO3.

What happens when Metals are burnt in Air

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Chalo Ab Clean it with
Ise AASAN sandMEI
BHASHA paper.
Samajhte hai :
Hold thethe
i. Collect magnesium ribbonmetals
samples of following with a– pair of tongs
aluminium, copper,, and
iron,start
lead, heating its
magnesium,
zinc and sodium. other end.
ii. Hold samples with a pair
The of tongs andRibbon
Magnesium try burning over burning.
starts a flame.
eg- 2Mg(s) +BUT
02(g)IT'S
-> 2MgO(s). --We'll getALONE.
NOT BURNING metal oxide as product
iii. Which metals burn easily- Sodium.
It starts burning with a WHITE DAZZLING FLAME .
iv. What flame colour did you observe when the metal burnt?- Yellow
And now to collect the Magnesium Oxide Powder hold it over a
v. How does the metal surface appear after burning?- Silver white
Watch order
vi. Arrange the metals in the decreasing Glassof their reactivity towards oxygen-
Na > Mg > Al > Zn > Fe > Pb > Cu
vii. Are the products soluble in water?- Sodium oxide is soluble in water. Other metal
oxides are insoluble.
viii. We have observed in Activity 3.9 that all metals do not react with oxygen at the
same rate. Different metals show different reactivities towards oxygen

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 Reaction of metals with Steam

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

A lump of glass wool soaked in water is placed at bottom of tube. The water
in glassChalo Ab
wool will Isesteam
form AASAN BHASHA
on heating . MEI Samajhte hai :
The SampleTake about
of metals 2 cm
placed long
in the magnesium
middle ribbonkept
of the horizontally . boiling
tube. The boiling tube Clean it with
containing sand
water, soakedpaper.
glass wool and metal sample
Holdisthe magnesium
arranged ribbon with a pair of tongs , and start heating its
in apparatus.
To start the experiment, the metal sample
other end. is heated by using a burner when
the metal getsThe hot,Magnesium
then the glass Ribbon
wool is heated
startsbyburning.
using other burner.
The water present in glass wool forms steam on heating . This steam then
BUT IT'S NOT BURNING ALONE.
passes over the hot metal. The metal react with steam to form the metal oxide
It starts burning with a WHITE DAZZLING FLAME .
and H2 gas.
And
The nowH2 gastocome
collect the
out of theMagnesium
boiling tube andOxide Powderover
it is collected hold it over
water whenaa
lighted match stick is applied Watch Glass jar, the gas burns with a "pop"
to gas collected
sound, indicating that it is hydrogen. The metal oxide formed remains behind
in the boiling tube.
This experiment is performed by taking magnesium, aluminium, zinc and iron as
metal sample.
It is found that the reaction of steam with magnesium is most vigorous
followed by reaction with aluminium and zine but reaction with iron is slowest.
Magnesium is very reactive whereas the iron is least reactive.
Decreasing order Mg › Al › Zn > Fe
Metals like lead, silver and gold do not react with water or even steam.
Only those metals displace hydrogen from water which are hydrogen in the
reactivity series.

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 What happens when Metals react with Acids?

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

i. Which metals reacted vigorously with dilute hydrochloric acid?
Magnesium shows fastest reaction and hydrogen bubble formation.
ii. With which metal did you record the highest temperature?
Magnesium.
iii. Arrange the metals in the decreasing order of reactivity with dilute acids.
Mg > Al > Zn > Fe.

How do Metals react with Solutions of other Metal Salts?

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

i. Put a clean copper wire and put it in a solution of iron sulphate.
ii. Put a clean iron nail in a solution of copper sulphate.
iii. After 20 minutes, it is observed that blue CuSO4 solution turns green.
iv. In which test tube did you find that a reaction has occurred? -- Test tube
containing CuSO4 solution.
v. On what basis can you say that a reaction has actually taken place? -- The blue
colour of CuSO starts fading.
vi. Can you correlate your observations for the Activities 3.9, 3.10 and 3.11? -- Yes.
In those activities, it is found that Iron is more reactive than copper. It displaces
Cu from CuSO4 to form FeS04.
vii. Write a balanced chemical equation for the reaction that has taken place.
Fe(s) + CuSO4(aq) - FeSO4(aq) + Cu(s)
viii.This is a displacement reaction. ie., reactive metals displace less reactive metals
from their compounds in solution or molten form.

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 CORROSION

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Observations after leaving them for a few days:
i. The iron nails rust in test tube A, but they do not rust in test tubes B and C, because;
ii. In test tube A, the nails are exposed to both air and water.
iii. In test tube B, the nails are exposed to only water.
iv. The nails in test tube C are exposed to dry air.
v. This shows that both air and moisture are needed for rusting of iron.

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 Ch-4: CARBON

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

The atomic mass of C = 12 u, H = 1 u and O = 16 u.
So, molecular mass of CH3OH = 12 + 3 × 1 + 16 + 1 = 32 u.
The molecular mass of C2H5OH = 12× 2 + 5 × 1 + 16 + 1 = 46 u.
The molecular mass of C3H7OH = 12 × 3 + 7 × 1 + 16 + 1 = 60 u.
And molecular mass of C4H9OH = 12 × 4 + 9 × 1 + 16 + 1 = 74 u.
(a) The difference in the molecular formulae of CH3OH and C2H5OH is CH2. The
difference in the molecular masses of CH3OH and C2H5OH is 46 – 32 = 14 u.
(b) The difference in the molecular formulae of C2H5OH and C3H7OH is CH2. And the
difference in the molecular masses of C2H5OH and C3H7OH is 60 – 46 = 14 u.
(c) The difference in the molecular formulae of C3H7OH and C4H9OH is CH2. And the
difference in the molecular masses of C3H7OH and C4H9OH is 74 – 60 = 14 u.

(i) Yes, there is a similarity in the difference between their molecular formulae and
molecular masses. Their molecular formulae differ by CH2 (1 carbon atom and 2
hydrogen atoms), and their molecular masses differ by 14 u.

(ii) These alcohols can be arranged in the order of the increasing carbon atoms as
follows : CH3OH, C2H5OH, C3H7OH, C4H9OH
Yes, we can call it a homologous series.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

NOTE: Saturated hydrocarbons will generally give a clean flame while unsaturated
carbon compounds will give a yellow flame with lots of black smoke. Now,
• Camphor & Naphthalene are unsaturated hydrocarbons. So they burn with yellow
flame and leave residues.
• Alcohol is saturated and burns with clean blue flame.
This results in a sooty deposit on the metal plate

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Limiting the supply of air results in incomplete combustion of even saturated
hydrocarbons giving a sooty flame
When do you get a flame? - In presence of a sufficient supply of air with oxygen, it
gives a blue flame.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

i. When KMnO4 is added, its purple colour disappears initially.

ii. Why does the colour of potassium permanganate not disappear when excess
is added? -- Because all the alcohol gets consumed and the reaction stops.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

i. We observed a product (Sodium ethoxide) with hydrogen gas.

ii. How will you test the gas evolved? -- When a burning spitter is brought near to the
gas, the gas burns with pop sound.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
This is esterification reaction,

Product obtained is ester, having sweet smell.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Foam is formed with difficulty and an insoluble substance (scum) remains after washing
with water. This is caused by the reaction of soap with the calcium and magnesium
salts, which cause the hardness of water. Hence you need to use a larger amount of
soap. This problem is overcome by using another class of compounds called detergents
as cleansing agents.
In which test tube do you get more foam?- Distilled water test tube.
In which test tube do you observe a white curdy precipitate?- Hard water test
tube.
Do both test tubes have the same amount of foam?- No. The test tube containing
detergent has more foam.
In which test tube is a curdy solid formed? -- In the test tube containing soap.

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 Ch-5: Life Processes
Activity to demonstrate that Chlorophyll is necessary for
Photosynthesis

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take a potted plant with variegated leaves – for example, money plant or
crotons.
Keep the plant in a dark room for three days so that all the starch gets used
up. Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Now keep the plant
Take in sunlight
about 2 cm forlong
about six hours.
magnesium ribbon .
Pluck a leaf from the plant.
Clean it with sand paper. and trace them on a
Mark the green areas in it
sheet of paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Dip the leaf in boiling water for a few minutes.
other end.
After this, immerse it in a beaker containing alcohol.
Carefully place ThetheMagnesium
above beaker Ribbon startsand
in a water-bath burning.
heat till the alcohol
begins to boil. BUT IT'S NOT BURNING ALONE.
Now dipIt the
starts
leaf burning
in a dilute with a WHITE
solution of iodineDAZZLING FLAME .
for a few minutes.
And
Takenow
out theto leaf
collect the off
and rinse Magnesium Oxide Powder hold it over a
the iodine solution.
Observe the colour of the leafWatchand compare
Glassthis with the tracing of the leaf
done in the beginning .

Question 1. What happens to the colour of the leaf? What is the colour of the
solution?
Answer. The green leaf becomes colourless. On immersing green leaf in a alcohol,
chlorophyll responsible for its green colour gets dissolves in alcohol. The colour of
the alcohol solution turns green

Question 2. What can you conclude about the presence of starch in various
areas of the leaf?
Answer. The green areas of leaf, which turns dark blue on dipping in iodine
solution, indicate the presence of starch where as colorless part of leaf show no
formation of starch. From this activity we can conclude that chlorophyll is essential
for photosynthesis

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 Activity to show that amount of Carbon Dioxide (CO2), essentially
affects the process and outcome of Photosynthesis

ChaloChalo
Ab Ise AASAN
Ab Ise AASANBHASHA
BHASHA MEIMEI Samajhte
Samajhte hai : hai :
Take potted
Take two healthy aboutplants
2 cmwhichlong are
magnesium ribbon
nearly the same size..
Keep them in a dark roomClean for it with
three sand paper.
days.
Hold the magnesium ribbon with a pairplates.
Now place each plant on separate glass Place,aand
of tongs watch-glass
start heating its
containing potassium hydroxide by the side of one of the plants. The
other end.
potassium hydroxide is used to absorb carbon dioxide.
The Magnesium Ribbon starts burning.
Cover both plants with separate bell-jars as shown in Fig. .
BUT IT'S NOT BURNING ALONE.
Use Vaseline to seal the bottom of the jars to the glass plates so that the set-
It starts burning with a WHITE DAZZLING FLAME .
up is air-tight.
And now
Keep the to collect
plants the Magnesium
in sunlight Oxide Powder hold it over a
for about two hours.
Pluck a leaf from each plant and WatchcheckGlass
for the presence of starch as in the
above activity.

Question 1. Do both the leaves show the presence of the same amount of
starch?
Answer. No, both the leaves do not show the presence of the same amount of
starch, because in photosynthesis starch is produced using sun light, chlorophyll
and CO2. In first set up availability of CO2 will be less for making starch by the
plant leaves, as potassium hydroxide (KOH ) absorb the CO2. In second plant
setup, the leaves will have more amount of starch.

Question 2. What can you conclude from this activity?

Answer. From this activity, we can conclude that amount of Carbon Dioxide (CO2)
, essentially affects the process and outcome of photosynthesis.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.MEI Samajhte hai :
BHASHA
Thesolution
Take 1 mL starch Magnesium Ribbon
(1%) in two starts
test tubes burning.
(A and B).
Add 1 mL saliva toBUT IT'S ANOT
test tube BURNING
and leave ALONE.
both test tubes undisturbed for 20-30
It starts burning with a WHITE DAZZLING FLAME .
minutes.
And
Nownow
add a tofew
collect the
drops of Magnesium
dilute Oxide
iodine solution Powder
to the hold it over a
test tubes.
Question 1. In which test tube doWatchyou observe
Glass a colour change?
Answer. We will observe a colour change in test tube B, showing presence of
starch. Where as test tube A will show no colour change as due to addition of
saliva, starch is converted into sugar.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take some freshly prepared limeother
waterend.
in a test tube.
The this
Blow air through Magnesium
lime water. Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
QuestionIt1.starts burning
Note how long it with
takesafor
WHITE
the limeDAZZLING
water to turnFLAME
milky?.
Answer.
And now Whentowe blow air
collect through
the mouth, theOxide
Magnesium lime water in testhold
Powder tube it
turns milky
over a
within no time. Use a syringe or pichkari to
Watch Glasspass air through some fresh lime water
taken in another test tube.

Question 2. Note how long it takes for this lime water to turn milky?
Answer. When we use syringe or pichkari, to pass air through the lime solution, it
takes much time and effort to turn the lime water milky.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Chalo AbClean it with
Ise AASAN sand MEI
BHASHA paper.
Samajhte hai :
Hold the
Takemagnesium ribbon
some fruit juice with
or sugar a pair
solution andof tongs
add some ,yeast
and tostart
this. heating
Take this its
other
mixture in a test tube fitted with end. cork.
a one-holed
Fit the cork The
with aMagnesium
bent glass tube. Dip thestarts
Ribbon free end of the glass tube into a
burning.
test tube containing
BUTfreshly prepared
IT'S NOT lime water.
BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
Question 1. What change is observed in the lime water and how long does it
And now to collect the Magnesium Oxide Powder hold it over a
take for this change to occur?
Answer. The lime water becomesWatch milky asGlass
carbon dioxide is produced by mixing
yeast in sugar along with alcohol. Time taken for this change to occur, should be
observed by students themselves.
Question 2. What does this tell us about the products of fermentation?
Answer.The products of fermentation are alcohol and carbon dioxide.

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 Ch-6: Control & Coordination

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Have the old parts of BUT
the IT'S
shootNOT
and BURNING
root changedALONE.
direction?
Answer: TheIt starts
old partsburning with
of the shoot a WHITE
and root haveDAZZLING FLAME
no noticeable change. in
And now to collect the Magnesium Oxide Powder hold it over a
direction.
Watch Glass
Are there differences in the direction of the new growth?
Answer: New growth parts show change in direction. i.e., shoot bends towards
light and roots bend away from it.

What can we conclude from this activity?

Answer: Shoots show phototropism and the roots show geotropism.

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 Ch-7: Reproduction

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean
Activity Observation: Under the it with sandwepaper.
microscope, see yeast reproducing by
Hold thebuds.
forming magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning
Activity Observation: A whitewith a WHITE
cottony DAZZLING
mass appears FLAMEof. moist
on the surface
Andwhich
bread now turns
to collect the Magnesium
black within Oxide
few days. The white Powder
cottony masshold
is dueittoover a
growth
Watch
of bread mould (Rhizopus). The spores Glassare present in the air. They settle
of fungus
on the moist bread and germinate to form white cottony mass of vegetative
mycelium. The vegetative mycelium develops asexual sporangia which are black in
colour. Each sporangium contains hundreds of minute black- coloured spores.
These spores are dispersed in air to germinate on suitable substratum

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Activity Observation: Spirogyra, simply breaks up into smaller pieces upon
Clean it with sand paper.
maturation. These pieces or fragments grow into new individuals
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

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Activity Observation: The potato pieces having buds gradually grows and
develops. But there is no growth and development in potato pieces without buds.

Which are the potato pieces that give rise to fresh green shoots and roots?
The pieces with buds give rise to fresh green shoots and roots.

Activity Observation: Portion of Money plant with at least one leaf grows and
gives rise to fresh leaves. But money plant without leaf dies.

What can you conclude from your observations?

Money plant with green leaves can synthesize food through photosynthesis and
able to grow into a plant, through vegetative propagation.

Activity Observation: Two seed cotyledons are separated by radicle and plumule
formation.

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 Ch-9- Light: Reflection & Refraction

Chalo AbAb
Chalo Ise
IseAASAN BHASHA
AASAN BHASHA MEIMEI Samajhte
Samajhte hai : hai :
Take of
The curved surface about 2 cm
a shining longcould
spoon magnesium ribbon
be considered .
as a curved mirror.
One Convex surface and Clean
other it with sand
concave paper.
surface. Sp for answering the
Holdquestions keep in mindribbon
the magnesium the properties
with aofpair
bothof
thetongs
spherical mirrors.
, and start heating its
Question 1: Do you get the image?other Is it smaller
end. or larger?
Yes. The image on the outer curved surface is smaller.
The Magnesium Ribbon starts burning.
Question 2: Move the spoon slowly away from your face. Observe the image.
How does it change?
BUT IT'S NOT BURNING ALONE.
It starts
The size of the burningdecreases.
image gradually with a WHITE DAZZLING FLAME .
And now
Question to collect
3: n Reverse the Magnesium
the spoon and repeat the Oxide Powder
Activity. How hold it over a
does the
image look like now? Watch Glass
The image at its concave side is real, inverted and diminished.
Question 4: Compare the characteristics of the image on the two surfaces.
• The image at its concave side is real, inverted and diminished. If the spoon is
moved away, the image becomes smaller.
• Image at the convex side is virtual, erect & diminished. If the spoon is moved
away, the image becomes smaller.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.MEI Samajhte hai :
BHASHA
The paper atThe
first begins to burn producing
Magnesium smoke. burning.
Ribbon starts Eventually it may even
catch fire.
BUT IT'S NOT BURNING ALONE.
Why does it burn? The light from the Sun is converged at a point, as a sharp,
It starts burning with a WHITE DAZZLING FLAME .
bright spot by the mirror. In fact, this spot of light is the image of the Sun on
And
the now
sheetto
of collect the
paper. This Magnesium
point is the focus Oxide Powder
of the concave hold it over a
mirror.
The heat produced due to theWatch Glass of sunlight ignites the paper. The
concentration
distance of this image from the position of the mirror gives the approximate
value of focal length of the mirror
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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.MEI Samajhte hai :
BHASHA
This activity isThe Magnesium
basically to find outRibbon starts
the positions burning.
of the image formed by the
concave mirrors, their
BUTnature, size etc.
IT'S NOT BURNING ALONE.
You will see in the above Activity
It starts burning with a WHITE that the nature, position FLAME
DAZZLING and size of
. the
image formed by a concave mirror depends on the position of the object in
And now to collect the Magnesium Oxide Powder hold it over a
relation to points P, F and C.
Watch Glass
The image formed is real for some positions, nd virtual for other.
The image is either magnified, reduced or has the same size, depending on
the position of the object.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
This activity is basically to find out the positions of the image formed by the
Take about 2 cm long magnesium ribbon .
convex mirrors, their nature, size etc.
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
Question 1: Observe the image of the pencil in the mirror. Is the image erect
And now to collect the Magnesium Oxide Powder hold it over a
or inverted? Is it diminished or enlarged?
Watch Glass
Its image in the mirror is erect and diminished.
Question 2: Move the pencil away from the mirror slowly. Does the image
become smaller or larger?
The image becomes smaller.
Question 3: Repeat this Activity carefully. State whether the image will move
closer to or farther away from the focus as the object is moved away from
the mirror?
The image moves closer to the focus.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASAN other end.MEI Samajhte hai :
BHASHA
This activity isThe Magnesium
basically to find outRibbon
which of starts burning.
these mirrors will give the full
image of a large BUTobject?IT'S NOT BURNING ALONE.
Observation: You can see a full-length image of a tall building/tree in a
It starts burning with a WHITE DAZZLING FLAME .
small convex mirror. One such mirror is fitted in a wall of Agra Fort facing Taj
And now to collect the Magnesium Oxide Powder hold it over a
Mahal.
Watch Glass

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Chalo
Take Ab Ise 2AASAN
about cm longBHASHA MEI Samajhte
magnesium hai : .
ribbon
These activities are toClean
understand the sand
it with phenomenon
paper.of refraction of light.
Light does not travel in the same direction in all media. It appears that when
Hold the magnesium ribbon with a pair of tongs , and start heating its
travelling obliquely from one medium to another, the direction of propagation
other end.
of light in the second medium changes.
The Magnesium Ribbon starts burning.
Question 1: With your BUT
eye IT'S NOTabove
to a side BURNING
water,ALONE.
try to pick up the coin in one
go. Did youIt succeed
starts burning
in picking with a WHITE
up the coin? DAZZLING FLAME .
NoAnd now to collect the Magnesium Oxide Powder hold it over a
Question 2: Repeat the Activity.Watch Why didGlass
you not succeed in doing it in one
go?
Reflected light coming from the submerged coin in water (denser medium), on
entering air (rarer medium), bend away from the normal due to refraction of light
and image size becomes larger than its actual size. Thus, coin appears to be
closer than its actual distance.
Question 3: Keep looking for the coin from your position. Does the coin
becomes visible again from your position? How could this happen?
Yes. The coin becomes visible again. This is because the coin appears slightly
raised above its actual point due to refraction of light.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Draw a thick straight line in ink, over a sheet of white paper on a table.
Place a glass slab over the line in such a way that one of its edges makes an
angle with the line.

Question: Look at the portion of the line under the slab from the sides.
What do Chalo Ab Ise AASAN
you observe? Does theBHASHA
line underMEI Samajhte
the glass hai : to be
slab appear
bent at theTake
edges?about 2 cm
-- Yes, long
the line magnesium
under ribbon
the slab appears . bent and it
to be
is due to refraction. Clean it with sand paper.
Next, place the glass slab such that it is normal to the line.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch
Question: What do you observe Glass
now? Does the part of the line under the
glass slab appear bent? -- No, the part of the line under the glass slab does
not appear bent because the ray of light is perpendicular to the slab and does
not make any angle, so it appears straight.
OBSERVATION: This activity demonstrates the phenomenon of refraction and
for normal incidence, there no refraction occurs.
Question: Look at the line from the top of the glass slab. Does the part of
the line beneath the slab, appear to be raised? why does this happen? --
Yes, the part of the line beneath the slab appears to be raised because of
refraction.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium Oxide Powder hold it over a
Watch Glass

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
These activities
TheareMagnesium
to understandRibbon
the phenomenon of refraction of light
starts burning.
through glass slab.
BUT IT'S NOT BURNING ALONE.
Here, the light ray has changed its direction at points O and O'. Both the
It starts burning with a WHITE DAZZLING FLAME .
points O and O' lie on
And
The now to at
light ray collect
point Othe Magnesium
enters from a rarerOxide
mediumPowder
(air) to ahold
denseritmedium
over a
(glass). The light ray Watch Glass
Compare the angle of incidence with angle of refraction at both refracting
surfaces AB & CD. A ray EO is obliquely incident on surface AB, called
incident ray.
OO′ is the refracted ray and O′ H is the emergent ray. You may observe that
the emergent ray is parallel to the direction of the incident ray.
Why does it happen so? The
However, the light ray is shifted sideward slightly.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
Chalo Ab Ise AASANother end.MEI Samajhte hai :
BHASHA
The to
The paper begins Magnesium
burn producingRibbon
smoke.starts burning.
It may even catch fire after a
while. BUT IT'S NOT BURNING ALONE.
It starts
Why does burning
this happen? The with a WHITE
light from the SunDAZZLING FLAMErays
constitutes parallel . of light.
These
And nowraysto
were converged
collect by the lens at the
the Magnesium Oxidesharp bright spot
Powder formed
hold on the
it over a
paper. In fact, the bright spot you got on the paper is a real image of the Sun.
Watch Glass
The concentration of the sunlight at a point generated heat. This caused the
paper to burn.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
This activity is basically to find out the positions of the image formed by the
convex lens, their nature, size etc.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

This activity is basically to find out the positions of the image formed by the
concave lens, their nature, size etc.

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 Ch-12- Electricity

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Chalo AbClean
Ise AASAN BHASHA
it with sandMEI Samajhte hai :
paper.
This activity is basically for obtaining V-I graph (Ohm's Law).
Hold the magnesium ribbon with a pair of tongs , and start heating its
First, only one cell is the voltage source, note down the ammeter and
other end.
voltmeter readings and fill in the table provided.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
It starts burning with a WHITE DAZZLING FLAME .
And now to collect the Magnesium i1 v1
Oxide Powder v1/i1
hold it over a
i2 v2 v2/i2
i3Watch Glassv3 v3/i3
i4 v4 v4/i4

We observed that approximately the same value for V/I is obtained in each
case. Thus the V–I graph is a straight line that passes through the origin of the
graph, as shown in Fig. 12.3. Thus, V/I is a constant ratio.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
BUT IT'S
This activity is basically NOT
to study BURNING
about electricalALONE.
resistance of a conductor.
It starts burning with a WHITE DAZZLING FLAME .
In this Activity we observe that the current is different for different
And
Whynow to differ?
do they collect the Magnesium
Certain Oxide
components offer Powder
an easy hold
path for theitflow
over
of a
Watch
electrical current while the others resistGlass
the flow.
We know that the motion of electrons in an electric circuit constitutes an
electric current. The electrons, however are not completely free to move within
a conductor. They are restrained by the attraction of the atoms among which
they move.
Thus, motion of electrons through a conductor is retarded by its resistance.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

This activity is basically to find out factors on which resistance of a conductor
depends.
We know, Answering the questions keeping in mind this only.
Question: Does the current depend on the length of the conductor? - Yes
Question: Does the current depend on the area of cross-section of the wire
used? - Yes

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
This activity is basically to understand that the current in the ammeter is the
same, independent of its position in the electric circuit.
It means that in a series combination of resistors the current is the same in
every part of the circuit or the same current through each resistor.

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

This activity is basically to understand that the potential difference V is equal
to the sum of potential differences V1 , V2 , and V3 .
That is the total potential difference across a combination of resistors in series
is equal to the sum of potential difference across the individual resistors.
V = V1 + V2 + V3

*Activity 12.6 is derivation of equivalent resistance formula for parallel.

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 Ch-13- Magnetic Effects

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
BUT IT'S NOT BURNING ALONE.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
It starts burning with a WHITE DAZZLING FLAME .
We see that the needle is deflected which means that the electric current through
And
the nowwire
copper to has
collect the Magnesium
produced Oxide
a magnetic effect. ThusPowder hold
we can say thatitelectricity
over a
and magnetism are linked to eachWatch
other Glass

Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :

Take about 2 cm long magnesium ribbon .
Clean it with sand paper.
Hold the magnesium ribbon with a pair of tongs , and start heating its
other end.
The Magnesium Ribbon starts burning.
Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
BUT IT'S NOT BURNING ALONE.
The magnet exerts its influence in the region surrounding it. Therefore the iron
It starts
filings experience burning
a force. with thus
The force a WHITE
exertedDAZZLING FLAME
makes iron filings .
to arrange in a
And now to collect
pattern(Fig-13.2). the
The region Magnesium
surrounding OxideinPowder
a magnet, which thehold
force it
of over
the a
magnet can be detected, is said to Watch
have aGlass
magnetic field. The lines along which
the iron filings align themselves represent magnetic field lines.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
We shall first consider the pattern of the magnetic field around a straight conductor
carrying current.
What happens to the deflection of the compass needle placed at a given point if the
current in the copper wire is changed? To see this, vary the current in the wire. We find
that the deflection in the needle also changes. In fact, if the current is increased, the
deflection also increases. It indicates that the magnitude of the magnetic field produced
at a given point increases as the current through the wire increases.
What happens to the deflection of the needle if the compass is moved away from
the copper wire but the current through the wire remains the same? To see this, now
place the compass at a farther point from the conducting wire (say at point Q).
What change do you observe? We see that the deflection in the needle decreases. Thus
the magnetic field produced by a given current in the conductor decreases as the
distance from it increases.
From Fig. 13.6, it can be noticed that the concentric circles representing the magnetic field
around a current-carrying straight wire become larger and larger as we move away from
it.
Does the direction of magnetic field lines get reversed if the direction of current
through the straight copper wire is reversed? -- The direction of magnetic field lines is
reversed if the direction of current through the copper wire is reversed.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
The displacement of the rod (AB) suggests that:
A force is exerted on the current-carrying aluminium rod when it is placed in a
magnetic field.
The direction of force is also reversed when the direction of current through the
conductor is reversed.

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If the south pole of the magnet is moved towards the end B, the deflections in the
galvanometer would just be opposite to the previous case.
When the coil & magnet are stationary, there is no deflection in the galvanometer.
This activity shows that the motion of a magnet with respect to the coil produces an
induced potential difference, which sets up an induced electric current in the circuit.

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 Chalo Ab Ise AASAN BHASHA MEI Samajhte hai :
As soon as the current in coil-1 reaches either a steady value or zero, the
galvanometer in coil-2 shows no deflection.
We conclude that a potential difference is induced in coil-2 whenever the electric
current through the coil-1 is changing (starting or stopping). Coil-1 is called the
primary coil and coil-2 is called the secondary coil. As the current in the first coil
changes, the magnetic field associated with it also changes. Thus the magnetic field
lines around the secondary coil also change. Hence the change in magnetic field
lines associated with the secondary coil is the cause of induced electric current in it.
This process, by which a changing magnetic field in a conductor induces a current in
another conductor, is called electromagnetic induction

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