Download CLASS 10th sci sa-1 qb 2016-17

2014-15 & 2015-16 QUESTION
PAPERS WITH SOLUTIONS
SECTION-A ( 1 mark questions)
1)Why does the colour of copper sulphate solution change
when an iron nail is dipped in it?
ANS: Since iron displaces copper from copper sulphate
solution.
2)Name the term for transport of food from leaves to other
parts of the plant.
ANS: Translocation.
3)Name the radiation responsible for heating effect.
ANS: Infrared radiation.
4)In the reaction represented by the following equation:
CuO(s) + H2 -> Cu(s) + H2O(l)
a)Name the substance oxidized.
b)Name the substance reduced.
ANS: a) H2 is oxidized to H20
b)CuO is reduced to Cu.
5)Nichrome is used to make the element of electric heater
why?
ANS: High resistivity, do not oxidize at high temperature.
6)Write two disadvantages of fossil fuels.
ANS: Pollution, Acid rain, Global warming, Nonrenewable
energy.
SECTION-B ( 2 mark questions)
7)Write one equation each for decomposition reactions
where energy is supplied in the form of (i) heat, (ii)light.
ANS: (i) 2Pb(NO3)2(s) ->2PbO(s)+4NO2(g)+O2(g)
(ii) 2AgCl(s) ->2Ag(s)+Cl2(g)
8)Diagrammatically show the mode of nutrition in amoeba.
ANS: Four stages of correct diagram refer page no. 98 in
NCERT textbook.
9)List out the factors in which the resistance of a conductor
depends.
ANS:
Length, Area, Resistivity of the conductor and
temperature.
10)What happens when silver chloride is exposed to
sunlight? Write a chemical equation for the reaction. Also
give one use of such reaction.
ANS: Decomposes to form silver and chlorine gas.
2AgCl(s) ->2Ag(s)+Cl2(g) ; used in black and white
photography.
11)An electric motor takes 5 A from a 220 V line. Determine
the power of the motor and the energy consumed in 2 hrs.
ANS: P=VI,V=220V,I=5A ;220x5=1100 W (1)
E=Pt,P=1100W,t=2 hrs.
E=1100x7200s=7.92x10^6 J.
12) How are fats digested in our body ? Where does this
process takes place ?
ANS: Bile salts break fats into small globules and make it
easy for digestion, and the process is called emulsification.
Small intestine
13)(i) What do you observe when solution of Potassium
Iodide is added to a solution of Lead Nitrate taken in a test
tube?
(ii) What type of reaction is this?
(iii) Write balanced chemical equations to represent the
above reaction.
ANS:(i) Yellow colour precipitate is formed.
(ii) Double displacement reaction.
(iii) Pb(NO3)2+2KI->PbI2+2KNO3
14)(i) Write the chemical name of baking soda.
(ii) What is baking powder? How does make the cake soft
and spongy?
ANS: (i) Sodium Hydrogen Carbonate, NaHCO3
(ii) Baking powder is a mixture of baking soda and an
edible acid like tartaric acid. Baking powder on heating
produces carbon dioxide gas which makes bread or cake soft
and spongy.
15)Name the three products obtained on electrolysis of an
aqueous solution of sodium chloride. Write the chemical
reaction involved. Why is this called chlor-alkali process?
ANS: Sodium Hydroxide, chlorine and hydrogen gas.
2NaCl + 2H2O -> 2NaOH + Cl2 + H2
Because of the product formed – chlor for chlorine and
alkali for sodium hydroxide.
16)a)Diagrammatically show the formation of NaCl from
sodium and chlorine atoms.
b)Why does sodium chloride have high melting point?
ANS:a) Refer NCERT text book. Page no. 47.
b)Sodium and Chlorine ions, being oppositely charged,
attract each other and are held by strong electrostatic force of attraction.
17)What is meant by corrosion? Name any three methods
used for the prevention of corrosion.
ANS:The surface of some metals, such as iron, is corroded
when they are exposed to moist for a long period of time.
This phenomenon is called corrosion.
The rusting of iron can be prevented by painting, oiling,
greasing, galvanizing, chrome plating, anodizing or making
alloys.
18)What is a tropic movement ? Explain with an example.
ANS: Definition.
Explanation for any one of them ( phototropism,
geotropism, chemotropism & hydrotropism ).
19)a) Why are some alloys commonly used in electric heating
devices?
b) What will be the current drawn by an electric bulb of
40W when it is connected to a source of 220 V .
ANS: a) Resistivity of an alloy is higher.
Does not undergo oxidation easily even at high
temperature.
b) P=VI
I=0.2 A
20)a) Why is a series arrangement not used for domestic
circuit?
b)
50 J of heat is produced each second in a 2 ohm
resistance. Find the potential difference across the resistor.
ANS: a) If one appliance fails, other appliance stops working.
b) H=VIt
V=10V
21) You would have seen at the roofs of the houses,
hospitals, hotels, etc. solar panel for electricity and solar
heaters for hot water are placed. Nowadays many people are
preferring these methods as sources of energy.
a) What kind of source of energy is used here?
b) Why are people preferring these kind of methods?
c) How it will affect our environment?
ANS: a) Renewable/Solar energy.
b) Save electrical energy.
c) Non polluting.
22) What are the qualities of an ideal source of energy?
ANS: High calorific value, Pollution free, Low cost, Easy to
transport.
23) Under what condition does a current carrying conductor
kept in a magnetic field experience maximum force? Name
&state the rule used for the determination of direction of
this force.
ANS: B & V are perpendicular. Fleming’s left hand rule and
correct statement.
24) State the properties of magnetic lines of force.
ANS: Magnetic field lines move from north to south.
Two lines never intersect each other.
Inside the magnet it moves from south to north.
25)Write the balanced chemical equation for the following
and identify the type of reaction in each case.
a) Potassium bromide(aq)+Barium iodide(aq)->Barium
bromide(aq)+Potassium iodide(aq)
b) Hydrogen(g)+Chlorine(g)->Hydrogen chloride(g)
c) Zinc carbonate(s)->Zinc oxide(s)+Carbon dioxide(g)
ANS: a) 2KBr+BaI2->2KI+BaBr2 ( double displacement)
b) H2+Cl2->HCl (combination reaction)
c) ZnCO3->ZnO+CO2 (decomposition reaction)
26)a) Define corrosion. Under what conditions
corrosion take place.
b) Give formula and chemical name of rust.
c) Give two methods to prevent rancidity.
ANS: a) Definition and two conditions.
b) Fe2O3, Ferric(III) Oxide.
c) any two methods.
does
27) a) Why does an aqueous solution of acid conduct
electricity?
b)
How does the concentration ph hydronium ions
change when a solution of an acid is diluted.
c)
Which has a higher pH value, concentrated or
dilute solution of HCl.
ANS: a) Produce hydrogen ions in solution.
b) Decreases.
c) dil.HCl has higher pH value.
28) a) Write the formula and chemical name of bleaching
powder.
b)Write the chemical reaction for its preparation.
c) State any two uses of bleaching powder.
ANS: a) CaOCl2, Calcium oxychloride.
b)Refer NCERT textbook page no.30
c)Any two uses.
29) Give reasons for the following:
a) Aluminium oxide is considered as an amphoteric oxide.
b) Metals donot evolve hydrogen gas with nitric acid.
c) Ionic compounds have high melting point.
ANS: a) Reacts with both acid and base.
b) Nitrogen is acting as an oxidizing agent, oxidizing
hydrogen to water.
c) Ionic bonds are very strong and need high energy to
break the bonds.
30) Three resistors of 6 ohm, 10 ohm and 30 ohm are
connected in parallel to a 6 volt battery then calculate:
a)The value of current through each resistor.
b)The total current in the circuit.
c)The total effective resistance of the circuit.
ANS: a)I1=V/R1=6/5=1.2A
I2=V/R2=6/10=0.6A
I3=V/R3=6/30=0.2A0
b) I=I1+I2+I3=2A
c) Effective resistance = V/I=6/2=3 ohm.
31) Derieve an expression for the combination of two
resistors in series.
ANS: Resistor in series. Refer NCERT textbook pg.211 (3).
32) Explain the following:
a) Why is tungsten used almost exclusively for filament in
electric heater.
b) How does the resistence of a wire vary with its area of
cross section.
c) Why parallel arrangement is preferred over series
arrangement in domestic circuits.
ANS:(a)High resistivity, do not oxidize at high temperature.
(b)Decreases because area of cross section is inversely
proportional to the resistance of the conductor.
(c) Suitable for any appliance because current is different for
different resistors, same voltage, different switches, any
other.
33) What is a solenoid? Draw neat diagram of solenoid and
mention the use of solenoid.
ANS: A coil of many circular turns, of insulated copper wire
wrapped closely in the shape of a cylinder is called solenoid.
Diagram refer text book page no.229.
Used for making electromagnets.
34)a) Draw a neat labeled diagram of reflex arc.
b) List in order the three different neurons involved in a
reflex arc from the stimulus to the response in a proper
order.
ANS: a) Refer text book pg.no 117.
b) Sensory neuron-Relay neuron-Motor neuron.
35) In a village people burn wood and cow dung as fuel for
basic necessity. In another nearby village people have a
biogas plant in which biowaste is used to prepare biogas
which is supplied to all the houses of the village.
a) If we compare the situation of both villages which practice
is the best and why?
b) What values are promoted by each village?
c) Suggest some other ways that can be employed for saving
resources.
ANS: a) The practice of the second village is the best because
they are employing a less polluting and less expensive fuel.
b) The first village is promoting no concern for the
environment. The second village is promoting environmental
concern.
c) Any two values.
36) Write
limitations
ANS: Any
limitations
down 3 limitations of wind energy and 3
of nuclear energy.
three limitations of wind energy;Any three
of nuclear energy.