SCIENCE MOST
IMPORTANT
QUESTIONS
P
CHAPTERWISE
CLASS 10
Solid
calcium oxide was taken in a container and water was added
slowly
to it. (CBSE 2013, 2019)
1.
(a)
Write the observations.
(b)
Write the chemical formula of the product formed.
2.What
change in color is observed when white silver chloride is
left
exposed to sunlight? State the type of chemical reaction in
this
change. (CBSE 2014, 2019, 2023)
3.Write
the chemical equation of the reaction in which the following
changes
take place with an example of each. (CBSE 2023, 2015)
(a)
Change in color (b) Change in temperature
4.
In the electrolysis of water, (CBSE 2020, 2013, SP-2018)
A.
Name of the gases liberated at anode & cathode.
B.
Why is it that the volume of gas collected on one electrode is
two
times that on the other electrode?
C.
What would happen if dilute H S0 is not added to water?
5.
A shining metal ‘M’ on burning gives a dazzling white flame &
changes
to a white powder ‘N’. (CBSE 2020, 2022)
A.
Identify ‘M’ & ‘N’.
B.
Represent the above reaction in the form of a balanced chemical
equation.
C.
Does ‘M’ undergo oxidation or reduction in this reaction? Justify.
SCIENCE
TOP 5 QUESTIONS
Chemical Reactions and Equations
SCIENCE
List
the important products of the chlor-alkali process. Write one
important
use of each. (CBSE 2020, 2023)
1.
2.
(a) Identify the acid and the base whose combination forms the
common
salt that you use in your food. Write its chemical
formula
and chemical name of the salt.
(b)
What is rock salt?
(c)
Mention its color and the reason due to which it has this colour.
(CBSE
2019, 2013)
3.Write
the chemical equations when zinc granules react with:
(a)
Sulphuric acid (b) Hydrochloric acid
(CBSE
2014, 2020)
4.
How is sodium hydroxide produced? Write the balanced chemical
equation
also. Why is this process called the chlor-alkali process?
In
this process name the products given off at:
(a)
anode
(b)
cathode. (CBSE 2022, 2015)
5.
Give the reasons for the following:
(i)
Only one half of water molecule is shown in the formula of
plaster
of Paris. (CBSE 2020, CBSE SP - 2017)
Acids, Bases and Salts
List the important
products of the chlor-alkali process. Write one important use of each. (CBSE
2020, 2023)
1
(a) Identify the acid
and the base whose combination forms the common salt that you use in your food.
Write its chemical formula and chemical name of the salt. (b) What is rock
salt? (c) Mention its color and the reason due to which it has this colour. (CBSE
2019, 2013)
3.Write the chemical equations when zinc
granules react with: (a) Sulphuric acid (b) Hydrochloric acid (CBSE 2014, 2020)
4. How is sodium
hydroxide produced? Write the balanced chemical equation also. Why is this
process called the chlor-alkali process? In this process name the products
given off at: (a) anode (b) cathode. (CBSE 2022, 2015)
5. Give the reasons for
the following: (i) Only one half of water molecule is shown in the formula of
plaster of Paris. (CBSE 2020, CBSE SP - 2017)
Metals and NonI-MetalsCE
1.
Why do ionic compounds conduct electricity in molten state and not
in
solid state? (CBSE 2014, 2023)
2.
The reaction of metal X with Fe O is highly exothermic and is used
to
join railway tracks. Identify metal X. Write the chemical
equation
for the reaction. (CBSE 2016, 2023)
3.
Zinc is a metal found in the middle of the activity series of metals.
In
nature, it is found as a carbonate ore, ZnCO . Mention the steps
carried
out for extraction from the ore. (CBSE 2023, 2013)
4.
Differentiate between roasting and calcination giving chemical
equations
for each. (CBSE 2013, 2023)
5.
Why are copper vessels corroded with a green coating in the rainy
season?
(CBSE 2015, 2016, 2019)
carbon and its compounds CE
1.Draw
the electron dot structure of Nitrogen. (CBSE 2023, 2021)
2.Write
the chemical formula of benzene and draw its structure.
(CBSE
2017, 2021, 2023)
3.
What will you observe on adding a 5% alkaline KMnO solution drop
by
drop to some warm ethanol taken in a test tube? Write the
name
of the compound formed during the above chemical reaction.
(CBSE
2013, 2020)
4.Why
do covalent compounds have low melting and boiling points?
(CBSE
2020, 2021)
5.What
is meant by a homologous series of carbon compounds? Write
the
general formula of (CBSE 2015, 2014, 2016,2019)
(a)
alkenes
(b)
alkynes
Life Process:
(a) What is 1. double circulation?
(b)
Why is the separation of the right side and the left side of
the
heartful useful ? How does it help birds and mammals?
(CBSE
2023, 2022, 2019)
2.Explain
the ways in which glucose is broken down in the absence or
storage
of oxygen? (CBSE 2017, 2018, 2019)
3.
(a) Write two water-conducting tissues present in plants. How
does
water enter continuously into the root xylem?
(b)
Explain why plants have low energy needs as compared to
animals.
(CBSE 2017, 2019, 2021)
4.
In single-celled organisms, diffusion is sufficient to meet all
their
requirements for food, gas exchange, or removal of waste,
but
it is not in the case of multicellular organisms. Explain the
reason
for the difference. (CBSE 2015, 2019, 2022)
5.
Draw a diagram of the human alimentary canal and label the
following:
(CBSE 2016, 2019, 2020)
(1)
part in which starch digestion is initiated
(2)
organ in which bile is stored
(3)
the gland that secretes digestive enzymes as well as hormones.
(4)
Part of the alimentary canal where water is reabsorbed.
(5)
Parts of the gut where finger-like projections are present to
facilitate
absorption of digested food.
Control and coordination
1.
Name a plant hormone responsible for bending of a shoot of a
plant
when it is exposed to unidirectional light. How does it
promote
phototropism ? (CBSE 2019, 2023)
2.
With the help of suitable examples explain the terms
phototropism,
geotropism and chemotropism, (CBSE 2016, 2020)
3.
Draw a diagram of the cross-sectional view of the human brain
label
the parts of the brain with the functions. (CBSE 2017, 2020)
4.
How does the feedback mechanism regulate hormone
secretion?
Explain with the help of an example ? (CBSE 2017, 2019)
5.
Name the part of human brain which control the voluntary and
involuntary
actions. (CBSE 2017, 2018)
How do organisms reproduce?
1.
Difference between the asexual and sexual reproduction ? Also,
give
one example of each. (CBSE 2016, 2018, 2021, 2022)
2.
Describe reproduction by spores in Rhizopus.
(CBSE
2017, 2015, 2020, 2022)
3.
List three techniques that have been developed to prevent
pregnancy.
Which one of these techniques is not meant for males ?
How
does the use of these techniques have a direct impact on the
health
and prosperity of a family ? (CBSE 2017, 2018, 2020)
4.
a. Draw a diagram of human female reproductive system and
label
the parts:
Which
produce an egg, Where fertilization takes place
B.
List two bacterial diseases which are transmitted sexually.
C.
What are contraceptive devices? Give two reasons for
adopting
contraceptive devices in humans.
(CBSE
2019, 2017, 2016)
5.
Define pollination. Explain the different types of pollination. List
two
agents of pollination. How does suitable pollination lead to
fertilization
? (CBSE 2019, 2016, 2021)
2 4
Heredity and Evolution
Mention
any two points of difference between acquired and
inherited
traits. If the tail of a mouse is cut for twenty one
generations,
will the tail occur in the twenty second generation of
that
mouse? Give reason to support your answer.
(CBSE
2013, 2016, 2017, 2022, 2021)
Two
pea plants- one with round yellow seeds (RRYY) and another
with
wrinkled green (rryy) seeds produce F1 progeny that have
round,
yellow (RrYy) seeds. When F1 plants are self-pollinated,
which
new combination of characters is expected in F2 progeny?
How
many seeds with these new combinations of characters will be
produced
when a total 160 seeds are produced in F2 generation?
Explain
with reason. (CBSE 2018, 2020, 2022)
List
difference between dominant traits and recessive traits. What
percentage
of the plants in the F2 generation were round, in
Mendel’s
dihybrid cross between round yellow and wrinkled green
pea
plants ? (CBSE 2016, 2015, 2019)
Sahil
performed an experiment to study the inheritance pattern of
genes.
He crossed tall pea plants (TT) with short pea plants (tt) and
obtained
all tall plants in F1 generation.
a.
What will be the set of genes present in the F1 generation?
b.
Give reason why only tall plants are observed in F1 progeny.
(CBSE
2016, 2021, 2022)
In
an asexually reproducing species, if a trait X exists in 5% of a
population
and trait Y exists in 70% of the same population, which
of
the two traits is likely to have arisen earlier? Give reason.
(CBSE
2019, 2021)
Light
1.State
the two laws of reflection of light.
(CBSE
2011, 2013 2014)
2.The
absolute refractive indices of glass and water are 1.5 and 1.33
respectively.
In which medium does light travel faster? Calculate
the
ratio of speeds of light in the two media.
(CBSE
2013, 2019, 2020)
3.The
image of a candle flame placed at a distance of 30 cm from a
mirror
is formed on a screen placed in front of the mirror at a
distance
of 60 cm from it pole. What is the nature of the mirror?
Find
its focal length. If the height of the flame is 2.4 cm, find the
height
of its image. State whether the image formed is erect or
inverted.
(CBSE 2014, 2015, 2017)
4.
Draw ray diagram to show the path of the refracted ray in each of
the
following cases. A ray of light incident on a concave lens (i) is
parallel
to its principal axis, (ii) is passing through its optical centre
and
(iii) is directed towards its principal focus.
(Delhi
2013, CBSE 2015, 2016)
5.An
object is placed at a distance of 50 cm from a concave lens of
focal
length 30 cm.
(i)
Use lens formula to find the distance of the image from the
lens.
(ii)
List four characteristics of the image(nature, position, size,
erect/inverted)
formed by the lens in this case.
(iii)
Draw a ray diagram to justify your answer of pair (ii).
(CBSE
2016, 2019)
Human eye & colorful world
1.
What is ‘dispersion of white light’? State its cause. Draw a ray
diagram
to show the dispersion of white light by a glass prism.
(CBSE
2011, 2013, 2016, 2017)
2.
How will you use two identical glass prisms so that a narrow beam of
white
light incident on one prism emerges out of the second prism as
white
light? Draw and label the ray diagram.
(CBSE
2016, 2017, 2019, 2020)
3.Draw
a ray diagram to show the refraction of light through a
glass
prism. Mark on it (a) the incident ray, (b) the emergent ray
and
(c) the angle of deviation.
(CBSE
2011, 2013, 2017)
4.
State the function of each of the following parts of human eye:
(i)
Cornea
(ii)
Iris
iii)
Pupil
(CBSE
2013, 2016, 2018)
5.A
student is unable to see clearly the words written on the black
board
placed at a distance of approximately 3 m from him. Name the
defect
of vision the boy is suffering from. State the possible causes
of
this defect and explain the method of correcting it.
(CBSE
2017, 2018)
Electricity
1.
(a) Prove that the equivalent resistance of three resistors R1, R2
and
R3 in series is R1 + R2 + R3.
(b)
You have four resistors of 8 each. Show how would you connect
these
resistors to have effective resistance of 8Ω ?
(2013,
2015, 2016)
2.
State Ohm's law. Draw a labelled circuit diagram to verify this law
in
the laboratory. If you draw a graph between the potential
difference
and current flowing through a metallic conductor, what
kind
of curve will you get? Explain how would you use this graph to
determine
the resistance of the conductor. (2014, 2015, 2016)
3.(i)State
one difference between kilowatt and kilowatt hour. Express
1
kWh in joules.
(ii)
A bulb is rated 5V; 500 mA. Calculate the rated power and
resistance
of the bulb when it glows.
(2013,
2016)
4.
Two lamps, one rated 100 W; 220 V, and the other 60 W; 220 V, are
connected
in parallel to electric mains supply. Find the current drawn
by
two bulbs from the line, if the supply voltage is 220 V.
(2018.
2014)
5.Draw
a schematic diagram of a circuit consisting of a battery of 3
cells
of 2 V each, a combination of three resistors of 10Ω, 20Ω and
30Ω
connected in parallel, a plug key and an ammeter, all connected in
series.
Use this circuit to find the value of the following:
(a)
Current through each resistor
(b)
Total current in the circuit
(c)
Total effective resistance of the circuit. (2020)
Magnetic effects of current
1.
State whether an alpha particle will experience any force in a
magnetic
field if (alpha particles are positively charged particles) (i) it
is
placed in the field at rest.
(ii)
it moves in the magnetic field parallel to field lines.
(iii)
it moves in the magnetic field perpendicular to field lines. Justify
your
your answer in each case.
(CBSE
2016, 2022, 2023)
2.
Mention and explain the function of an earth wire. Why it is
necessary
to earth metallic appliances? (CBSE 2014, 2016, 2020)
3.
Name and state the rule which is used to determine the
direction
of force on a current carrying conductor placed in a
magnetic
field. (CBSE 2020, 2022, 2023)
4.
What are magnetic field lines? Justify the following statements:
(a)
Two magnetic field lines never intersect each other.
(b)
Magnetic field are closed curves. (CBSE 2013, 2015, 2016)
5.
What is solenoid? Draw the pattern of magnetic field lines of
(i)
a current carrying solenoid and
(ii)
a bar magnet.
List
two distinguishing features between the two fields.
(Delhi
2019, 2020)
Our Environment
1.
How is ozone formed in the higher levels of the atmosphere? “
Damage
to the ozone layer is a cause of concern”. Justify this
statement.
(CBSE 2015, 2017, 2020, 2023)
2.
We do not clean ponds or lakes, but an aquarium needs to be
cleaned
regularly. Explain. (CBSE 2023, 2017)
3.
Why are green plants called the producers ?
(CBSE
2019, 2015)
4.
(a) How can we help in reducing the problem of waste disposal?
Suggest
any three methods.
(b)
Distinguish between biodegradable and non-biodegradable wastes.
(CBSE
2013, 2015, 2019)
5.
Define an ecosystem. Draw a block diagram to show the flow of
energy
on an ecosystem. (CBSE 2015, 2017, 2019)
Solutions
Chemical Reactions and Equations
1.
(i) Following are the two observations:
Calcium
oxide reacts vigorously with water to form slaked lime.
The
container becomes hot because a large amount of heat is
released
during this reaction.
(ii)
The product formed is slaked lime for which the chemical
formula
is Ca(OH) .
2.
When white silver chloride exposed to sunlight it produces to black
metallic
coloured silver along with liberation of chlorine gas
2AgCl
2Ag + Cl
it
is photodecomposition reaction.
3.
(i) Change in colour:
The
reaction between lead nitrate solution and potassium iodide
solution.
In
this reaction colour changes from colourless to yellow.
(ii)
Change in temperature:
The
action of dilute sulphuric acid on zinc.
In
this reaction, heat is evolved.
4.
(a) At cathode, H2 is evolved and at anode O2 is evolved.
(b)
At cathode, H+ ion takes two electron to convert itself into H2
gas.
2 moles of H+ gives 1 mole of H2.
2H+(aq)+2e−→H2(g)
Pb(NO3 )2 (aq) + 2KI → PbI2 (s) + 2KNO3 (aq)
Zn(s) + H2 SO4 (aq) → ZnSO4 (s) + H2 (g)
At
anode, OH− ion releases two electrons to convert into water and
O2.
2 mole OH− gives 0.5 mole O2, i.e why volume of one gas collected
at
one electron is double of another.
c)
Acid is added to make the water conduct electricity as the distilled
water
is a non-conductor of electricity.
5.
A. Reaction of Magnesium metal:
As,
it is given that the metal ‘M’ on burning gives the dazzling
white
flame and also changes to the white powder ‘N’.
1.
So,
the metal ‘M’ would be Magnesium metal as on the reaction of
burning
in the air, Magnesium reacts with the Oxygen present in
the
air and gives the white powder on burning.
2.
This
Magnesium metal is basically the chemically 3. active one.
Hence, the metal ‘M’ : Magnesium burns in the presence of
Oxygen to form ‘N’ Magnesium oxide.
4.
B.
The balanced chemical equation for the above reaction would be:
C.
Oxidation of Magnesium:
Oxidation
is basically the loss of electrons or the increase in the
oxidation
state of an atom, ion or the molecule.
1.
So
previously when solid Magnesium was present it's oxidation
state
was 0 as the element Magnesium was present with not any
bond.
2.
But,
as soon as it burns in the presence of Oxygen forming the
Magnesium
oxide, it will lose two electrons for getting stable
3.
4.So,
the Oxidation state of Mg in MgO is +2
5.Hence,
Oxidation of Magnesium will take place.
1.
Sodium hydroxide - It is used in the manufacturing of paper.
Chlorine
- It is used to make plastics (PVC), chlorofluorocarbon
(CFC),
chloroform, carbon tetrachloride etc.
Hydrogen
- It is used in the hydrogenation of oils to obtain
vegetable
ghee.
2.
(a) HCl is an acid and NaOH is a base whose combination forms the
common
salt. Its formula is NaCl Sodium chloride. It is obtained
from
seawater.
(b)
Deposits of solid salt which are large crystals and brown due to
impurities
is called rock salt.
(c)
This brown color is due to all the impurities present in the salt
along
with sodium chloride. When the impurities are removed and
pure
sodium chloride is obtained, it turns into white crystals.
3.
When
zinc granules are added to the solution of sulphuric acid
then
zinc
sulfate and hydrogen gas are formed as the product.
The
chemical reaction is as follows:
When
zinc granules are added to the solution of hydrochloric acid
then
zinc chloride and hydrogen gas are formed as the product.
The
chemical reaction is as follows:
4.
When electricity is made to pass through an aqueous solution of
NaCl,
it decomposes to form NaOH. This process is called chloralkali
process
because of two products - chlor for Chlorine and
alkali
for Sodium hydroxide.
(a)
Anode - Cl Gas
(b)
Cathode - H Gas
5.
The Formula actually means that two molecules (or two formula
units)
of CaSO share one molecule of water so that the effective
water
of crystallization for one CaSO unit comes to half a molecule of
water.
5.
Solder is an alloy which is made up of lead and tin.
Solder
has a low melting point so it is used for welding electrical
wires.
4.
Ionic
compounds do not conduct electricity in solid state because
ions
are not free to move. In molten state, ions are free to move.
1.
2.
X is Aluminium.
2Al
+ Fe 0 Al O + 2Fe
3.
Conversion of the carbonate ore into metal oxide: This is done by
calcination
(for carbonate ores). Calcination is the process of
heating
the ore strongly in the absence or limited supply of air. The
zinc
carbonate on heating decomposes to form zinc oxide as shown:
Reduction of the metal oxide to metal :As zinc is moderately
reactive,
zinc oxide cannot be reduced by heating alone. Hence, it is
reduced
to zinc by using a reducing agent such as carbon.
The
purple color of KMnO decolourises and ethanoic acid will be
formed.
The
molecules of covalent compounds are held by weak
intramolecular
forces. Thus, a very small amount of energy is
required
to break the bonds between two or more molecules. That
is
why they have low melting and boiling points.
The
series of organic compounds having the same functional group
and
similar chemical properties is called the homologous series.
Life Process:
(a)
Double circulation is the circulation of blood through the heart
twice
during one complete cycle of the body. It is a type of
circulation
in which the blood passes through two different circuits
of
the body, namely, pulmonary circulation and systemic circulation.
(b)
The separation of the right side and the left side of the heart
is
useful as it allows the oxygenated and deoxygenated blood to
remain
separate, which helps in maintaining the oxygen
concentration
in the body. In mammals and birds, the separation of
the
heart into four chambers helps 3 to increase the efficiency of
oxygen
delivery to the body tissues. The right side of the heart
receives
the deoxygenated blood from the body and pumps it to the
lungs
for oxygenation. The left side of the heart receives the
oxygenated
blood from the lungs and pumps it to the rest of the
body.
This separation ensures that the oxygen-rich and oxygen-poor
blood
do not mix, and the oxygenated blood is delivered efficiently
to
the body tissues
The
anaerobic breakdown of glucose occurs in two different ways.
The
first stage in both processes is the cytoplasmic breakdown of
the
glucose molecule into pyruvate. Fermentation is the term for
the
anaerobic breakdown process in bacteria. Pyruvate is converted
to
carbon dioxide and ethyl alcohol during fermentation. Pyruvate is
converted
to lactic acid in our muscle cells when there is a shortage
of
oxygen. Note: In the two scenarios mentioned above, very little
energy
is emitted.
(a)
Xylem tracheids and xylem vessels are water-conducting tissues
(vascular
tissue) as part of the xylem present in plants. Xylem is
responsible
for the conduction of water from the roots to other
parts
of the plant. Due to transpiration and the resulting pressure
gradient,
water is absorbed into the root xylem of plants. The
transpirational
pull formed causes the roots to absorb water from
the
soil and resulting in the transportation of water.
(b)
Plants have low energy needs as compared to animals due to the
following
reasons:
(i)
Plants are autotrophic organisms, preparing their own food
absorbing
solar energy during the process of photosynthesis.
(ii)
Plants don't move from one place to another like animals so they
consume
less energy.
(iii)
Also, plants possess many dead cells in terms of sclerenchyma
cells
that do not require much energy for maintenance.
The
surface area to volume ratio in unicellular organisms is ideal for
material
exchange or diffusion between the cell and its external
environment,
and this rate of exchange meets the needs of the
unicellular
organism. However, the surface area to volume ratio is
low
in multicellular organisms, and the only way for an organism to
exchange
with the outside world is through its surface, assisted by
a
particular structure or organ, such as the skin. Nevertheless, this
exchange
is insufficient to make up for the millions of cells that
make
up a multicellular organism, each of which has unique needs
depending
on its function.
(1)
Mouth
(2)
Gall bladder
(3)
Pancreas
(4)
Large intestine
(5)
Small intestine.
Control and coordination
1.
Phototropism is the term for a plant's bending towards
light.
The hormone auxins found in plants is to blame. Auxins,
which
are produced at the tips of the shoots of phototropic
plants,
aid in the extension of the cells when the growing
sections
of the plant sense sunlight.
2.
a. Phototropism: It is the direction of growth of a plant in
response
to the direction of the light. Eg - Movement of
shoots
of plants upwards towards light.
b.
Geotropism: It is the term used to describe the directional
movement
of growth that plants display in response to
gravity.
Geotropism is the growth of roots in the direction of gravity.
c.
Chemotropism: The directed movement of growth in response to a
chemical
stimulation is known as chemotropism.
When
the pollen tube expands in the direction of the substance
released
by the ovary during pollen tube germination, this is
known
as chemotropism.
3.
The following are the functions of several brain regions:
The
medulla oblongata is responsible for regulating reflex
responses
and involuntary actions. Moreover, it regulates
vomiting,
salivation, and blood pressure.
Cerebellum:
It directs and synchronizes various muscle
movements.
It is in charge of voluntary movements and keeps
the
body balanced whether one is walking, drinking, catching,
etc.
Parts
of the forebrain include the following:
1.
Cerebrum: Responsible for thinking, speaking, reasoning,
intelligence,
and information utilization.
2.
Olfactory: Lobes in this area are in charge of identifying odors
from
various receptors.
3.
Diencephalon: Regulates body temperature, appetite, thirst,
and
other impulses.
4.
The system that keeps the body's and blood's hormone
balance
stable is known as the hormone feedback mechanism.
That
specific hormone's concentration can either increase or
decrease,
which will either encourage or hinder the hormone's
secretion.
We refer to this as feedback.
There
are two different kinds of feedback. Positive feedback is
referred
to as such, but negative input is not. The hormone is
secreted
or produced more when there is a positive feedback
loop.
On the other hand, the hormone's release is suppressed
by
the negative feedback.
For
instance, eating food high in carbohydrates raises blood
glucose
levels. The pancreas secretes insulin when blood
glucose
levels rise. The cells will be signaled by this insulin to
start
absorbing blood glucose. Therefore The blood's glucose
content
drops. There would be a shortage of glucose in the
circulation
if insulin was still present because more and more
glucose
would be carried inside the cell. In order to stop this,
low
blood glucose levels provide negative feedback, which in
turn
stops the blood's production of insulin.
5.
The medulla controls the involuntary actions whereas the forebrain
is
responsible for controlling the voluntary actions in the body.
1.
2.
They reproduce asexually by the formation of the spores.
The
body of the fungus is composed of hyphae which develop the
sporangium.
The sporangium is a swollen structure at the tip of the
filaments
bearing the spores. The spores are tough and resistant
structures
which are dispersed by the breaking of the sporangium.
3.
Barrier method: Use of condoms.
Surgical
methods: vasectomy (in male), tubectomy (in female).
Intrauterine
devices: copper T.
Oral
contraception: oral hormonal pills.
These
methods help to take care of mother and child. It also helps in
maintaining
a gap between the children so that they can use resources
properly.
4B. Bacterial infections include
chlamydia, gonorrhea, and syphilis. Viral
infections
include human papillomavirus (HPV), herpes (HSV or herpes
simplex
virus), human immunodeficiency virus/acquired immune
deficiency
syndrome (HIV/AIDS) and Hepatitis B.
C.
Contraceptive methods are mainly adopted because of the
following
reasons:
To
prevent unwanted pregnancies.
To
control population rise or birth rate.
To
prevent the transfer of sexually transmitted diseases.
5.
Pollination: Is defined as the deposition of pollen grains on
the
stigma of a flower from anthers belonging to the same
flower,
same plant or a different plant.
Pollination
is of two types
Self
pollination - Stigma receives pollen grains from the same
flower
Cross
pollination - Stigma receives pollen grains from a flower
on
the same plant or a different plant
Wind
and insects are two agents of pollination, called as
Anemophily
and Entomophily respectively.
Example
of wind pollination - Grasses, Gymnosperms, etc.
Example
of insect pollination - Rose, Euphorbia sps, etc.
Pollination
and fertilization - Suitable pollination leads to compatible
pollen
grains being deposited on the stigma, leading to pollen tube
development
and fertilization.
Inherited trait: Inherited
traits are those that are passed down
from
parents to children. An individual's inherited traits are
determined
by their genes.
1.Characters
are passed down from generation to generation.
2.
These characteristics are caused by changes in genes or DNA.
3.
Human inherited traits include hair, skin, eye color, body type,
height,
and susceptibility to certain diseases.
Acquired trait: An
acquired trait is a personality trait that
develops
in a person as a result of environmental influences.
1.
Characters are not passed down from generation to generation
2.
These characteristics emerge in response to their surroundings
or
lifestyle.
3.
These characteristics are not encoded by a living organism's
DNA
and thus cannot be passed down to future generations. The
mouse
will continue to have information for presence of tail in its
DNA.
So, it will- continue to have a tail because absence of tail is an
acquired
trait
Two
pea plants, one with round green seeds (RRyy) and another with
wrinkled
yellow (rrYY) seeds produce F1 progeny that has round,
yellow
(RrYy) seeds. When F1 plants are selfed, the F2 progeny will
have
a new combination of characters, the combination will be
round,
yellow and wrinkled green.
Dominant
traits are always expressed when the connected allele is
dominant,
even if only one copy of the dominant trait exists.
Recessive
traits are expressed only if both the connected alleles
are
recessive. If one of the alleles is dominant, then the associated
characteristic
is less likely to manifest.
(a)
Dominant trait is tallness which is represented by TT and
recessive
trait is dwarfness which is represented by it . Thus, on
crossing
the dominant trait with dwarf trait , Tt will be obtained
Hence
, Tt will be the set of genes present in the F1 Generation .
(b) According to Mendel's law of monohybrid
inheritance and law of
segregation
, if a single pair of contrasting characteristics were
cross-bred
by self-pollination , then , in F1 progeny , plants with
dominant
traits are produced . Thus only tall plants are observed in
the
F1 Progeny because T are called dominant traits and they
express
themselves.
In
asexual reproduction, DNA is copied as it is from one generation
to
another, there is no mating or mixing of genes. Asexual
reproduction
results in offspring with identical genetic information.
There
is very little genetic variation between parent and offspring
It
takes large amount of time for different trait to develop in case
of
asexual reproduction Hence, if a trait exist in 70% of population,
it
would have arisen earlier as it would have been replicated over
more
number of generations.
5.Laws of reflection of 1. light states that:
(i)
The angle of incidence is equal to the angle of reflection.
(ii)
The incident ray, the reflected ray and the normal to the mirror
at
the point of incidence all lie in the same plane.
2.
Refractive index (RI) if glass is 1.5
Refractive
index (RI) of water is 1.33
Now,
RI of glass with respect to water = RI of glass/RI of water
=
1.5/1.33 = 1.127
RI
of water with respect to glass = RI of water/RI of glass
=
1.33/1.5 = 0.89
Since
velocity of light in medium is inversely proportional to its
refractive
index, the light will travel faster in optically rarer
medium
i.e. water.
3.
Here, u = 30, v = -60
As
1/f = 1/u + 1/v = 1/(-60) + 1/(-30) = -1/20
f
= 20, The mirror is concave.
As
the image is formed on the screen, it is real and inverted.
From
h2/h1 = -v/u = +60/-30 = -2
h2
= -2xh1 = -2 x 2.4 = -4.8 cm
This
is the size of inverted image.
4.
(i) A ray of light incident on a concave lens is parallel to its
principal
axis, the diagram can be drawn as follows:
4.
The refracted ray appears to pass through focus on the same side
of
the lens.
(ii)
If a ray of light incident on a concave lens is passing through its
optical
centre then the refracted ray will go without deviation.
(iii)
If a ray of light incident on a concave lens is directed towards
its
principal axis then it will go parallel to principal axis.
5.
Object distance, u = -60 cm
Focal
length of the lens, f = -30 cm
Step
2: Finding the image distance using the lens formula:
Using
the lens formula, we get
1/f
= 1/v -1/u
1/v
= 1/f + 1/u
1/v
= 1/(-30) + 11/(-60)
1/v
= 1/-20
v
= -20cm
Thus,
the distance of the image from the lens is 20 cm.
(ii)
The four characteristics of the image formed by the lens in this
case
are:
The
image formed is virtual as the given lens 1. is a concave lens.
2.The
image is erect as it formed above the principal axis.
3.
Image is diminished (smaller than the object).
4.
Image is formed at a distance of 20 cm from the optical centre of
the
concave lens on the same side of the object.
1.
Splitting of white light into its seven constituent colors due to
refraction
is known as dispersion of white light.
Cause
of dispersion: When a beam of white light enters a prism, it gets
refracted
and splits into seven constituent colors. The splitting of the
light
ray occurs due to the different bending angle for each color.
Thus,
each color ray when passing through the prism bends at
different
angles with respect to the incident beam, thus giving rise to
a
spectrum.
2.
Newton was the first to use a glass prism to obtain the spectrum of
a
white light. He then placed a second identical prism in an inverted
position
with respect to the first prism. This allowed all the colors of
the
white light to pass through the second prism combining to form a
white
light emerging from the other side of the second prism. This
made
him believe that white light was composed of different colors.
Human eye & colorful world
4.
(i) Cornea: It is a transparent bulge on the front surface of eyeball
which
refracts most of the light rays entering the eye.
(ii)
Iris : A thin, pigmented structure found in the eye that can
regulate
the amount of light that can enter the retina.
(iii)
Pupil: Black hole in the centre of the iris of the eye which permits
light
towards retina.
5.
The student is suffering from myopia.
The
two possible reasons due to which the defect of vision arises are:
excessive
curvature of the eye lens and elongation of the eye ball.
A
student with myopia has the far point nearer than infinity, thus, the
image
of a distant object is formed in front of the retina.
Correction of myopia: This
defect can be corrected by using a
concave
lens of suitable power as it brings the image back on to the
retina,
thus the defect is corrected.
1.
The total potential difference across a combination of resistors in
series
is equal to the sum of a potential difference across the
individual
resistors. V=V1+V2+V3
Let
I be the current in the circuit. The current through each resistor
is
also I. It is possible to replace the three resistors joined in series
by
an equivalent resistor of resistance R.
Applying
Ohm's law, V=IR
V1=
IR1
V2=
IR2
V3=
IR3
V=V1+V2
+ V3
IR=
IR1+ IR2 + IR3
R=R1+
R2+R3
Two
parallel combinations must be connected in series with each other
to
get the effective resistance of 8Ω. The effective resistance of
each
of the parallel combination is 4Ω resistors are added together
to
get 8Ω effective resistance.
2.
It states that the potential difference V, across the ends of a
given
metallic wire in an electric circuit is directly proportional to the
current
flowing through it, provided its temperature remains the
same.
Mathematically,
V ∝ I
V
= RI
where
R is resistance of the conductor.
or
R = V/I
So
the slope of V-I graph at any point represents
the
resistance of the given conductor.
Electricity
3.
Kilowatt (kW) - a large unit of electric power Kilowatt hour (kWh) -
a
commercial unit of energy.
1
kWh = -3.6 x 10^6 Joules.
Potential
difference = 5V, Current = 500 mA = 500 x 10^(-3) A
P
= VI
=
5V x 500 x 10^(-3) = 2.5W
R
= V/I
=
5/500 x 10^(-3) x 10Ω
=
100Ω
4.
Since both the bulbs are connected in parallel and to a 220 V
supply,
the voltage across each bulb is 220 V. Then
Current
drawn by 100 W bulb,
I1
= power/voltage = 100W/220V = 0.454A
Current
drawn by 60 W bulb,
I2
= 60W/220V = 0.273 A
Total
current drawn from the supply line,
I
= I1 + I2 = 0.454 A + 0.273 A = 0.727 A = 0.73 A
5.
(a) Given, voltage = 2V + 2V + 2V = 6V
Current
through 10Ω resistance,
I(10)
= V/R=6/10 = 0.6 A
Current
through 20Ω resistance,
I(20)
= V/R =6/20 = 0.3 A
Current
through 30Ω resistance,
I(30)
= V/R=6/30 = 0.2 A
(b)
Total current in the circuit, I = I(10) + I(20) + I(30)
=
0.6+0.3 +0.2 = 1.1 A
(c)
Total resistance of the circuit,
1/Rp=1/10+1/20+1/30=11/60
1.
(i) No, alpha particle will not experience any force if it is at rest,
because
only moving charge particle can experience force when placed
in
a magnetic field.
(ii)
No, alpha particle will not experience any force if it moves in the
magnetic
field parallel to field lines because charge particle
experiences
force only when it moves at an angle other than 0° with
magnetic
field.
(iii)
Alpha particle will experience a force in the direction
perpendicular
to the direction of magnetic field and direction of
motion
of alpha particle.
2.
Many electric appliances of daily use like electric press, heater,
toaster,
refrigerator, table fan etc. have a metallic body. If the
insulation
of any of these appliances melts and makes contact with the
metallic
casing, the person touching it is likely to receive a severe
electric
shock. This is due to the reason that the metallic casing will
be
at the same potential as the applied one. Obviously, the electric
current
will flow through the body of the person who touches the
appliance.
To avoid such serious accidents, the metal casing of the
electric
appliance is earthed. Since the earth does not offer any
resistance,
the current flows to the earth through the earth wire
instead
of flowing through the body of the person.
3.Fleming’s
left hand rule: Stretch the forefinger, middle finger and
the
thumb of your left hand mutually perpendicular to each
other.
If the forefinger indicates the direction of magnetic field
and
the middle finger indicates the direction of current, then the
thumb
will indicate the direction of motion of conductor
Magnetic effects of current
4.
Imaginary continuous closed curves used to represent the
magnetic
field in a region is known as magnetic field lines. It is
directed
from north pole to south pole outside the magnet and
south
pole to north pole inside the magnet.
(a)
The direction of magnetic field (B) at any point is obtained by
drawing
a tangent to the magnetic field line at that point. In case, two
magnetic
field lines intersect each other at the point P as shown in
figure,
magnetic field at P will have two directions, shown by two
arrows,
one drawn to each magnetic field line at P, which is not
possible.
(b)
It is taken by convention that the field lines emerges from
north
pole and merge at the south pole. Inside the magnet, the
direction
of field lines is from its south pole to its north pole.
Thus,
the magnetic field lines are closed curves.
5.
Solenoid: A coil of many circular turns of insulated copper
wire
wrapped in the shape of cylinder is called solenoid.
(ii) Magnetic field lines around a bar magnet.
Following
are the distinguishing features between the two fields.
(a)
A bar magnet is a permanent magnet whereas solenoid is
an
electromagnet, therefore field produced by solenoid is
temporary
and stay till current flows through it.
(b)
Magnetic field produced by solenoid is more stronger than
magnetic
field of a bar magnet.
1.
When UV rays interact with oxygen molecules, they release
a
free oxygen atom, which then joins with another oxygen
molecule
to generate ozone. O + O2 → O3 (Ozone) Because
ozone
absorbs and shields us from the Sun's harmful UV rays,
its
decrease is a reason for concern.
2.
Ponds and lakes being natural ecosystems have natural
decomposers
and cleaners embedded as an integral part of the
ecosystem,
hence we do not have to clean them. Aquariums
are
artificially built ecosystems which generally do not contain
every
aspect of a natural ecosystem.
3.
Because they rely only on simple inorganic compounds like carbon
and
water to manufacture their own food, green plants are considered
producers
because they not only sustain all other species but also
produce
their own food.
4.
By encouraging the use of recycled materials and reducing the
use
of throwaway things, we can lessen the issue of garbage disposal.
Separating
garbage that is biodegradable from that that is not
before
disposing of it.
Recycling
the garbage that isn't biodegradable.
Our Environment
5.
Ecosystem can be defined as a system composed of biotic
and
abiotic components and the interactions between them
The
energy flow in an ecosystem is always from producers to
consumers
moving in the upward direction, that is from
