(i) Tidal energy does not produce any pollution.
(ii) It does not use any fuel and does not produce any waste.
(iii) Tides are predictable, so tidal energy can be produced at any time.
(iv) water is denser than air and therefore can generate electricity at lower speeds than wind turbines.

Behavioural Changes:
Adverse effects among adolescents are:
(i) Drop in academic performance, absence from school or college.
(ii) Lack of interest in personal hygiene, isolation, depression, fatigue and aggressive behaviour.
(iii) Deteriorating relationship with family and friends.
(iv) Change in food and sleeping habits.
(v) Fluctuation in body weight and appetite.

The device which helps in explaining the concepts easily through pictures is known as 'Visual Communication Device: For example photos, audio-visuals, drawings, animations all these can be created easily with the help of computer. Cinema is a good example for 'Visual Communication Device'.

Ethanoic acid is used
(i) as a laboratory reagent.
(ii) for coagulating rubber from latex.
(iii) in the preparation of dyes, perfumes and medicines.

Extraterrestrial or Cosmic orgin: Some scientists still believe that life came from outer space. This states that units of life called spores (Panspermia) were transferred to different planets including Earth. This is still an idea of some Astronomers.

Neurotransmitters are the chemicals which allow the transmission of nerve impulse from the axon terminal of one neuron to the dendron of another neuron or to an effector organ. eg. Acetylholine.

(i) In a chemical reaction, the atoms of the reacting molecules or elements are rearranged to form new molecules
(ii) Old chemical bonds between atoms are broken and new chemical bonds are formed.
(iii) Bond breaking absorbs energy where as bond formation releases energy

The process in which two lighter nuclei combine to form a heavier nucleus is termed as "nuclear fusion".
Eg: ₁H² + ₁H²- ₂He⁴ + Q (Energy)
Here, ₁H² represents an isotope of hydrogen known as "deuterium". The average energy released in each fusion reaction is about 3.84 x 10^-12J.

If a liquid is heated directly without using any container, then the expansion that we observe is termed as "real expansion" of the liquid.

Sodium

(i) Equivalent resistance of series combination of resistors is more than the equivalent resistance of the parallel combination of resistors.
So, the resistance of circuit I is more than the resistance of circuit II.
(ii) Since, current \(\alpha \frac{1}{resistance}\)
∴ So current in circuit II is more than the current in circuit I.
(iii) Potential difference across each resistor is equal in circuit II.

(i) It stimulates the ovary to develop into fruit.
(ii) It helps in development of new characters from two different individuals

(i) Components of blood: The blood consists of two main components. The fluid plasma and the formed elements (blood cells) which are found suspended in the plasma.
(ii) Blood cells are classified into erythrocytes, leucocytes and platelets.

(i) According to Aristotle, A moving object naturally comes to rest without any external influence or force. Such motions are termed as "natural motion".
(ii) Natural motion is an unforced motion. According to Newtonian mechanics, the natural motion is a uniform rectilinear motion, following its first law of motion. In general relatively, a natural motion may be linear or curved.

(i) The female reproductive system of rabbit consists of a pair of ovaries which are small ovoid structures. They are located behind the kidneys in the abdominal cavity.
(ii) A pair of oviducts opens into the body cavity by a funnel shaped opening from each side of the ovary.
(iii) The anterior part of the oviduct is the fallopian tube. It leads into a wider tube called the uterus.
(iv) The uterus join together to form a median tube called vagina.
(v) The common tube is formed by the union of urinary bladder and the vagina and is called the urinogenital canal or vestibule. It runs backwards and opens to the exterior by a slit-like aperture called vulva.
(vi) A pair of Cowper's gland and perineal gland are the accessory glands present in the female reproductive system

(i) In anaerobic respiration the amount of energy produced is very less.
(ii) Aerobic respiration is seen is humans wherein the number of ATP molecules produced from a glucose molecule is more than an aerobic respiration.

Biogas is the mixture of methane (nearly 75 %), hydrogen sulphide, carbon dioxide and hydrogen. It is produced by the decomposition of animal wastes (cow dung) and plant wastes in the absence of oxygen. It is also commonly called as 'Gobar gas' since the starting material used is cow dung called as gobar.
Uses of biogas:
(i) It is used as fuel for cooking.
(ii) It is used to run motors and pump sets.
(iii) It is used to generate electricity.
Advantages of biogas:
(i) It burns without smoke and therefore causes less pollution.
(ii) An excellent way to get rid of organic wastes like bio-waste and sewage material.
(iii) Left over slurry is good manure rich in nitrogen and phosphorus
(iv) It is safe and convenient to use.
(v) It can reduce the amount of greenhouse gases emitted.

The following steps may help in controlling and prevent the spreading of HIV infection:
(i) Screening of blood from blood banks for HIV before transfusion.
(ii) Ensuring the use of disposable needles and syringes in hospitals and clinics.
(iii) Advocating safe sex and advantages of using condoms.
(iv) Creating awareness campaign and educating people on the consequences of  AIDS.
(v) Persons with HIV/AIDS should not be isolated from the family and society.

Genetically Modified Organisms:
(i) Genetic modification refers to the alteration or manipulation of genes in the organisms using rDNA techniques in order to produce the desired characteristics.
(ii) The DNA fragment inserted is called transgene. Plants or animals expressing a modified endogenous gene or a foreign gene are also known as transgenic organisms.
Advantages:
(i) The transgenic plants are much stable, with improved nutritional quality, resistant to diseases and tolerant to various environment conditions.
(ii) Similarly transgenic animals are used to produce proteins of medicinal importance at low cost and improve livestock quality. eg Golden Rice is a genetically modified Rice which can produce Beta carotene.

(i) Pictures and Audio-Visuals give us more understanding than teaching and writing on black board. So, any visual representation of the concepts would help us to understand better and make teaching simple
(ii) Yes. Visual Communication helps us to easily conceptualize complicated theorems and concepts. When the teacher shows pictures / videos that represent the concept, we would easily relate to its application and firmly understand the concept without any mis-perception
(iii) Pictures, Audio-Visuals, animations provide additional information and helps us to easily correlate the concepts. We could easily remember the visuals than black board writing, and visualize it, so that we do not forget and we could easily recollect at the time of examination.

Detergents are better than soaps because they,
(i) can be used in both hard and soft water and can clean more effectively in hard water than soap.
(ii) can also be used in saline and acidic water.
(iii) do not leave any soap scum on the tub or clothes.
(iv) dissolve freely even in cool water and rinse freely in hard water.
(v) can be used for washing woollen garments, where as soap cannot be used.
(vi) have a linear hydrocarbon chain, which is biodegradable.
(vii) are active emulsifiers of motor grease.
(viii) do an effective and safe cleansing, keeping even synthetic fabrics brighter and whiter.

When the thyroid gland fails to secrete the normal level of hormones, the condition is called thyroid dysfunction. It leads to the following conditions.
Hypothyroidism: It is caused due to the decreased secretion of the thyroid hormones. The abnormal conditions are simple goitre, cretinism and myxoedema.
Goitre:
(i) It is caused due to the inadequate supply of iodine in our diet.
(ii) This is commonly prevalent in Himalayan regions due to low level of iodine content in the soil.
(iii) It leads to the enlargement of thyroid gland which protrudes as a marked swelling in the neck and is called as goitre.
Cretinism:
(i) It is caused due to decreased secretion of the thyroid hormones in children.
(ii) The conditions are stunted growth, mental defect, lack of skeletal development and deformed bones. They are called as cretins
 Myxoedema:
(i) It is caused by deficiency of thyroid hormones in adults.
(ii) They are mentally sluggish, increase in body weight, puffiness of the face and hand, oedematous appearance.
Hyperthyroidism:
(i) It is caused due to the excess secretion of the thyroid hormones which leads to Grave's disease (Exopthalmic goitre).
(ii) The symptoms are protrusion of the eyeballs (Exopthalmia), increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.

(i) Arachaeopteryx.
(ii) It had wings with feathers like a bird.
(iii) It had conical teeth like a reptile.

Reversible Reactions: A reversible reaction is a reaction that can be reversed, i.e., the products can be converted back to the reactants. A reversible reaction is represented by a double arrow with their heads in the direction opposite to each other. Thus, a reversible reaction can be kept

Explanation: The compound 'AB' undergoes decomposition to form the products 'A' and 'B'. It is the forward reaction. As soon as the products are formed, they combine together to form 'AB': It is the backward reaction
PCl₅(g) ⇌ PCl₃(g) + CI₂(g)
Irreversible Reactions: The reaction that cannot be reversed is called irreversible reaction. Consider the combustion of coal into carbon dioxide and water.
C_(s) + O_2(g) ⟶ CO_2(g)+ Heat
Coal oxygen Carbon dioxide
In this reaction, solid coal burns with oxygen and gets converted into carbon dioxide gas and water. As the product is a gas, as soon as it is formed it escapes out of the reaction container. It is hard to decompose a gas into a solid. Thus, the backward reaction is not possible in this case. So, it is an irreversible reaction

Linear expansion:
(i) When a body is heated or cooled, the length of the body changes due to change in its temperature. This expansion is said to be a linear or longitudinal expansion.
(ii) The ration of increase in length of a body per degree celsius rise in temperature to its unit length is called the coefficient of linear expansion. Its SI unit is per Kelvin. The value of coefficient of linear expansion is different for different materials.

(iii) The equation relating the change in length to the change in temperature of a body is given below:
\(\frac { \triangle L }{ { L }_{ 0 } } \) =α_L ΔT
ΔL  - Change in length
L₀ - Original length
ΔT - Change in temperature
α_L - Coefficient of linear expansion.

(i) First law of refraction : The incident ray of light, the refracted ray of light and the normal to the refracting surface all lie in the same plane.
(ii) Second law of refraction : The ratio of the sine of the angle of incidence and sine of the angle of refraction is equal to the ratio of refractive indices of the two media. This law is also known as Snell's law.
\(\frac{\operatorname{sin i}}{\sin x}=\frac{\mu_2}{\mu_1} .\).

(i) The listener moves towards or away from a stationary source.
(ii) The source moves towards or away from a stationary listener.
(iii) Both source and listener move towards or away from each other.
(iv) The medium moves when both source and listener are at rest

Man is omnivorous in his food habit. He eats plant and animal food. Therefore he has well CI developed incisors and canines. Rabbits are herbivorous in mode of nutrition. They need sharp incisors only. Canines or tearing teeth are hence absent in rabbits.

Magnetic separation method:
(i) Principle: Magnetic properties of the ores form the basis of separation. When either the ore or the gangue is magnetic, this method is employed. E.g. Tin stone SnO₂ The ore of tin.
(ii) Method: The crushed ore is placed over a conveyer belt which rotates around two metal wheels, one of which is magnetic. The magnetic particles are attracted to the magnetic wheel and fall separately apart from the non-magnetic particles.

Based on the position of centromere, the chromosomes are classified as Telocentric, Acrocentric, Submetacentric andMetacentric.
(i) Telocentric - The centromere is found on the proximal end. They are rod shaped chromosomes.
(ii) Acrocentric - The centromere is found at the one end with a short arm and long arm. They are also rod - shaped chromosomes.
(iii) Submetacentric - The centromere is found near the centre of the chromosome. Thus forming two unequal arms. They are J

(iv) Metacentric - The centromere occurs in the centre of the chromosome and form two equal arms. They are V shaped chromosomes.

Cross pollination takes place through the agency of animals, insects, wind and water.
Pollination by wind (Anemophily):
(i) The pollination with the help of wind is called anemophily.
(ii) The anemophilous flowers produce enormous amount of pollen grains.
(iii) The pollen grains are small, smooth, dry and light in weight.
(iv) The stigmas are comparatively large, protruding and sometimes hairy, to trap the pollen grains. E.g: Grasses and some cacti.
Pollination by insects (Entomophily):
(i) Pollination with the help of insects like honey bees, flies are called entomophily.
(ii) To attract insects these flowers are brightly coloured, have smell and nectar
(iii) The pollen grains are larger in size, the exine is pitted, spiny etc., so they can be adhered firmly on the sticky stigma. Approximately, 80% of the pollination done by the insects is carried by honey bees. 
Pollination by Water: The pollination with the help of water is called hydrophily. This takes place in aquatic plants.
(i) Pollen grains are produced in large numbers.
(ii) Pollen grains float on surface of water till they land on the stigma of female flowers. E.g:Hydrilla, Vallisneria. Pollination by Animals :
(i) When pollination takes place with the help of animals, it is called Zoophily.
(ii) Flowers of such plants attract animals by their bright color, size, scent etc. E.g: Sun bird pollinates flowers of Canna, Gladioli etc., Squirrels pollinate flowers of silk cotton tree.

(i) Let M be the mass of the Earth and m be the mass of the object.
(ii) The entire mass of the earth is assumed to be concentrated at its centre. The radius of the earth is R (= 6378 km = 6400 km approximately).
(iii) By Newton's law of gravitation, the force acting on the object is given by
F = G M m / R²  ............. (A)
(iv) According to Newton's second law, the force acting on the object is given by the product of its mass and acceleration. Here acceleration of the is under action of gravity hence a =g.
F=ma =mg
F = weight = mg
Comparing equations (A) and (B), we get
g= GM/ R²
Acceleration due to gravity
g=\(\frac { GM }{ { R }^{ 2 } } \).

The atomicity of an element can be derived using Avogadro's hypothesis. Let us consider the following equation

According to Avogadro's law, 1 volume of any gas occupy 'n' number of molecules.

if n = 1 then

(i) 1 molecule of hydrogen chloride gas is made up of \(\frac{1}{2}\) molecule of hydrogen and \(\frac{1}{2}\) molecule of chlorine
(ii) But 1 molecule of hydrogen chloride contains one atom of hydrogen and I atom of chlorine
(iii) Hence \(\frac{1}{2}\) molecule of hydrogen = 1 atom of hydrogen
(iv) Or 1 molecule of hydrogen = 2 atoms of hydrogen
(v) So the atomicity of hydrogen is 2, and molecular formula is H₂
Similarly,
\(\frac{1}{2}\) molecule of chlorine = 1 atom of chlorine 1molecule of chlorine = 2 atoms of chlorine So the atomicity of chlorine is 2, and its molecular formula is Cl₂

₆C¹⁴-￫ _-1e⁰+ ₇N¹⁴

Initial temperature, t₁ = 0°C
Final temperature, t₂ = 25°C
Coefficient of linear expansion of metal,
α₁ =18 x 10^-6 C^-1
Measured length, l₁ = 50 cm
To find: True (or) Actual length l₂ = ?
\(\frac { \triangle l }{ l\triangle T } =\frac { ({ l }_{ 2 }-{ l }_{ 1 }) }{ { l }_{ 1 }(t_{ 2 }-{ t }_{ 1 }) } \)
l₂ = I₁ (1 + α (t₂ - t₁)
∴ l₂ = 50 x (1 + 18 x 10 ^-6 x (25 - 0)
= 50 x (1 + 450 x 10^-6)
= 50 x (1 + 0.00045)
∴ l₂ = 50.225 cm
The true length of the object at 0⁰C =50.225 cm.

Focal length, f = - 20 cm (concave lens)
h₀ = 5 cm
Height of the object, h₀ = 5 cm
Image distance v = -15 cm
\(\frac { 1 }{ f } =\frac { 1 }{ v } -\frac { 1 }{ u } \quad \frac { 1 }{ v } -\frac { 1 }{ f } \)
=\(\frac { 1 }{ u } \)
\(\frac { 1 }{ u } =\frac { 1 }{ -15 } +\frac { 1 }{ (20) } \)
=\(\frac { -20+15 }{ 300 } =\frac { -5 }{ 300 } \)
u = -60 cm
Magnification, m = \(\frac { { h }_{ i } }{ { h }_{ 0 } } =\frac { v }{ u } \)
h_i = \(\frac { v }{ u } \).h₀
Size of the image, h_i =\(\frac { -15 }{ -60 } \) x 5
= \(\frac { 5 }{ 4 } \) = 12.5 cm
Image is diminished & Virtual

Given 
Frequency g car's distance, n = 800 Hz
Velocity of source, Vs = 120ms^-1
Velocity of sound, v = 340 ms^-1
To find: Frequency emitted by the car, n' = ?
Solution
Apparent frequency, n' =\(\left( \frac { v }{ v-{ v }_{ s } } \right) \times n\)
\(=\frac { 340 }{ 340-120 } \times 800\)
\(=\frac { 340 }{ 220 } \times 80\)
Apparent frequency, n' = 1236 Hz

Given :
Charge passing through bulb, q = 30C
Current drawn by 100 W bulb, I = 680 x 10^-3 A
To find: Time taken to pass
through the bulb t =? t=\(\frac{q}{I}\)
Solution :
\(I=\frac { q }{ t } =\frac { 30 }{ 680\times { 10 }^{ -3 } } \)
=441.173
Time required, t =7.35 min

Given:
Mass of the bullet, m = 20 x 10^-3 kg
Initial velocity, u = 300 m/s
Final velocity, v = 0
Distance, s = 2 cm = 2 x 10^-2m
To find: Force exerted by the bullet, f = ?
Using equations of motion,
v² = u² + 2 as
0 = (300)² + 2(a) x 2 x 10^-2
a=\(\frac { (300)^{ 2 } }{ 4\times 10^{ -2 } } =\frac { 9\times 10^{ 4 } }{ 4\times { 10 }^{ -2 } } \)
a = -2.25 x 10⁶ m/s²
a = 2.25 x 10⁶ m/s²
Average force,
F = ma
= 20 x 10^-3 x 2.25 X 10⁶
F = 45 x 10^-3 = 4.5 x 10⁴ N

Gram molecular of CO₂ = 44g
Number of molecules present in 44g of CO₂
= 6.023 X 10²³
∴ Number of molecules present in 11g of CO₂
= \(\frac{6.023\times{10}^{23}}{44}\)x 11
= 1.53 x 10²³ molecules.

Rani did not wear a helmet. Some people wear a helmet but don't fasten the strap. When they fall down from the bike, the helmet falls off and they are injured. Thus a helmet worn properly can save lives.

The speed of the sound, \(v\alpha \sqrt { \frac { I }{ d } } \)
The value of \(\frac { I }{ d } \) is much higher for solids. So sound travels faster in solids then gases.