Carbon atoms have 4 electrons in their outcomes shell. So need to gain or lose electrons to attain noble gas configuration.
(i) It could gain four electrons forming c^4- anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons.
(ii) It could lose four electrons forming C⁴⁺ cations. But it would require a large amount energy to remove four electrons from its outermost shell.
Because of these reasons, carbon shares its valence electrons to complete its octet with other atoms to form covalent bonds.
(a) Covalent compounds are bad conductors of electricity because they do not contain ions.
(b) Covalent compounds have usually low melting and boiling because they are made up of electronically neutral molecule. So the force of attraction between the molecules of a covalent compound is very weak. Only a small amount of heat energy is required to break these weak molecular forces, due to which covalent compounds have low melting and boiling points.

Nutrition can be defined as the process of acquiring source of energy from the outside to the inside of the body. Nutrients are the different sources of energy acquired by living organisms by the process of nutrition.

Activity:
To show the effect of magnetic field on current -carrying conductor

Materials Required:
A small aluminium rod, a horse-shoe magnet, battery, plug key, wires and a stand.

Procedure:
The aluminium rod is suspended horizontally from the stand and tied to two wires at its ends. The wires are attached to rheostat, battery and a plug key to make the circuit.

The horse-shoe magnet is positioned in a way that the aluminium rod lies between the two poles of the magnet. If the South Pole is above the aluminium rod and the North Pole is below it. The plug key is inserted to initiate current supply to the rod.

It is observed that the aluminium rod deflects towards left.
When the direction of the current is reversed the aluminium rod deflects towards right.

Conclusion:
When a current carrying conductor is placed within a magnetic field, the conductor experiences deflection. Fleming's Left Hand Rule explains the direction of displacement in this case. Let us assume that the current is moving in anti-clockwise direction in the loop. In that case, the magnetic field would be in clockwise direction; at the top of the loop. Moreover, it would be in anticlockwise direction at the bottom of the loop.

Since the metal X react with cold water, it must be high in the reactivity series i.e., sodium or potassium.
X is alkali metal, Na or K.
Since the metal Y reacts with hot water, it must be middle in the reactivity series i.e., magnesium or calcium.
Y is alkaline earth metal, Mg or Ca.
Since the metal X reacts with steam only, it must be low in the reactivity series i.e., iron Z is Fe.
Increasing reactivity series : Na > Mg > Fe.

A number of resistors are said to be connected in series, if these are joined end to end and the same, current flows through each one of them when a potential difference is applied across the combination. If we connect ammeter first between the point A and R₁, then between R1 and R₂:R₂ and R₃ and lastly between R₃ and the point B; it is same as current.

(a) General metabolism.
(b) Controls blood sugar level.
(c) Prepare the body for 'fight or flight' response.
(d) Promotes growth and development.
(e) Triggers sperm production and is responsible for the development of secondary sexual characters in males.

The Substance which is used for making different shapes is Plaster of Paris.  Its chemical name is calcium sulphate hemihydrate \([CaSO_4.1/2H_2O].\) The two formula unit of \(CaSO_4\) share one molecule of water.  As a result, it is soft.  When it is left open for some time, it absorbs moisture from the atmosphere and forms gypsum, which is a hard solid mass.

\(\underset{Plaster\ of\ Paris}{​​CaSO_4.{1\over 2}H_2O}+1{1\over2}{H_2O}\rightarrow \underset{Gypsum}{CaSO_4.2H_2O}\)

(a) Zinc sulphate and copper is formed when zinc reacts with copper sulphate,
\(\underset{Zinc}{Zn( s)} + \underset{Copper\ sulphate}{CuSO_4} (aq) \rightarrow \underset{Zinc\ sulphate}{ZnSO_4(aq)} + \underset{Copper}{Cu}\)
(b) Hydrochloric acid forms aluminium chloride and hydrogen gas when reacts with aluminium metal.
\(2AI + 6HCI\rightarrow 2AlCl_3 + 3H_2\)
(c) When silver metal is added to copper sulphate solution, no reaction takes place because silver is less reactive than copper

A. Silver nitrate
B. Copper
C. Copper nitrate
Displacement reaction

Electrolysis
X = water, Y = hydrogen, Z = oxygen

Butanol

ZnO(s) and CO₂(g) are formed.
Chemical Equation:
ZnCO₃ → ZnO + CO₂

The two metals are:
(i) Calcium (Ca)
(ii) Magnesium (Mg)
They start floating because the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal.

Silver or Copper.

Reaction of an acid with a metal:
When an acid reacts with a metal, it forms a salt.
Hydrogen which is in all the acids gets displaced and liberated as hydrogen gas.
Acids + Metals \(\rightarrow\) Salt + Hydrogen gas

As the wire is bent in the form of a closed circle, it will be have like two resistors of 5\(\Omega \) each, connected in parallel. Therefore, the equivalent resistance can be calculated as:
\(\frac { 1 }{ R_{ eq } } =\frac { 1 }{ { R }_{ 1 } } +\frac { 1 }{ { R }_{ 2 } } \)
\(\frac { 1 }{ R_{ eq } } =\frac { 1 }{ 5 } +\frac { 1 }{ 5 } \)=\(\frac { 1 }{ R_{ eq } } =\frac { 2 }{ 5 } \)
\(\frac { 1 }{ R_{ eq } } =\frac { 5 }{ 2 } =2.5\Omega \)
The effective resistance between the two points at the ends of an diameter of the circle is 2.5 \(\Omega \).

Atomic mass as a physical property and nature and formulae of oxide and hydride formed, and chemical property was used by Mendeleev.
Observations :
(i) Increasing order of atomic weights could not be maintained while matching chemical properties. Chemical properties do not depend atomic mass.
(ii) Isotopes have different atomic mass but same chemical properties.

(i) (-Cl) Halogen (Chloro)
(ii) -OH) Alcohol

Direction of induced current is given by Fleming's right hand rule according to this rule, stretch the thumb, fore-finger and the middle finger of the right hand such that they are mutually perpendicular.
If the fore-finger points in the direction of magnetic field the thumb shows the direction of motion and middle finger points in the direction of induced current.

It should be connected with live wire.

It is a vector quantity as it has both magnitude and direction.

Oxides ores, carbonate and sulphide ore.

As soon as a piece of sodium metal is dropped into water, bubbles will come out showing the evolution of a gas is hydrogen. The reaction that takes place between sodium metal and cold water is given below :
2Na        +   2H₂O       →  2NaOH          +  H₂
Sodium    Water(cold) Sodium hydroxide Hydrogen

Breathing is the process of taking in oxygen (inhalation) and giving out carbon dioxide (exhalation)

The transport of food from the leaves to the different parts of the plant is called translocation.

Respiration involves the breaking down of digested food using oxygen.As respiration produces a lot of energy in the form of ATP, this process is exothermic in nature.

The receptors present in our eyes are called photoreceptors, as they are light sensitive.

Brain and spinal cord.

The receptors present in our nose and helps in detecting smell are called olfactory receptors.

Watt

It means that 1 joule of work will be done in order to move 1 coulomb of charge from point A to B.

B will be basic nature, with pH = 8.

A solution of ammonia in water results in the formation of ammonium hydroxide (NH₄OH).  Ammonium hydroxide is basic in nature and turns red litmus blue.

Example of a decomposition reaction:
\(\underset { limestone }{ { CaCO }_{ 3 }(s) } \overset { heat }{ \rightarrow } \underset { quick\quad lime }{ CaO(s) } +C{ O }_{ 2 }(g)\)
Here, when limestone (calcium carbonate) is heated, it decomposes into quick lime (calcium oxide) and carbon di oxide (gas).

(i) Change in colour: Reaction between lead nitrate solution and potassium iodide solution.
Pb(NO₃)₂(aq) + 2KI \(\longrightarrow \) PbI₂(s) + 2KNO₃(aq)
In this reaction, colour changes from colourless to yellow.
(ii) Change in temperature: Action of dilute sulphuric acid on zinc.
Zn(s) + H₂SO₄(aq) \(\longrightarrow \) ZnSO₄(aq) + H₂
In this reaction, heat is evolved
(iii) Formation of precipitate : Action of barium chloride on sodium sulphate.
BaCl₂(aq)+ Na₂SO₄(aq) \(\longrightarrow \) BaSO₄(s) + 2NaCl(aq)

(i) Na₂CO₃(s) + 2HCl(aq) \(\longrightarrow \) 2NaCI(aq) + H₂O(I) + CO₂(g)
(ii) CaO(s) + H₂O(I) \(\longrightarrow \)Ca(OH)₂(aq) + Heat
(iii) Pb(NO₃)₂(aq) + NaCl(aq) \(\longrightarrow \) PbCI₂(s) + 2NaNO₃(aq)

The reaction between an acid and a base that gives a salt and water is known as a neutralisation reaction.
Base + Acid ➝ Salt + Water
NaOH(aq) + HCI(aq) ➝ NaCl(aq) + H₂O(I)

When baking soda is heated, it decomposes to produce sodium carbonate, water and CO₂ gas.
\(2NaHCO_3 \xrightarrow{\Delta} Na_2CO_3 + H_2O+ CO_2\)
CO₂ gas produced during the reaction makes the cake or bread spongy and fluffy.

Different metals react with oxygen at different rates. e.g., Sodium (Na) and potassium (K) catch fire, if left in open. Hence, these are the most reactive metals. To prevent accidental fires, these metals are kept immersed in kerosene oil. Magnesium burns in air only by heating. So, it is less reactive than sodium and potassium. Copper (Cu) does not burn on heating but blister copper burns. Hence the order of reactivity of these metals with oxygen is :
Na >Mg> Cu.
Metals react with water to produce a metal oxide and hydrogen gas. Sodium (Na) and potassium (K) react violently with cold water. So the reaction is violent and exothermic. Magnesium (Mg) does not react with cold water. It reacts with hot water. Metals like lead, copper, silver do not react with water at all. The reactivity series of metals towards water is:
Na > Mg > Cu.

(i) X - Carbon, Y - Diamond, Z - Graphite
(ii) Non-metal
(iii) Tin.

The major differences between an electric motor and generator are stated below:
Electric Motor:
1. It converts electrical energy into mechanical energy.
2. It needs electrical energy for its works.
3. They are used as water pumps, marble grinders etc.
Generator:
1. It converts mechanical energy into electrical energy
2. It needs mechanical energy for its working.
3. They are used as water pumps, marble grinders etc.
4. diesel generator, hydro-electric generator are the examples of it.

(i)The glottis is gaurded by epiglottis because it prevents the entry of food in wind pipe. If the food enters wind pipe, then it chokes it, leading to the death of the person.
(ii)The lung alveoli are covered with blood vessels because the oxygen that we inhale dissolves in the blood, present in these blood capillaries only, as it reaches the lungs.
(iii)The wall of trachea is supported by cartilage rings because these rings prevent the air passage from collapsing.

(i) Oxygen enters the human body through the nasal passage and reaches the lungs.
(ii) Numerous alveoli are present in the lungs. These alveoli are surrounded by many blood capillaries. From the alveoli, 0₂ is taken up by the red blood cells present in the blood capillaries.
(iii) Similarly, the CO₂ from the various tissues is transported to the alveoli.
(iv) This CO₂ is then released through the nasal passage during exhalation. Alveoli are the sites of exchange of gases. Each lung contains 300- 350 million alveoli.
These alveoli increase the surface area for gaseous exchange, making the process of respiration more efficient.

(a) The solar cells are costly and hence the energy available from them expensive.
(b) 15 km/h is the minimum wind velocity required to obtain useful energy with a windmill.
(c) Nuclear fission is the process in which a radioactive atom splits up into smaller nuclei when struck with low energy neutrons.

(a) The solar cooker box is covered with a plane glass plate so as to prevent heat from escaping.
(b) Sun is said to be the ultimate and the original source for most of the energy present on the earth. When sun rays fall on oceans and other water bodies, the water present in the water bodies gets evaporated and rises up in the atmosphere. In the upper part of the atmosphere, this water vapour gets condensed and forms douds, which give rain on the high lands. Therefore, the rain water runs over the Sand surface towards the large water bodies. This running water over the land surfaces is called river. Therefore, the energy of running water actually originates from the solar energy. This is why solar energy of water flowing in a river is considered to be an indirect form of solar energy.
(c) The fission of nucleus is brought about by splitting the nucleus of heavy atoms, such as uranium or plutonium, with low-energy neutron bombardment. 

Voluntary actions are under the control of our will, it needs thinking. e.g. talking, walking. Involuntary actions are not under the control of our will, they are automatic. eg. salivation, heart beat.

(a)
  
(b) Electric current flowing through a bulb = \(\frac { Power\quad of\quad the\quad bulb }{ Voltage\quad across\quad the\quad bulb } \)
\(i.e.,\quad I=\frac { P }{ V } \)
Therefore, \({ I }_{ 60 }=\frac { 60W }{ 220V } =\frac { 3 }{ 11 } A\quad and\quad { I }_{ 40 }=\frac { 40W }{ 220V } =\frac { 2 }{ 11 } A\)
Therefore, total current flowing through the circuit  \(={ I }_{ 60 }+{ I }_{ 40 }=\frac { 3 }{ 11 } +\frac { 2 }{ 11 } =\frac { 5 }{ 11 } A=0.45A\)
(c) Total energy consumed = Power \(\times \) Time
      That is, E = P \(\times \) T
                      = (40W+60W)\(\times \)1h
                    = 100 Wh
                    = 0.1 kWh

The small intestine is the main region for the absorption of digested food. The inner lining of the small intestine is covered by millions of tiny finger-like projections called villi. The presence of villi gives the inner walls of the small intestine a very large surface area for the absorption of digestad food.

(i) Solar constant of sun is 1.4 kW/m².
(ii) Concave mirrors are used in box type solar cookers.
(iii) It is difficult to use hydrogen as a source of energy because it has not been possible to control nuclear fusion reaction. Thus, it has not yet been possible to use energy generated from fusion reaction for anything constructive.
(iv) Fossil fuels are classified as non-renewable sources of energy because it takes a long time for them to replenish naturally. It takes millions of years for fossil fuels to replenish. With the rate at which humans are using them, they will get exhausted in the next hundred years. Thus, fossil fuels are termed as non-renewable source of energy.