. Carbon has 4 electrons in its outermost shell, and needs to gain or lose 4 electrons to attain noble gas configuration. . Losing or gaining 4 electrons is not possible due to energy considerations; hence it shares electrons to form covalent bonds. .Two reasons {or large number of carbon compounds:Read more
. Carbon has 4 electrons in its outermost shell, and needs to gain or lose 4 electrons to attain noble gas configuration.
. Losing or gaining 4 electrons is not possible due to energy considerations; hence it shares electrons to form covalent bonds.
.Two reasons {or large number of carbon compounds:
Catenation: The unique ability of carbon to form bonds with other atoms of carbon giving rise to long chains of different types of compounds.
. Tetravalency: Since carbon has a valency of 4, it is capable of bonding with four other atoms of carbon or atoms of elements like oxygen, hydrogen, nitrogen, sulphur, chlorine, etc.
The reason for the formation of strong bonds by carbon is its small size which enables the nucleus to hold on to the shared pairs of electrons strongly.
The candidate may choose any two of the following rays: (i) A ray parallel to the principal axis, after reflection, will pass through the principal focus of a concave mirror. (ii) A ray passing through the principal focus of a concave mirror after reflection will emerge parallel to the principal axiRead more
The candidate may choose any two of the following rays:
(i) A ray parallel to the principal axis, after reflection, will pass through the principal focus
of a concave mirror.
(ii) A ray passing through the principal focus of a concave mirror after reflection will emerge
parallel to the principal axis.
(iii) A ray passing through the center of curvature of a concave mirror after reflection is
reflected back along the same path.
(iv) A ray incident obliquely to the principal axis towards the pole of a concave mirror is reflected obliquely; making equal angles with the principal axis
Using the ray number (iii) and (iv) we can draw the required ray diagram.
Acquired Traits:- (l) Does not bring about change in the DNA of the germ cell. (ii) Cannot be passed on to the progeny. (iii) Cannot direct evolution Examples: Acquiring knowledge, loss of weight or any other example. Inherited Traits:- (l) Brings about change in the DNA of the germ cell. (ii) Can bRead more
Acquired Traits:- (l) Does not bring about change in the
DNA of the germ cell.
(ii) Cannot be passed on to the progeny.
(iii) Cannot direct evolution
Examples: Acquiring knowledge, loss of weight or any other example.
Inherited Traits:- (l) Brings about change in the DNA of the germ cell.
(ii) Can be passed on to the progeny.
(iii) Can direct evolution.
(l) No, the structure of the eye in each of the organisms is different. (ii)Â Fossils of certain dinosaurs/reptiles show imprints of feathers along with their bones but they could not fly presumably using the feathers for insulation. . Later, they developed/evolved and adapted feathers for flight, tRead more
(l) No, the structure of the eye in each of the organisms is different.
(ii)Â Fossils of certain dinosaurs/reptiles show imprints of feathers along with their bones but they could not fly presumably using the feathers for insulation.
. Later, they developed/evolved and adapted feathers for flight, thus becoming the
ancestors of present-day birds. (OR any other suitable evidence/example)
(a) (i) Hyphae/mycelium (ii) Sporangia (b) Structures protected by thick walls. Function: They germinate into new individuals under favourable conditions.
(a) (i) Hyphae/mycelium (ii) Sporangia
(b) Structures protected by thick walls.
Function: They germinate into new individuals under favourable conditions.
Four methods of contraception: (l) Mechanical or barrier method OR Male or female condoms. (ii) Use of hormonal preparations OR Oral pills/i-pill/Saheli. (iii) Use of loop or copper-T OR IUCD. (iv) Surgical method OR tubectomy/vasectomy. Effect on health and prosperity: (i) Health of n omen is maintRead more
Four methods of contraception:
(l) Mechanical or barrier method OR Male or female condoms.
(ii) Use of hormonal preparations OR Oral pills/i-pill/Saheli.
(iii) Use of loop or copper-T OR IUCD.
(iv) Surgical method OR tubectomy/vasectomy.
Effect on health and prosperity:
(i) Health of n omen is maintained.
(ii) Parents can give more attention to their children.
(iii) More resources can be made available for the improvement in living standard.
. No. of periods: 7 . Valency across a period increases from 1 to 4, then decreases from 4 to zero. . Metallic character of elements across a period decreases. . Valency down a group remains the same. . Atomic size of elements down a group increases.
. No. of periods: 7
. Valency across a period increases from 1 to 4, then decreases from 4 to zero.
. Metallic character of elements across a period decreases.
. Valency down a group remains the same.
. Atomic size of elements down a group increases.
Four activities: (i) Reduce excessive use of natural resources like water, fossil fuels, etc. (ii) Reuse of some resources instead of wasting (throwing) them, like empty bottles. (iii) Recycle the materials like paper to reduce the pressure on existing natural resources. (iv) Changes in lifestyle, pRead more
Four activities:
(i) Reduce excessive use of natural resources like water, fossil fuels, etc.
(ii) Reuse of some resources instead of wasting (throwing) them, like empty bottles.
(iii) Recycle the materials like paper to reduce the pressure on existing natural resources.
(iv) Changes in lifestyle, personal attitudes and practice
Two advantages: (l) Recharges ground water (ii) Mitigates floods and droughts Brings rivers and wells back to life and makes more water available for use
Two advantages:
(l) Recharges ground water
(ii) Mitigates floods and droughts
Brings rivers and wells back to life and makes more water available for use
How can we contribute in maintaining the parks and roads neat and clean.
By putting wastes in proper dustbins.
By putting wastes in proper dustbins.
See lessExplain why carbon forms compounds mainly by covalent bond. Explain in brief two main reasons for carbon forming a large number of compounds. Why does carbon form strong bonds with most other elements?
. Carbon has 4 electrons in its outermost shell, and needs to gain or lose 4 electrons to attain noble gas configuration. . Losing or gaining 4 electrons is not possible due to energy considerations; hence it shares electrons to form covalent bonds. .Two reasons {or large number of carbon compounds:Read more
. Carbon has 4 electrons in its outermost shell, and needs to gain or lose 4 electrons to attain noble gas configuration.
See less. Losing or gaining 4 electrons is not possible due to energy considerations; hence it shares electrons to form covalent bonds.
.Two reasons {or large number of carbon compounds:
Catenation: The unique ability of carbon to form bonds with other atoms of carbon giving rise to long chains of different types of compounds.
. Tetravalency: Since carbon has a valency of 4, it is capable of bonding with four other atoms of carbon or atoms of elements like oxygen, hydrogen, nitrogen, sulphur, chlorine, etc.
The reason for the formation of strong bonds by carbon is its small size which enables the nucleus to hold on to the shared pairs of electrons strongly.
To construct ray diagrams, two rays of light are generally so chosen that it is easy to determine their directions after reflection from a mirror. Choose two such rays and state the path/direction of these rays after reflection from a concave mirror. Use these two rays to find the position and nature of the image of an object placed at a distance of 8 cm from a concave mirror of focal length 12 cm.
The candidate may choose any two of the following rays: (i) A ray parallel to the principal axis, after reflection, will pass through the principal focus of a concave mirror. (ii) A ray passing through the principal focus of a concave mirror after reflection will emerge parallel to the principal axiRead more
The candidate may choose any two of the following rays:
(i) A ray parallel to the principal axis, after reflection, will pass through the principal focus
of a concave mirror.
(ii) A ray passing through the principal focus of a concave mirror after reflection will emerge
parallel to the principal axis.
(iii) A ray passing through the center of curvature of a concave mirror after reflection is
reflected back along the same path.
(iv) A ray incident obliquely to the principal axis towards the pole of a concave mirror is reflected obliquely; making equal angles with the principal axis
Using the ray number (iii) and (iv) we can draw the required ray diagram.
See lessList in tabular form, two distinguishing features between the acquired traits and the inherited traits with one example of each.
Acquired Traits:- (l) Does not bring about change in the DNA of the germ cell. (ii) Cannot be passed on to the progeny. (iii) Cannot direct evolution Examples: Acquiring knowledge, loss of weight or any other example. Inherited Traits:- (l) Brings about change in the DNA of the germ cell. (ii) Can bRead more
Acquired Traits:- (l) Does not bring about change in the
DNA of the germ cell.
(ii) Cannot be passed on to the progeny.
(iii) Cannot direct evolution
Examples: Acquiring knowledge, loss of weight or any other example.
Inherited Traits:- (l) Brings about change in the DNA of the germ cell.
(ii) Can be passed on to the progeny.
(iii) Can direct evolution.
Examples: Skin colour, colour of the eyes.
See less(l) Planaria, insects, octopus and vertebrates all have eyes. Can we group eyes of these animals together to establish a common evolutionary origin? Justify your answer. (ii) “Birds have evolved from reptiles”. State evidence to prove the statement.
(l) No, the structure of the eye in each of the organisms is different. (ii)Â Fossils of certain dinosaurs/reptiles show imprints of feathers along with their bones but they could not fly presumably using the feathers for insulation. . Later, they developed/evolved and adapted feathers for flight, tRead more
(l) No, the structure of the eye in each of the organisms is different.
See less(ii)Â Fossils of certain dinosaurs/reptiles show imprints of feathers along with their bones but they could not fly presumably using the feathers for insulation.
. Later, they developed/evolved and adapted feathers for flight, thus becoming the
ancestors of present-day birds. (OR any other suitable evidence/example)
(a) Name the following: (l) Thread like non-reproductive structures present in Rhizopus. (ii) ‘Blobs’ that develop at the tips of the non-reproductive threads in Rhizopus. (b) Explain how these structures protect themselves and what is the function of the structures released from the ‘blobs’ in Rhizopus
(a) (i) Hyphae/mycelium (ii) Sporangia (b) Structures protected by thick walls. Function: They germinate into new individuals under favourable conditions.
(a) (i) Hyphae/mycelium (ii) Sporangia
See less(b) Structures protected by thick walls.
Function: They germinate into new individuals under favourable conditions.
List any four methods of contraceptions used by humans. How does their use have a direct effect on the health and prosperity of a family
Four methods of contraception: (l) Mechanical or barrier method OR Male or female condoms. (ii) Use of hormonal preparations OR Oral pills/i-pill/Saheli. (iii) Use of loop or copper-T OR IUCD. (iv) Surgical method OR tubectomy/vasectomy. Effect on health and prosperity: (i) Health of n omen is maintRead more
Four methods of contraception:
(l) Mechanical or barrier method OR Male or female condoms.
(ii) Use of hormonal preparations OR Oral pills/i-pill/Saheli.
(iii) Use of loop or copper-T OR IUCD.
(iv) Surgical method OR tubectomy/vasectomy.
Effect on health and prosperity:
See less(i) Health of n omen is maintained.
(ii) Parents can give more attention to their children.
(iii) More resources can be made available for the improvement in living standard.
Write the number of periods the Modern Periodic Table has. State the changes in valency and metallic character of elements as we move from left to right in a period. Also state the changes, if any, in the valency and atomic size of elements as we move down a group
. No. of periods: 7 . Valency across a period increases from 1 to 4, then decreases from 4 to zero. . Metallic character of elements across a period decreases. . Valency down a group remains the same. . Atomic size of elements down a group increases.
. No. of periods: 7
See less. Valency across a period increases from 1 to 4, then decreases from 4 to zero.
. Metallic character of elements across a period decreases.
. Valency down a group remains the same.
. Atomic size of elements down a group increases.
Everyone of us can do something to reduce our personal consumption of various natural resources. List four such activities based on 3-R approach.
Four activities: (i) Reduce excessive use of natural resources like water, fossil fuels, etc. (ii) Reuse of some resources instead of wasting (throwing) them, like empty bottles. (iii) Recycle the materials like paper to reduce the pressure on existing natural resources. (iv) Changes in lifestyle, pRead more
Four activities:
See less(i) Reduce excessive use of natural resources like water, fossil fuels, etc.
(ii) Reuse of some resources instead of wasting (throwing) them, like empty bottles.
(iii) Recycle the materials like paper to reduce the pressure on existing natural resources.
(iv) Changes in lifestyle, personal attitudes and practice
List two advantages associated with water harvesting at the community level.
Two advantages: (l) Recharges ground water (ii) Mitigates floods and droughts Brings rivers and wells back to life and makes more water available for use
Two advantages:
(l) Recharges ground water
(ii) Mitigates floods and droughts
See lessBrings rivers and wells back to life and makes more water available for use