Science:2014:CBSE:[Delhi]:Set–I

There are 18 vertical columns in the modern periodic table. These columns are called groups.

(i) Genetics is the study of mechanism by which variations are created and inherited.

(ii) Evolution is used to study the development of new type of organisms from the existing ones.

Water is a valuable resource. Following measures can be taken to save this resource:
i. Turn off the taps when not in use.
ii. Check for water leakage in the pipelines and get it repaired.

Vegetative propagation is an asexual mode of reproduction in plants in which vegetative parts of plants such as leaf, stem, or roots produce new plants under favourable conditions.

Advantages of vegetative propagation:
• Seedless Plants are propagated by this method. For example: Sugar-cane, Potato, etc.
• The important parental traits (character) are transferred without being modified to offspring and perpetuate in the population.

In the figure, i shows angle of incident and r shows the angle of reflection.

Government of India is imposing a ban on the use of polythene bags because they are non-biodegradable substance. Because of this nature, they remain in the soil for long duration and releases toxic by-products in the environment that keep leaching from them. Being waterproof in nature, they do not permit water to seep in. These polythene bags become the reason for the death of stray animals when these animals accidentally eat polythene bags.
Jute and cloth bags can be used in place of polythene bags.

The advantages of using cloth and jute bags are as follows:

• Being biodegradable, they are environment-friendly.
• They are renewable and can be easily recycled.
• They can be used again and again.
Thus, using jute and cloth bags will help to reduce pollution.

<span style="font-size:16.0pt;line-height:115%; font-family:" verdana","sans-serif";mso-fareast-font-family:"times="" new="" roman";="" mso-fareast-theme-font:minor-fareast;mso-bidi-font-family:"times="" mso-bidi-theme-font:minor-bidi;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">Biodiversity means the variety of living organisms present in the given ecosystem. For example, forest is an ecosystem. Biodiversity of a forest includes all the microbes, flora and fauna of a forest. It can be measured by counting the number of species found in an ecosystem.

Advantages of conserving forest:
(i) It keeps a check on soil erosion and floods.
(ii) It regulates the water cycle.
(iii) It produces raw materials for various industries like timber, etc.

Advantages of conserving wildlife:
(i) It preserves various species of organisms and thus, maintains species diversity.
(ii) An ecological balance is maintained by conserving wildlife.

Functional group is an atom or a group of atoms present in a carbon compound, which largely determines its properties.

Ethanol (CH₃CH₂OH) has alcoholic group(–OH) as functional group present in it.

Ethanoic acid (CH₃COOH) has carboxylic acid group (–COOH) as functional group present in it.

The addition reaction with hydrogen is characteristic property of unsaturated hydrocarbons that is alkenes and alkynes. The general formula of alkenes is C_nH_2n and that of alkynes is C_nH_2n-2

The essential conditions for these reactions to occur are

1. Presence of at least one double or triple bond in the hydrocarbon

2. Presence of catalyst like nickel or platinum.

(i) The valency of oxygen is 2 and that of group 1 elements is 1. If the element of group 1 is represented by M then the formula of oxides of group 1 elements will be M₂O.

(ii) The valency of halogens is 1 and that of group 13 elements is 3. If the element of group 13 is represented by M and halogen by X, then the formula of halides of the elements of group 13 will be MX₃.

(iii) The valency of group 2 elements is 2 and that of group 16 elements is also 2. If the element of group 2 is represented by A and that of group 16 by B, then the formula of compound formed when an element of group 2 combines with an element of group 16 will be AB.