Science: 2016: CBSE: [Delhi]: Set – I

(i) C₃H₆

(ii) C₅H₈

Buds are produced from the leaves of Bryophyllum plant for vegetative propagation.

Following are the two natural ecosystems:
a. Forest
b. River

A concave mirror can produce a magnified image

• When the object is placed between the focus and centre of curvature.
• When the object is placed between focus and pole of the mirror.

Differences betweenthe two images formed in above two cases:

• Real and inverted image is formed when the object is placed between the focus and centre of curvature.
• Virtual and erect image is formed when the object is placed between the focus and centre of curvature.

The four advantages of properly managed watershed management are:
i. It helps to maintain equal and sustainable distribution of water.
ii. It enhances the level of groundwater.
iii. It maintains the quality of water.
iv. It provides protection from floods by controlling the flow of rainwater.

Active participation of local people helped to conserve forestsand wildlife.The followingare the examples:

i. In 1731, Amrita Devi Bishnoi from Khejri village established a group of 363 people who sacrificed their lives for the protection of khejri trees.

ii. In 1970, SunderlalBahuguna initiatedChipkoAndolan, in which women hugged the tree trunks with their arms, thereby preventing the workers from cutting down the trees.

iii. In 1972, the forest officer (A.K. Banerjee) along with the people of local community recovered the badly degraded Sal forests of Arabari.

Covalent compounds are those compounds which are formed by sharing of electrons between two atoms or the compounds which contain covalent bonds.

Covalent compounds are different from ionic compounds because the ionic compounds are formed by the transference of electrons.

Three characteristics of covalent compoundsare as follows:

(i)Generally they have low melting and boiling points.

(ii) Generally they are insoluble or less soluble in water but soluble in organic solvents.

(iii)They do not conduct electricity.

(i) The fruity smelling compound belongs to the class of esters.

The name of product is Ethyl ethanoate.

(ii) In this reaction, conc. H₂SO₄ acts as a dehydrating agent and helps in the removal of water formed in the reaction.

(i) Calcium is a metal. The reason is that, it has two electrons in its outermost shell which it can lose easily.
(ii) Potassium (atomic number 19) is placed before Calcium (atomic number 20) in the same period that is fourth period. Since the atomic radius decreases on moving from left to right in a period, the atomic radius ofcalcium is smaller than that of potassium.
(iii) The formula of oxide of calcium is CaO, because the valency of calciumas well as that of oxygen is 2.

The electronic configuration (2, 8, 2) of the element ‘M’ suggests that itbelongs to group 2 (presence of 2 electrons in valence shell) and period 3 (presence of 3 shells) of the Modern Periodic Table and its valency is 2.

The chemical formulas of three compounds are –

M (NO₃)₂ , MSO₄ , M₃ (PO₄)₂respectively.

‘M’ will form ionic compounds by losing two electrons present in the valence shell.