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#### Question 1:

Which of these elements do plants need in addition to glucose to synthesise proteins?

(a) carbon
(b) nitrogen
(c) hydrogen
(d) oxygen

(b) nitrogen
Nitrogen is an integral part of all proteins. Therefore, plants need nitrogen in addition to glucose to synthesise proteins.

#### Question 2:

How many chambers does the stomach of a cow have?

(a) one
(b) two
(c) three
(d) four

(d) four
Stomach of a cow is complicated and has four chambers.

#### Question 1:

What kind of nutrition is seen in animals?

Heterotrophic nutrition is seen in animals.

#### Question 2:

By what methods-physical or chemical-is it possible to break a compound into its constituents?

A compound can be broken into its constituents by chemical method. For example, water can be broken down into hydrogen and oxygen by passing electricity through it.

#### Question 3:

What is the base of all vegetable fibres?

Cellulose is the base of all vegetable fibres.

#### Question 4:

In which method of transfer of heat do molecules themselves travel from the hot portion to the cold portion?

Convection is the method of transfer of heat in which molecules themselves travel from the hot portion to the cold portion.

#### Question 5:

If a vegetable tastes bitter, what is it likely to have in it-a base or an acid?

If a vegetable tastes bitter, it is likely to have base in it as bases are bitter and acids are sour in taste.

#### Question 1:

Name all the ingredients that are required for photosynthesis to occur.

Photosynthesis requires carbon dioxide and water as raw materials. Photosynthesis in green plants takes place in the presence of light. Green plants have light absorbing pigment called chlorophyll.

#### Question 2:

How does solid food travel down the oesophagus after it is swallowed?

After the solid food is swallowed, it travels down the oesophagus by peristalsis, i.e., wave like action of muscles of oesophagus.

#### Question 3:

What do you mean by the 'atomicity' of an element?

Atomicity of an element can be defined as the number of atoms present in the molecule of an element.

#### Question 4:

What is sericulture?

Sericulture is the breeding and management of silk worms for the purpose of obtaining silk, i.e., silk production.

#### Question 5:

What do you mean by 'temperature' of an object?

Temperature of an object refers to the hotness or coldness of that object. Higher the temperature, hotter is the object.

#### Question 6:

Water has higher heat capacity than stone. Compare the time taken by water and stone to heat up and cool down.

Water has higher heat capacity than stone. Therefore, it takes more time to heat up and cool down as compared to stone.

#### Question 7:

What effet does excess hydrochloric acid in the stomach cause?

Excess of hydrochloric acid in the stomach causes acidity.

#### Question 8:

Give a chemical reaction in which there is evolution of gas.

Reaction of metals with acids forms salt and hydrogen gas.
Example:
Mg + 2HCl $\to$MgCl2 + H2 (gas)

#### Question 9:

What protection does a polar bear have from the extreme cold weather in which it lives?

Polar bear has a layer of fat under its skin which acts as an insulator. Further, it has two thick layers of fine fur which traps air for the protection from the extreme cold weather in which it lives.

#### Question 10:

What is weathering?

The formation of soil by the process of breaking up of large pieces of rock into smaller pieces by the action of natural agents such as water, air, glaciers and roots of the plants is termed as weathering.

#### Question 1:

Describe the structure of a villus.

The small finger-like projections present on the surface of a small intestine are called villi. The fine network of blood capillaries is present close to the surface of each villus. Food is first absorbed on the surface of a villus and then passed on to the blood capillaries.

#### Question 2:

What is the difference between a mixture and a compound on the basis of their constituents?

 Mixture Compound Ratio of the constituents is not fixed. Ratio of the constituents is always fixed. A mixture is a combination of two or more elements or compounds in which neither new molecules are formed and nor chemical reaction takes place. A compound is a combination of two or more elements or compounds in which new molecules are formed.

#### Question 3:

Why does matter expand when heated?

Matter expands when heated because on heating, movement of its molecules increases resulting in increasing the distance between the molecules. This increases the area occupied by them. Thus, the volume of the matter expands.

#### Question 4:

What happens when sulphuric acid reacts with zinc metal?

When sulphuric acid (H2SO4) reacts with zinc metal, zinc sulphate (ZnSO4) and hydrogen gas (H2) are formed. The chemical reaction is as follows:

H2SO4 + Zn $\to$ZnSO4 + H2

#### Question 5:

What is the difference between weather and climate?

 Weather Climate The daily atmospheric conditions of a place with respect to factors like temperature, rainfall, humidity etc., is termed as weather of that place. The weather pattern of a place, on an average over a long span of time like 30 years or so, is termed as climate of that place.

#### Question 3:

Which is the smallest particle of an element that can take part in a chemical reaction?

(a) atom
(b) molecule
(d) either atom or molecule depending on the element

(a) atom
Atom is the smallest particle of an element that can take part in a chemical reaction.

#### Question 4:

Cloth made out of which of these when burnt will smell like burning hair?

(a) cotton
(b) wool
(c) jute
(d) flax

(b) wool
Wool, when burnt, smells like hair because it is nothing but thick hair of animals like sheep.

#### Question 5:

At what temperature will the reading on a Celsius thermometer be the same as the that on a Fahrenheit thermometer?

(a) 0°
(b) 100°
(c) −40°
(d) 212°

(c) $-$40 ͦ
As calculated from the formula C= ($\frac{5}{9}$) (F$-$32), the temperature at which Celsius and Fahrenheit thermometer read the same is −40°.

#### Question 6:

How does the dark or light colour of an object affect the amount of heat it radiates or absorbs?

(a) Dark colour objects absorb and radiate more heat than light coloured objects.
(b) Dark colour objects absorb more but radiate less heat than light coloured objects.
(c) Dark colour objects absorb less and radiate more heat than light coloured objects.
(d) Dark colour objects absorb and radiate the same amount of heat as light coloured objects.

(a) Dark-coloured objects absorb and radiate more heat than light-coloured objects.
Dark-coloured objects absorb and radiate more heat than light-coloured objects.

#### Question 7:

Which of these is not a mineral acid?

(a) acetic acid
(b) hydrochloric acid
(c) sulphuric acid
(d) nitric acid

(a) acetic acid
Mineral acids are inorganic acids as they do not have carbon. Acetic acid is an organic acid.

#### Question 8:

If a chemical equation has '+ heat' on its right hand side, it is definitely a

(a) endothermic reaction.
(b) exothermic reaction.
(c) combination reaction.
(d) neutralization reaction.

(b) exothermic reaction
The '+ heat' on the right side of reaction shows that heat is released in the reaction. Hence, the reaction is exothermic.

#### Question 9:

Which of these soils absorbs and retains the maximum water?

(a) sandy soil
(b) clayey soil
(c) loam soil
(d) sandy-loam soil

(b) clayey soil
Clayey soil have very little space between its particles and thus, it can absorb and retain maximum water.

#### Question 10:

In a compound XO2, the valency of X is

(a)1.
(b) 2.
(c) 4.
(d) cannot be determined from this fromula.