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Science Define :

[ Question Bank ] - 2022 · Maharashtra Board STD 10 (MSBSHSE - English Medium). 26 questions.

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26 questions · self-marked practice — reveal the answer and mark yourself.

Question 12 Marks
Write scientific reason.
Adding zinc particles to a solution of copper sulphate makes the blue solution colorless.
Answer
1. Zinc is more reactive than copper.
2. Therefore, zinc displaces copper from copper sulphate solution.
$
\underset{\substack{\text { Copper } \\ \text { sulphate }}}{ CuSO _{4( aq )}}+\underset{\text { Zinc }}{ Zn _{( s )}} \longrightarrow \underset{\substack{\text { Zinc } \\ \text { sulphate }}}{ ZnSO _{4( aq )}}+\underset{\text { Copper }}{ Cu _{( s )}}
$
3. The blue colour of copper sulphate solution fades due to the formation of colourless zinc sulphate. Hence, adding zinc particles to a solution of copper sulphate makes the blue solution colorless.
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Question 22 Marks
Give scientific reason.
It takes time for pieces of Shahabad tile to disappear in HCl, but its powder disappears rapidly.
Answer
  1. The rate of a chemical reaction depends upon the size of the reactant particles taking part in the reaction.
  2. Smaller the size of the reactant particles, higher is the rate of reaction.
  3. The size of reactant particles is more in pieces of Shahabad tile as compared to powder of Shahabad tile.
  4. When $HCl$ is added to pieces of Shahabad tile, the $CO_2$ effervescence is formed slowly. However, when $HCl$ is added to Shahabad powder, the $CO_2$​​​​​​​ effervescence is formed at a faster rate.
    Hence, it takes time for pieces of Shahabad tile to disappear in $HCl$, but its powder disappears rapidly.
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Question 32 Marks
Give scientific reason.
When the gas formed on heating limstone is passed through freshly prepared lime water, the lime water turns milky.
Answer
1. When limestone is heated, calcium oxide and carbon dioxide gas are formed.
$
\underset{\substack{\text { Calcium } \\
\text { carbonate }}}{ CaCO _{3( s )}}+\text { Heat } \longrightarrow \underset{\substack{\text { Calcium } \\
\text { oxide }}}{ CaO _{( s )}}+\underset{\begin{array}{c}
\text { Carbon } \\
\text { dioxide }
\end{array}}{ CO _2 \uparrow}
$
2. When carbon dioxide gas is passed through freshly prepared lime water, the solution turns milky due to the formation of calcium carbonate, which is insoluble in water.
$
\underset{\substack{\text { Calcium } \\ \text { hydroxide }}}{ Ca ( OH )_{2( aq )}}+\underset{\substack{\text { Carbon } \\ \text { dioxide }}}{ CO _{2( g )}} \longrightarrow \underset{\substack{\text { Calcium } \\ \text { carbonate }}}{ CaCO _{3( s )}}+\underset{\text { Water }}{ H _2 O _{( l )}}
$
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Question 42 Marks
Give scientific reason.
It is reccommended to use air tight container for storing oil for long time.
Answer
  1. When edible oil is left aside for long time, it undergoes air oxidation.
  2. Due to this, the taste and smell of oil changes and it becomes rancid. If food is cooked in this oil, its taste also changes.
  3. Thus, the oil will become unfit for consumption.
  4. The process of oxidation reaction of oil can be slowed down by storing it in air tight container.
    Hence, it is recommended to use air tight container for storing oil for long time.
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Question 52 Marks
Write scientific reason.
Always paint grills of doors and windows before using them.
Answer
  1. Grills of doors and windows are generally made up of iron metal.
  2. Before painting, iron metal is in direct contact with the moisture in the atmosphere.
  3. Moist air attacks the surface of iron metal and causes rusting (i.e., corrosion of iron).
  4. Contact between iron and moist air can be avoided by applying paint on grills of doors and windows. This prevents rusting and protects them from damage.
    Hence, grills of doors and windows are always painted before they are used.
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Question 62 Marks
Write an Explanation.
Power of accommodation
Answer
The capacity of the eye lens to change its focal length as per need is called as its power of accommodation.
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Question 72 Marks
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Magnification
Answer
Magnification due to a lens is the ratio of the height of the image to the height of the object.
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Question 82 Marks
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Farthest distance of distinct vision
Answer
The farthest distance of an object from a normal human eye, at which it is clearly visible without stress on the eye is called as farthest distance of distinct vision.
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Question 92 Marks
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Minimum distance of distinct vision
Answer
The minimum distance of an object from a normal human eye, at which it is clearly visible without stress on the eye is called as minimum distance of distinct vision.
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Question 102 Marks
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Principal axis
Answer
The imaginary line passing through both centres of curvature is called the principal axis of the lens.
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Question 112 Marks
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Electronegativity
Answer
The tendency of an element to form an anion by gaining electron in a valence shell is called electronegativity.
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Question 122 Marks
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Focal length
Answer
The distance between the optical centre and principal focus of a lens is called its focal length.
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Question 132 Marks
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Electropositivity
Answer
The tendency of an atom of an element to form cation by losing its valence electrons is called electropositivity of that element.
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Question 142 Marks
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Alkyne
Answer
The unsaturated hydrocarbons whose structures contain a carbon-carbon triple bond are called alkynes.
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Question 152 Marks
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Principal focus
Answer
Rays travelling parallel to the principal axis of a lens, after refraction, converge to a point on the principal axis or diverge in such a way that they appear to be coming out of a point on the principal axis. This point is called the principal focus of the lens.
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Question 162 Marks
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Atomic radius
Answer
For an isolated atom, the distance between the centre of the nucleus of the atom and the outermost shell is called its atomic radius.
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Question 172 Marks
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Alkene
Answer
The unsaturated hydrocarbons containing a carbon-carbon double bond are called alkenes.
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Question 182 Marks
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The optical centre of the lens
Answer
The point inside a lens on the principal axis, through which light rays pass without changing their paths is called the optical centre of a lens.
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Question 192 Marks
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Endothermic reaction
Answer
The chemical reactions which are accompanied by absorption of heat are called endothermic reactions.
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Question 202 Marks
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Period
Answer
The seven horizontal rows in the modern periodic table are called as periods.
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Question 212 Marks
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Alkane
Answer
The saturated hydrocarbons containing only single bonds between carbon atoms are called alkanes.
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Question 222 Marks
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Centre of curvature of the lens
Answer
The centres of spheres whose parts form surfaces of the lenses are called centres of curvatures of the lenses.
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Question 232 Marks
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Critical angle
Answer
For a particular value of i (angle of incidence) for which, the value of r (angle of refraction) becomes equal to 90°, is called the critical angle.
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Question 242 Marks
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Balanced equations
Answer
A chemical equation in which the number of atoms of the elements in the reactants is same as the number of atoms of those elements in the productsis called a balanced chemical equation.
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Question 252 Marks
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Group
Answer
The eighteen vertical columns in the modern periodic table are called as groups.
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Question 262 Marks
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Persistence of vision
Answer
The phenomenon that allows the image formed on retina to remain imprinted there for $\frac{1}{16}$ th of a second after the object is removed from the front of the eyes is called as persistence of vision.
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