Olympiad Test: High Order Thinking Skills (HOTs)- 1 - Class 8 MCQ

Sublimation of camphor is a physical change. Point 1 in the Venn diagram represents a chemical change in
which the formation of oxide takes place. Rusting of iron nail can be shown as follows :
 Fe + O₂ + H₂O --> Fe₂O₃.xH₂O
Burning of magnesium ribbon is shown as follows :
Mg + 1/2 O₂ → MgO

Here because of induction, negative charge will induce at R and positive charge at P. Here the negative charge
at R is bounded due sphere Y. Thus wherever we ground the sphere X it will remain negatively charged.

Organism X shown in the given figure is a virus.
Viruses do not have a cellular structure, they are devoid of cellular organelles and cannot reproduce by themselves. They are regarded as connecting link between non-living and living things.

The hottest part of a candle flame is the inner zone where complete combustion happens due to enough oxygen. The middle zone is less hot and luminous, emitting light due to incomplete combustion. The innermost zone is cool and dark as there's no oxygen for combustion.

Rayon or artificial silk is obtained from a natural source, wood pulp (cellulose), yet it is a man-made polymer. It possesses properties similar to that of silk. It is mixed with cotton to make bedsheets or mixed with wool to make carpets.

- Litmus paper is a simple indicator used to test the acidity or basicity of a solution.
- Behavior:
- Blue litmus paper turns red in acidic solutions. This indicates the presence of an acid.
- Red litmus paper turns blue in basic solutions. This indicates the presence of a base.
- Correct Answer: D
- This option correctly states that blue litmus turns red in an acid, and red litmus turns blue in a base, which aligns with the known behavior of litmus paper.

Synthetic fibres soak less water as compared to natural fibres. Nylon is a synthetic fibre whereas knitted wool and cotton are natural fibres. Hence, nylon absorbs less amount of water and shows the least difference in weight.

Given, ∠AOB = 120⁰

From Snell's law,
Angle of incidence = angle of reflection
So, ∠AON = ∠NOB =
120
2
60 ° = °
∠BOP = 90° – 60° = 30°
∠PBO = 180° – 120° – 30° = 30°
So, ∠OBM = ∠MBQ = 90° – 30° = 60°.

During free fall of a body, the acceleration is equal
to the acceleration due to gravity which is constant

The colour of China rose indicator turns dark pink (magenta) in acidic solutions and green in basic solutions.
Window cleaner solution contains ammonium hydroxide which is basic in nature. Hence, the colour of China rose indicator turns green in window cleaner solution. Apple juice contains malic acid. Hence, China rose indicator turns magenta in apple juice.