Science Olympiad Previous Year Paper - 3 | Science Olympiad Class 8 PDF Download

Ans: (b)

Total number of persons standing = total persons on left + total persons on right - Sumer's position = 123 + 45 - 1 = 167  

Ans: (b)

If we look at the code for KEYBOARD, every letter is incremented by 2 letters, so K + 2 → M,

E + 2 → G and so on.

Coding YACHT in the same way, we get (ACEJV).

Y + 2 → A

A + 2 → C

C + 2 → E

H + 2 → J

T + 2 → V

Ans: (d)

• To find the pairs of letters in "TWINKLING", we need to check the positions of each letter in the English alphabet.
• For example, the letters 'T' (20) and 'W' (23) have 2 letters between them, which matches their positions in the alphabet.
• By analyzing all the letters, we find that there are more than five such pairs that meet this criterion.
• Thus, the correct answer is more than five pairs of letters.

Ans: (a)

• To solve the equation, we need to follow the order of operations (PEMDAS/BODMAS).
• Currently, the equation is 15 + 9 ÷ 3 – 6 × 2.
• If we swap the ÷ and ×, the equation becomes 15 + 9 × 3 – 6 ÷ 2.
• This adjustment leads to the correct calculation, resulting in 39.

Ans: (b)

18th from top which means 17 people above him.

Let P number of people be after him.

Then Jacky's position from bottom (p + 1)^th.

50 - (17 + 1) = p

p = 32

His position from the bottom (p + 1) = 33^rd.

Ans: (c)

The correct order is 1, 3, 2, 4, 5.

Key Lock Door Room Switch on

1 3 2 4 5

Ans: (b)

The pattern is

34 x 2 = 68 – 1 = 67

67 x 2 = 134 – 1 = 133

133 x 2 = 266 – 1 = 265

265 x 2 = 530 – 1 = 529

Ans: (b)

• The code shifts each letter in 'TEACHER' back by one position in the alphabet.
• For example, T becomes S, E becomes F, and so on.
• Applying the same logic to 'STUDENT': S becomes T, T becomes U, U becomes F, D becomes E, E becomes V, N becomes U, and T becomes T.
• This results in 'UOFEVUT', which is the coded form of 'STUDENT'.

Ans: (d)

We drink coffee in a cup and have soup in a bowl. Choices 2 and 3 are incorrect because they are other utensils. 

Ans: (b)

• Reema refers to her mother's husband, which is her father.
• The only son-in-law of her father would be her brother-in-law (the husband of her sister, but Reema has no sister).
• Thus, the only sister of her brother-in-law must be Reema herself, making the girl her sister-in-law.
• Therefore, the girl is Reema's sister-in-law.

Ans: (d)
Cassiopeia is visible in the northern sky during winter somewhere around (November) season early in the night.

Ans: (a)

• Statement I is true because liquids can conduct electricity when they contain ions, which are charged particles that allow current to flow.
• Statement II is incorrect because the direction of current is defined as the flow of positive charge, which is opposite to the movement of negative ions.
• Thus, only Statement I is correct, making option (a) the right choice.

Ans: (c)

• The frictional force is highest on the towel because it has a rough texture, providing more grip.
• Next is the newspaper, which also has some texture but is less effective than the towel.
• The dry marble floor has less friction compared to the towel and newspaper, as it is smoother.
• Finally, the wet marble floor has the least friction due to the layer of water, which reduces grip.

Ans: (a)
The light-year is a unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometres or 9.46 × 10¹² km.

Ans: (a)

• The intensity of light refers to how bright the light appears.
• When a parallel beam of light hits a converging lens, it focuses the light to a point.
• As the light source is moved away, the distance increases, but the beam remains parallel, so the intensity does not change.
• Thus, the intensity of light remains constant regardless of the distance of the source from the lens.

Ans: (b)
Gibbous moon refers to the condition of more than half-lighted moon but less than full moon.

Ans: (c)

• Statement I is true as Venus is often called the morning star and evening star due to its bright appearance.
• Statement II is incorrect; on Venus, the Sun actually rises in the West and sets in the East.
• Statement III is correct; Venus is often referred to as Earth's twin because of its similar size and composition.
• Statement IV is incorrect; Venus is the second closest planet to the Sun, not the third.
• Statement V is true; Venus is the hottest planet in the solar system due to its thick atmosphere trapping heat.

Thus, the correct answer is (c) I, III and V only.

Ans: (b)
During photosynthesis, carbon dioxide is used to prepare sugars and oxygen is released into the atmosphere. This helps to maintain the percentage of oxygen at around 21% and that of carbon dioxide at around 0.03% in the atmosphere.

Ans: (a)
The discharge of static electricity produces a spark.

Ans: (d)
Global warming is the increase of earth’s average temperature due to significant increase in the level of CO₂, from combustion of fuels.

Ans: (c)
Croton plants have chlorophyll but it is hidden by dark red colour pigments.

Ans: (a)

• The body travels different distances in each hour: 15 km, 30 km, and 45 km.
• In uniform motion, the body would cover equal distances in equal time intervals.
• Since the distances are increasing, it indicates that the body is not moving at a constant speed.
• Thus, the body is in non-uniform motion, but since the question asks for uniform motion, the correct answer is (a).

Ans: (d)

• Statement I is true because radiation can transfer heat through a vacuum, unlike conduction and convection which require a medium.
• Statement II is false; radiation can pass through some solids, depending on their properties.
• Statement III is true as thermal energy is indeed transferred through infra-red radiation.
• Thus, the correct combination is I and III, making option (d) the right answer.

Ans: (b)

• The correct answer is (b) because statements II and IV are incorrect.
• Statement II is false because lying on the ground during a thunderstorm is dangerous due to lightning strikes.
• Statement IV is also incorrect; the eye of the cyclone is a region of low pressure, not high pressure.
• Statements I and III are true; wind currents do result from uneven heating, and increased wind speed does lead to lower air pressure.

Ans: (a)

• Producer gas is indeed a mixture of carbon monoxide and hydrogen, making option (a) correct.
• Option (b) is true as coal tar is a by-product of coal processing.
• Option (c) is also correct since lubricating oil is derived from petroleum and is used for lubrication.
• Option (d) is accurate as gasoline is produced through the fractional distillation of petroleum.

Ans: (a)

• The amorphous forms of carbon are those that do not have a definite crystalline structure.
• From the list, lamp black, coke, coal, sugar charcoal, gas carbon, and wood charcoal are considered amorphous.
• Graphite and diamond are crystalline forms of carbon.
• Thus, there are a total of 6 amorphous forms of carbon in the given substances.

Ans: (b)

Blue green algae is a type of bacteria which is used to fix atmospheric nitrogen in soil.

Ans: (a)

Methane is a chemical compound with the chemical formula CH4 (one atom of carbon and four atoms of hydrogen). It is a Group 14 hydride and the simplest alkane, and is the main constituent of natural gas. The relative abundance of methane on Earth makes it an attractive fuel, though capturing and storing it poses challenges due to its gaseous state under normal conditions of temperature and pressure.  

Ans: (c)

Following are the advantages of using CNG and LPG as fuels: 
(a) They are more efficient. 
(b) They can be easily transported; either in cylinders or through pipelines. 
(c) They are less polluting than other fossil fuels. 

Ans: (b)

• Malarial disease is caused by Plasmodium parasite.
• Plasmodium is a genus of parasitic alveolates, many of which cause malaria in their hosts.

Ans: (b)

• The correct answer is (b) because setting of cement, respiration, and baking of a cake are all processes that involve chemical changes that cannot be reversed.
• Setting of cement involves a chemical reaction that hardens the material.
• Respiration is a biochemical process where glucose is converted into energy, releasing carbon dioxide and water.
• Baking of a cake involves chemical reactions that change the ingredients into a new product, which cannot be undone.
• In contrast, breaking a vase, drying a floor, and filling a container with milk are physical changes and can be reversed.

Ans: (c)

Natural fibres such as wool and cotton are obtained from plants and animals are not synthetic fibres. Synthetic fibres are small units of chemicals joined together in the form of chain. The chain so formed is called a polymer. Polymer is a Greek work in which 'poly' means many and 'mer' means units. Thus, polymer means 'made of many units joined together'. 

Ans: (b)

Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste.

Ans: (a)

• Bacteriophages are specific viruses that infect and replicate within bacteria.
• They attach to the bacterial cell and inject their genetic material.
• Once inside, they hijack the bacterial machinery to produce more viruses.
• This process can lead to the destruction of the bacterial cell, which is why they are important in controlling bacterial populations.

Ans: (b)

Switch off the flame of the burner. Put a lid on the frying pan to cut off contact between fuel and oxygen and the flame will go off. 

Ans: (c)

• Citrus canker is actually caused by a bacterium, not a virus. This makes option (c) the incorrect statement.
• On the other hand, anthrax is indeed a bacterial disease that can affect both humans and cattle, confirming option (a) as true.
• Clostridium botulinum is known for causing food poisoning, which validates option (b).
• Lastly, Bhendi yellow vein mosaic disease is a viral disease that affects okra, making option (d) correct.

Ans: (b)
(i) Melamine – (3) Floor tiles 
(ii) PVC – (1) Toys and containers 
(iii) Teflon – (4) Non-stick coating 
(iv) Bakelite – (2) Electrical switches

Ans: (d)
Higher the water absorption capacity, more will be the final weight. Thus, the correct order of their final weights will be : 
Wool > Cotton > Silk > Nylon.

Ans: (b)

• The abomasum is known as the true stomach of ruminants, where the digestion of food occurs more like in non-ruminant animals.
• It follows the rumen, reticulum, and omasum in the digestive system of ruminants.
• In the abomasum, enzymes and acids break down food, allowing for better nutrient absorption.
• This part of the stomach is crucial for the overall digestive process in animals like cows and sheep.

Ans: (d)

• Animal X is likely a crocodile because it lays eggs, which is typical for reptiles.
• Animal Y is probably a dog since it gives birth to live young, characteristic of mammals.
• The other options are incorrect as they misrepresent the processes of reproduction and development in these animals.
• For example, parturition refers to live birth, which applies to Y, not X.

Ans: (d)

• The correct answer is (d) because the features listed as (iii) Prehensile tail, (iv) Sticky pads, and (v) Large ears are not adaptations found in penguins.
• Penguins have adaptations like camouflage, subcutaneous fat, and a streamlined body to help them survive in cold water and catch fish.
• In contrast, a prehensile tail is more common in animals that need to grasp or hold onto things, which penguins do not.
• Thus, the options (iii), (iv), and (v) are the correct choices for features that are not adaptive for penguins.

Ans: (b)
Waste in pit Y degraded faster than that in pit X as it was without a polythene bag. Micro-organisms are not able to decompose polythene bags, plastic bottles, toys, etc.

Ans: (b)
X i s Rhizobium, a bacterium present in the root nodules of leguminous plants (Y). It has the ability to fix atmospheric nitrogen (Z).

Ans: (b)
Pasteurisation is the process of sterilisation of milk in which the milk is heated at high temperature, around 70°C for 15 to 30 seconds and then it is suddenly chilled at 5°C and stored. Vaccination is done for immunisation. Immunisation is a process by which a person becomes protected against a disease through vaccination.

Ans: (a)
Copper does not react with dilute hydrochloric acid as copper is less reactive than hydrogen and cannot displace it from the acidic solution. Zinc and magnesium metal, on the other hand, react with hydrochloric acid to make chloride salts of the respective metals, and hydrogen gas. 

Ans: (a)
Apple contains malic acids, Ant possesses formic acid and oxalic acid is present in tomatoes.

Ans: (a)

Ans: (d)

• Different characteristics accurately describe how species are distinguished from one another, so option (a) is incorrect.
• The terms exotic and endemic are used correctly in the paragraph, making option (b) incorrect.
• Option (c) is true because migratory is the correct term for species that travel long distances.
• Since options (a), (b), and (c) are all incorrect, the correct answer is option (d), which states that all of these statements are incorrect.

Ans: (a)

1. The sulphurous acid turns blue litmus paper red. This statement is true.

2. In general, metallic oxides are acidic in nature. This statement is false as they are basic in nature.

3. Generally, non-metals do not react with water, although they may be very reactive in air. Such non-metals are stored in water. For example, phosphorus is a very reactive non-metal. It catches fire if exposed to air. To prevent the contact of phosphorus with atmospheric oxygen, it is stored in water.