Class 8 Science PA1 Class Test Exam Paper 2025 With Solution

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Class 8 Science PA1 Class Test Exam Paper 2025 With Marking Scheme

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Class 8 Science PA1 Class Test Exam Paper 2025 Question Paper

PA1 EXAMINATION – 2025–26
SUBJECT: SCIENCE
CLASS: VIII
MARKS: 40
TIME: 1.5 HOURS

The question paper is divided into two sections:

Detailed assessment marks: 10 marks

Descriptive/Subjective type questions: 30 marks.

General Instructions:

This question paper consists of 11 questions in 3 sections.
All questions are compulsory. However, an internal choice is provided in some questions. A student is expected to attempt only one of these questions.
Section A consists of 5 questions carrying 2marks each.
Section B consists of 4 questions carrying 03 marks each. Answers to these questions should in the range of 30 to 50 words.
Section C consists of 2 Long Answer type questions carrying 04 marks each. Answers to these questions should in the range of 50 to 80 words.

SECTION A – Class 8 Science PA1 Class Test Exam Paper 2025

What does NSC stand for? What role does it play in agriculture?
What are crops? Name two types of crops based on their growing season.
Complete the following equations:
a) CO₂ + H₂O → __________
b) 2Na + 2H₂O → __________ + __________
How does sodium metal react with water?
Name two metals that do not react with water.
What is a vaccine? Name two diseases that can be prevented by vaccines.
OR
What are communicable diseases? Give two examples of communicable diseases in animals.

SECTION B – Class 8 Science PA1 Class Test Exam Paper 2025

What are the different ways in which we can protect crops from weeds and pests?
Explain with examples how an object can be charged by friction.
How does a lightning conductor protect a building from lightning strikes?
What are the various ways to protect crops from weeds and pests?
OR
How can we ensure an increase in crop yield?

SECTION C – Class 8 Science PA1 Class Test Exam Paper 2025

What happens in the following cases?
a) When vinegar is added to baking soda
b) When carbon dioxide is passed through lime water
c) When potassium reacts with water
d) When sodium reacts with aluminium sulphate
What are fertilizers? Why is it important to add fertilizers to soil?
Differentiate between natural and chemical fertilizers.
OR
i) How are microorganisms useful in the field of medicine? (Mention any two points)
ii) What are the different ways in which crops are protected from weeds and pests?

Class 8 Science PA1 Class Test Exam Paper 2025 – Marking Scheme

SECTION A (2 × 5 = 10 Marks)

1. What does NSC stand for? What role does it play in agriculture?
Ans: NSC stands for National Seeds Corporation. It plays a key role in producing and supplying high-quality certified seeds to farmers, which helps improve agricultural productivity.

2. What are crops? Name two types of crops on the basis of their growing season.
Ans: Crops are plants grown by farmers for food or other purposes. Two types are:

Rabi crops (e.g., wheat)
Kharif crops (e.g., rice)

3. Complete the equations.
Ans:
CO₂ + H₂O → H₂CO₃ (Carbonic acid)
2Na + 2H₂O → 2NaOH + H₂ (Sodium hydroxide + Hydrogen gas)

4. How does the sodium metal react with water? Give two examples of metals that do not react with water.
Ans: Sodium reacts vigorously with water, producing sodium hydroxide and hydrogen gas with heat and sometimes flame.
Equation:
2Na + 2H₂O → 2NaOH + H₂↑
Examples of non-reactive metals: Gold (Au) and Silver (Ag)

5. What is a vaccine? Name two diseases that can be prevented by a vaccine.
Ans: A vaccine is a substance that helps the body develop immunity against diseases.
Examples: Polio and Measles

What are communicable diseases? Give two examples of communicable diseases in animals.
Ans: Communicable diseases are infectious diseases that can spread from one animal to another.
Examples: Foot and Mouth Disease and Rabies

SECTION B (3 × 4 = 12 Marks)

(Answer in 30–50 words)

6. What are the various ways in which we protect crops from weeds and pests?
Ans:

Weeds are removed using weedicides or manual weeding.
Pests are controlled by using pesticides and natural predators.
Crop rotation and timely sowing also help reduce pest attacks.

7. Explain with examples how an object can be charged by friction.
Ans:
When two objects are rubbed together, electrons transfer from one to another, creating charge.
Example: When a balloon is rubbed on dry hair, it becomes charged and sticks to walls.

8. Explain how a lightning conductor can protect a building from a lightning strike.

Ans:

A lightning conductor is a metal rod placed at the highest point of a building. It is connected to a thick wire that runs down the building and goes deep into the ground.

How it works:

When lightning strikes, the conductor gives the electric charge a safe path to travel from the top of the building into the ground.
This prevents the lightning from damaging the building or causing a fire.

It’s like giving lightning a shortcut to the Earth so that it doesn’t harm anything.

9. What are the various ways in which we protect crops from weeds and pests?
(Repeated; Attempt OR)

How can we ensure increase in crop yield?
Ans:
Crop yield can be increased by:

Using high-yield variety seeds
Applying fertilizers and manure
Ensuring irrigation and protecting crops from pests
Practicing modern farming techniques

SECTION C (4 × 2 = 8 Marks)

(Answer in 50–80 words)

10. What happened when:
) Vinegar is added to baking soda
Ans:
A chemical reaction occurs between acetic acid (vinegar) and sodium bicarbonate (baking soda).
Equation:
CH₃COOH + NaHCO₃ → CH₃COONa + CO₂↑ + H₂O
(CO₂ causes fizzing and bubbling)

ii) Carbon dioxide is passed through lime water
Ans:
CO₂ reacts with lime water (Ca(OH)₂), forming calcium carbonate, which turns the solution milky.
Equation:
Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O

iii) Potassium reacts with water
Ans:
Potassium reacts even more violently than sodium, producing potassium hydroxide and hydrogen gas.
Equation:
2K + 2H₂O → 2KOH + H₂↑ + heat + flame

iv) Sodium reacts with aluminium sulphate
Ans:
Sodium displaces aluminium from aluminium sulphate due to its higher reactivity.
Equation:
6Na + Al₂(SO₄)₃ → 3Na₂SO₄ + 2Al

11. What are fertilizers? Why is it important to add them to soil? Differentiate between natural and chemical fertilizers.
Ans:
Fertilizers are substances that are added to soil or plants to supply essential nutrients required for plant growth. They can be in the form of organic (natural) or synthetic (chemical) compounds and contain key nutrients like nitrogen (N), phosphorus (P), and potassium (K), often referred to as NPK. Fertilizers help improve soil fertility and increase crop yield.

Why is it Important to Add Fertilizers to Soil?

Nutrient Deficiency Prevention: Soil may lack essential nutrients due to previous crops depleting them. Fertilizers restore these nutrients and maintain soil health.
Promote Growth: Fertilizers supply nutrients that promote healthy plant growth, root development, and flowering.
Increase Yield: Fertilizers improve the productivity of the soil and lead to higher crop yields, ensuring food security.
Soil Fertility: Regular addition of fertilizers helps in maintaining soil fertility, ensuring that crops grow efficiently and produce quality products.

Aspect	Natural Fertilizers	Chemical Fertilizers
Source	Derived from organic matter like compost, manure, or plant/animal residues.	Synthetic or manufactured, derived from chemicals or minerals.
Nutrient Content	Provides a wide range of nutrients but in small amounts.	Provides concentrated nutrients (usually NPK) in precise proportions.

i) How are microorganisms useful in the field of medicine? (2 Points)
Ans:

Microorganisms play an important role in medicine, including:

Antibiotic Production: Fungi like Penicillium and bacteria like Streptomyces produce antibiotics that treat bacterial infections.
Vaccine Development: Viruses are used to create vaccines that protect against diseases such as measles, polio, and influenza.
Probiotics: Beneficial bacteria, such as Lactobacillus, are used to restore balance in the gut, promoting digestive health.
Enzyme Production: Microorganisms are used to produce enzymes that aid in various medical treatments, such as digestive enzyme supplements.
Bioremediation: Microorganisms help in cleaning up pollutants from the environment, such as oil spills, contributing to environmental medicine.

ii) What are the various ways in which we protect crops from weeds and pests?
Ans:
To ensure healthy crop growth and high yields, crops need protection from weeds and pests. The following are the main ways to protect crops:

a. Manual Weeding:

Description: Weeds are removed manually using tools like hoes or by hand.
Advantages: Safe, eco-friendly, and ensures selective removal of unwanted plants.
Disadvantages: Labor-intensive and time-consuming.

b. Chemical Control (Weedicides):

Description: Chemical substances called weedicides are used to kill or control weed growth.
Advantages: Effective, fast, and covers large areas.
Disadvantages: Can be harmful to the environment, beneficial organisms, and soil health if overused.

Protection from Pests:

a. Chemical Control (Pesticides):

Description: Pesticides are chemicals sprayed on crops to kill or control harmful insects and pests.
Advantages: Quickly controls pest infestations.
Disadvantages: Can lead to pesticide resistance, harm beneficial insects, and contaminate the environment.

b. Biological Control:

Description: Using natural predators, parasites, or pathogens (e.g., ladybugs to eat aphids) to control pest populations.
Advantages: Eco-friendly and sustainable method.
Disadvantages: May not be as fast-acting as chemical pesticides and is specific to certain pests.