All questions of Science for Class 1 Exam

Introduction to Paper-Making
Paper is a versatile material used for writing, printing, and packaging. Its primary natural source is wood, which is processed to create sheets of paper.
Why Wood is Used
- Cellulose Content: Wood contains cellulose, a fibrous substance that gives paper its strength. Cellulose fibers can be broken down and reformed into a flat sheet.
- Abundance: Trees are widely available, making wood an abundant resource. Various tree species, including softwoods (like pine) and hardwoods (like birch and oak), are utilized in paper production.
- Processing: The process of turning wood into paper involves:
- Chipping wood into small pieces
- Cooking the chips with chemicals to break down lignin (the substance that binds fibers together)
- Bleaching to achieve the desired color and brightness
- Forming sheets of cellulose fibers and drying them
Alternative Sources
While wood is the primary material, paper can also be made from other plant fibers, such as cotton, hemp, and bamboo. However, wood pulp remains the most common due to its cost-effectiveness and availability.
Conclusion
In summary, wood is the correct answer for the natural material used to make paper. Its cellulose content, abundance, and the efficient processing methods contribute to its widespread use in the paper industry.

Material commonly used to make windows: Glass
Glass is the most commonly used material for making windows due to its transparency and ability to allow light to pass through. Here are some key points explaining why glass is used for windows:

Transparency:
- Glass is transparent, allowing natural light to enter buildings and provide occupants with a view of the outside.
- This transparency helps to create a bright and open living or working environment.

Durability:
- Glass is a durable material that can withstand exposure to the elements, making it suitable for use in windows.
- It is resistant to scratches and does not degrade over time.

Insulation:
- Some types of glass, such as double-glazed windows, provide insulation against heat loss and noise, improving energy efficiency and comfort.

Aesthetics:
- Glass windows can enhance the aesthetics of a building, providing a sleek and modern look.
- There are various types of glass available, such as tinted or frosted glass, allowing for customization to suit different design preferences.

Conclusion:
Glass is the preferred material for making windows due to its transparency, durability, insulation properties, and aesthetic appeal. It offers a combination of functionality and visual appeal, making it a versatile choice for both residential and commercial buildings.