Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Fibers are the very thin, thread-like strands used to make clothes. When fibers are twisted together, they form yarn.
Natural Fibers are obtained from plants and animals. Examples include Cotton and Jute (from plants) and Wool and Silk (from animals).
Synthetic Fibers are man-made fibers created using chemicals in factories. Common examples are Nylon, Polyester, and Rayon.
Clothes protect our bodies from weather conditions such as heat (), cold, and rain, as well as from insect bites.
Cotton clothes are preferred in summer because they have pores that allow air to pass through and absorb sweat efficiently.
Woolen clothes are worn in winter because wool is a poor conductor of heat and traps air, keeping the body warm at lower temperatures (e.g., ).
Waterproof materials like plastic or rubber are used to make raincoats and umbrellas because they do not absorb water ().
📐Formulae
💡Examples
Problem 1:
Classify the following into Natural and Synthetic fibers: Nylon, Wool, Cotton, Polyester.
Solution:
Natural: Wool, Cotton; Synthetic: Nylon, Polyester.
Explanation:
Wool and Cotton are obtained from sheep and plants respectively (nature), while Nylon and Polyester are made by humans using chemicals.
Problem 2:
Why do we wear light-colored cotton clothes when the temperature is high, such as ?
Solution:
Cotton absorbs sweat and allows body heat to escape.
Explanation:
Cotton is a natural fiber with air spaces that help in evaporation of sweat, while light colors reflect the heat from the sun.
Problem 3:
Which fiber would be best for making a trekking rope that needs to be very strong and dry quickly?
Solution:
Nylon or Polyester (Synthetic Fibers).
Explanation:
Synthetic fibers are generally stronger and more durable than natural fibers, and they do not absorb much , allowing them to dry faster.