Class 8 General Science Notes: - Unit-11: Technology in Everyday Life: Solved Exercise (Short Questions and Answers)

(National Book Foundation - New Book/New Syllabus Based on National Curriculum Pakistan 2023-2024 and Onwards)

(Class 8 General Science Notes for 8th Centralized Exam 2023-2024 and onward, FDE, Islamabad)

B. Short Questions

i) What is the most important material in toothpaste?

Ans:

Alkali is the most important material in toothpaste. So brushing toothpaste neutralizes the acid which prevents tooth decay.

ii) Why does milk turn into plastic when vinegar is added to it?

Ans:

Milk contains a protein called casein when vinegar (acid) is mixed with milk. Casein molecules combine to form long-chain products called casein plastic or milk plastic. This plastic can be easily molded.

iii) What is saponification?

Ans:

When oil or fats are heated with an alkali Na0H, Sodium salts of fatty acid (Organic acid) are formed. This reaction is known as the saponification reaction.

iv) Why it is better to use a concave mirror in a solar cooker?

Ans:

Concave Mirrors are mirrors whose inner surface of a spherical section is made reflecting. After reflection from the mirror, the rays Converge to a single point in front of the mirror called the focus point.

v) What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

Ans:

Advantages:

1: solar cooker is environment friendly; as it does not consume any fuel.

2: It causes no pollution. It harnesses the power of the sun to cook food and hence the nutrients of food are not wasted.

Disadvantages:

It is slow
It cannot be used on rainy or cloudy days.
It cannot cook all kinds of food.
It cannot be used everywhere on the earth.

vi) What potential do you see for the solar cooker to be used in Pakistan?

Ans:

Pakistan has huge solar resources. Solar cookers international has rated Pakistan as the 3rd country in the world in terms of solar cooking potential, because of abundant solar (sun) energy, as solar energy is a renewable source of energy.

vii) When can wind power be used?

Ans:

Wind power can be used to produce electricity by converting the kinetic energy of air in motion (wind) into electrical energy. The power produced by a wind turbine depends on elevation, wind speed, and air temperature.

viii) Why might engineers be interested in developing wind power?

Ans:

Engineers are interested to use wind power because it is a clean and renewable source of energy. It is a low-cost source of energy. It reduces the use of fossil fuels by cutting the emission of carbon dioxide, fine particles, and other climate alternating substances in the atmosphere.

ix) If you want to install a windmill for your home, where will you place your wind turbine?

Ans:

We will place a wind turbine on the roof of our house, a high-elevation spot away from trees and the building is the best choice for the turbine.

Unit-11: Technology in Everyday Life: Solved Short Questions and Answers

Class 8 General Science Notes

Source: General Science Book (National Book Foundation, Pakistan)

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