General science class 7 Punjab textbook in pdf download. 7th class science book pdf English medium. Complete book with colorful printing in soft copy. Grade 7 general science notes subjective and objective. This book is an updated edition by Punjab Text Board.
7th Class General Science Book PTB:
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- Human Organ Systems
- Transport in Human and Plants
- Reproduction in Plants
- Environment and Feeding Relationships
- Structure of an Atom
- Physical and Chemical Changes and Processes
- Transmission of Heat
- Dispersion of Light
- Sound Waves
- Circuits and Electric Current
- Investigating the Space
- Why do we use cooking pots made of metals?
Ans: We use cooking pots made of metals because they are good conductors of heat.
- What is convection current?
Ans: The upward movement of warm water and downward monument of colder water is called a convection current.
- Which surface does absorb maximum heat?
Ans: The black surface absorbs maximum heat.
- Why do we use woollen clothes during winter days?
Ans: we use woollen clothes and blankets on winter days because they slow down the transfer of heat.
- What is the advantage of the gliding flight for a bird?
Ans: The advantage of the gliding flight for a bird is that during a gliding flight a bird does not move its wings but glides on wind currents and saves a lot of energy.
- What is convection? How does it occur?
Ans: The transfer of heat in which molecules of a medium move to the source of heat energy to absorb heat and then move away from it is called convection.
- Define thermal energy?
Ans: The energy of the motion of particles matter is called thermal energy.
- What is the meaning of thermal?
Ans: The meaning of thermal is heat.
9. How does heat flow?
Ans: Heat flows an object of higher temperature to an object of lower temperature.
- Explain transmission of heat?
Ans: The transfer of heat from one object to the other is called the transmission of heat.
- In which medium heat transfer?
Ans; Solids, liquids, and gases.
- How particles are held in solids?
Ans: In solids, particles are held very close to each other.
13. Explain good conductor?
Ans: Materials that allow heat to flow through them easily are called good conductors of heat.
- Give examples of good conductors?
Ans: Solids such as metals are good conductors are of heat.
- Define bad conductors?
Ans: Materials that do not allow heat to flow through them easily are called bad conductors.
- Examples of bad conductors?
Ans: Solids like wood, glass, plastics are bad conductors of heat.
- Which liquid is a good conductor of heat?
Ans: Mercury is a good conductor of heat.
- Which insulating material is used in the walls of the refrigerators?
Ans: Styrofoam is used between the double walls of the refrigerators.
- Examples of the effect of convection.
Ans: Winds and ocean currents are examples of the effects of convection.
19. Define radiations?
Ans: The transfer of heat from a hot body to a cold body directly without heating the space in between the two bodies is called radiation.
- Which medium is required for the heat from the sun or heater to us by radiation?
Ans: No medium is required.
- Do good absorbents of heat are also good radiators of heat?
Ans: Yes, a good absorbed of heat is also a good radiator of heat.
- Which surface is a good absorbed and a good radiator of heat, black or shiny?
Ans: The black surface is a good absorbed and radiator.
- Why fins at the back of refrigerators are painted black?
Ans: Fins at the back of the refrigerators are painted black to emit heat.
How vacuum is created in a vacuum flask?
Ans: Vacuum flask is two-walled. The air between the two walls is removed to create a vacuum.
25. How does a vacuum flask reduce the transfer of the heart?
Ans: Vacuum reduces the transfer of heat by conduction, convection and radiation.
Ans: The transfer of heat in which molecules of a medium actually move to the source of heat energy to absorb heat and then move away from it is called, convection.