NCTB Class 7 Science Chapter 9 “Heat and temperature” Solution
Bangladesh Board Class 7 Science Solution Chapter 9 “Heat and temperature” Exercises Question and Answer by Experienced Teacher.
NCTB Solution Class 7 Chapter 9 “Change of Climate”
|NCTB Bangladesh Board|
“Heat and temperature”
Fill in the gaps:-
(1) Heat flows through liquid and gas by the process of —.
(2) The temperature which boils pure water and turns into vapour in normal pressure, is called the —- point.
(3) The freezing point of Celsius Scale is —– degree Celsius.
(4) The freezing point of Fahrenheit Scale is —- degree Fahrenheit.
(5) ——— of air decreases when the amount of vapour is less.
Short answered questions:-
(1) What are the differences between heat and temperature?
Answer:- The difference between heat and temperature are —-
(a) Heat is a kind of energy but temperature is the thermal condition of anything.
(b) Heat gives us the sensation of hot on cold of anything but temperature of anything measure of how much hot or cold the thing is.
(2) Why is a gap kept between two consecutive rails line?
Answer:- Gap kept between two consecutive rails of a rail line because the iron turn hot when the trains run on it and it is caused due to the friction of wheel with them, a s result the lines increase in length.
(3) We feel warm by the side of a fire. We feel warmer or hot if we keep our hand over fire. Why does that happen?
Answer:- By the process of convection the particles of air get heated and go up but do not go aside, that’s why we feel warmer or hot if we keep our over fire rather than by the side of a fire.
(4) Why do we not hold cooking hot pot with bare hand? Why do we use a piece of cloth?
Answer:- We do not hold cooking hot pot with bare hard because heat flows from places of higher temperature to places of lower temperature . Heat is conducted away to a minimum, by non-metals like cloths that why a cloth to hold the hot pot.
(5) Why does the pressure of atmosphere decrease when temperature increases?
Answer:- The atmosphere is not confined, it is open and air gets lighter and goes up when heated. So the density of a place increases, then air pressure decreases. That’s why it the temperature of a place increases, then air pressure decreases.
Multiple choice questions:-
(1) Which acts as a well absorber of atmosphere?
Answer:- (b) Water vapour.
(2) Characteristic of temperature is that it —-
Answer:- (b) Can be measured.
(3) Thermometer as shown in figure 2:
Answer:- (a) (i).
(1) Sharmin reads in class seven. One evening she feels feverish. The temperature measured in Celsius Scale is 370C. Sharmin can understand Fahrenheit Scale temperature instead of Centigrade Scale. Being anxious she goes to a doctor to measure the temperature. The doctor measuring thermometer and finds no fever.
(a) What is temperature ?
Answer:- Temperature is the thermal condition of anything. Temperature of anything measure of how much hot or cold the thing is.
(c) What was the temperature in Fahrenheit Scale at Sharmin’s body?
(d) Explain with reason whether Sharmin would go to the doctor if she knew the relation between Fahrenheit and Centigrade Scale.
Answer:- If Shamin knew the relation between Fahrenheit and centigrade Scale then she would not go to doctor. 37 c means 980 60 F which is a normal temperature of human body.
(2) Kajal observes daily activities that happen in his life very carefully. One day he saw that the lid of the cooking pot fell down due to heat. On the other hand she noticed some gaps in their door in winter season where he found no gap in the summer. Both the incidents made her thoughtful.
(a) Which matter expands more due to heat?
Answer:- Gas expands more due to heat.
(b) Why is a gap kept between two consecutive rails of a rail line?
Answer:- There is a gap between two consecutive rail of rail line because the iron rail turn hot when the trains run on it and it is caused due to the frication of what’s with them, as a results the lines increase in length.
(c) Explain the cause of incidents which Kajal observed while cooking was going on.
Answer:- The cause of incidents which Kajal observed while cooking was going on is heat. Due to heat the temperature of the cooking pot is increases and atmosphere pressure is also increased within the pot. For this atmospheric pressure the incidents happened.