NCTB Class 7 Science Chapter 11 “ “Change in Surrounding and Various’’ Solution
Bangladesh Board Class 7 Science Solution Chapter 11 “Change in Surrounding and Various’’ Solution Exercises Question and Answer by Experienced Teacher.
NCTB Solution Class 7 Chapter 11“Change in Surrounding and Various Incidents”:
NCTB Bangladesh Board
|“Change in Surrounding and Various Incidents”|
Fill in the blanks:-
(1) Boiling is a —- change.
(2) Mixing sugar in tea is a —– change.
(3) Burning paper is a —- change.
(4) Infiltration is related to —- cycle.
(5) Lime stone is a —- stone.
Short answered questions:-
(1) What is physical and chemical change? Give examples.
Answer:- The change of state where ice turns to water is called physical change. Ex: boiling point of water. Such changes where one or more than one substance transforms completely into a new substance having difference properties is called chemical change. Ex: the rust come of if it is rubbed, that means rust creates. Destruction iron.
(2) What is combustion? Explain with examples.
Answer:- When substance reacting with oxygen of the air produces heat energy is called combustion.
Ex: The chemical change of wax that creates heat energy by reacting oxygen in the air.
(3) What type of change occurs while straw or gas is burnt in furnace, physical or chemical change? Give reasons for your answer.
Answer:- Chemical change occurs while straw or gas in burn in furnace. Because here the gas or straw process a huge amount of heat energy by conducting reaction with oxygen in air that helps us in cooking. It is combustion and we know that every combustion is chemical change.
(4) Discuss the importance of water cycle.
Answer:- Importance of water cycle:
(a) For water cycle, rain water goes down under the soil and makes underground water which we use for drinking, washing etc.
(b) the wind carries some water vapours’ as clouds and reach the peak of mountains clouds cool down there and form snow.
(c) In summer snow melts and come down and forms small rivers on the slopes of mountains.
(5) What are the characteristics of igneous rock, alluvial rock and metamorphic rocks?
Answer:- Characteristic of igneous rock:- It is made cooling hot mixture. Is related to physical change.
Characteristic of alluvial rock:- It is a hard rock. It is related chemical change.
Characteristic of metamorphic rock:– It is completely different from the main rock and it is related to chemical change.
Multiple choice questions:-
(1) Which one of the following is the chemical change?
Answer:- (c) Photosynthesis.
(2) ‘P’ and ‘Q’ is appropriate for –
Answer:- (d) (i), (ii), (iii)
Give the answer to the question no. 4 according to the following stem: Mr. Anis is a building contractor. Generally he uses the metamorphic rocks of limestone to increase the beauty of the building. But sometimes he uses granite which is originated from magma.
(4) What type of granite has been mention in the stem?
Answer:- (a) Igneous.
(1) (a) What is rust?
Answer:- Water mixed ferric oxide is called rust.
(b) What do you understand by “Electroplating”?
Answer:- Electroplating is a process of making layer of metal in the surface of other metal through electrolysis.
(c) Explain what type of change occurs in the reaction as mentioned in the above stem?
Answer:- Chemical change occurs in the reaction as mentioned in the above stem. In above mentioned reaction the produced substance, glucose and oxygen are completely different than reactant carbon dioxide and water. That is why it is chemical change.
(d) Between A and B of the stem which one appears in cyclic order in the environment-analyse.
Answer:- Between ‘A’ and ‘B’ of the stem ‘B’ appears in cyclic order in the environment. Plants release ‘B’ through the above mentioned reaction and preserve food for themselves. On other side, other faunas including human beings receive ‘B’ that plant already released and produce energy and release carbon dioxide which plants use to produce their foods.
(2) (a) What is the above picture about?
Answer:– The above picture is about water cycle.
(2) (b) How is alluvial rock created?
Answer:- The stored alluvium gradually transforms into hard rock through various chemical reactions with the pressure and temperature. That is how alluvial rocks is created.
(2) (c) Explain the process mentioned in the above picture.
Answer:- Here water from Ocean enter into atmosphere through transforming into vapour with the heat of ‘A’ (sun). This vapour turned into cloud after condensation and water drops of the clouds combine with each-other to form large drops that come down to the earth’s surface as rain drops.
(2) (d) Analyze the role of ‘A’ in the process shown in the picture.
Answer:- The role of ‘A’ is important in the process. Because water from pond, river and Ocean enter into atmosphere through transforming into vapour with the heat of ‘a’.