NCTB Class 7 Science Chapter 14 “ Change of Climate” Solution

Bangladesh Board Class 7 Science Solution Chapter 14 “Change of Climate” Solution  Exercises Question and Answer by Experienced Teacher.

NCTB Solution Class 7 Chapter 14““Change of Climate”

Board	NCTB Bangladesh Board
Class	7
Subject	Science
Chapter	Fourteen
Chapter Name	“Change of Climate”

Fill in the gaps:-

(1) Eleven kilometres from the earth’s surface of the atmosphere is called —-.

Answer:-  Troposphere.

(2) ——- saves s from harmful rays of the sun.

Answer:- Ozone gas.

(3) The overall weather of an area for many years is the —-.

Answer:- Climate.

(4) The main role is played in climate change by —–.

Answer:- Sun.

(5) If temperature increases sea water level also —–.

Answer:- Increases.

Short answered questions:-

(1) Explain why concentration of air is more in Lowest or nearest layer of atmosphere.

Answer:- The concentration of air is more in lowest or nearest layer of atmosphere because this layer contains most of the essential gases and in this layer clouds, wind, fog etc happen, as a result contains more air.

(2) Why is troposphere most important?

Answer:- Maximum essential factors, such as oxygen, nitrogen and carbon dioxide are present in this layer. All the activities that influence the life of man and other organisms in this layer such as cloud, brain, wind etc. So troposphere is most important layer.

(3) Explain the water cycle with diagrams.

Answer:- Water from the earth’s surface is converted to water vapour from water vapour to cloud, from cloud water returns to the earth’s surface as rain. Rain water flows to the river and ultimately to the sea. Return of water is cyclic order is called water cycle.

(4) How balance of oxygen and carbon dioxide is maintained in the atmosphere?

Answer:- Living organisms take oxygen from the atmosphere for respiration. During of respiration they release carbon dioxide in the atmosphere. The plants absorb carbon dioxide for producing food and release oxygen. In this way balance of oxygen and carbon dioxide is maintained in the atmosphere.

(5) What is Green House Effect? How can global warming be explained with its help?

Answer:- After increase of temperature, heat can not go out through glasses of green house, as a result glass houses remain warm during night and the plants inside remain alive. The phenomenon of retention of heat in the glass house is called green house effect. If we compare earth with green house and carbon dioxide, methane, water vapour of atmosphere with green house gases. Due to the increase of carbon dioxide retains increased the amount of heat. So the temperature of earth is increasing. This phenomenon is called global warming.

Multiple choice questions:-

(1) Which layer of the atmosphere is nearly vacuum?

Answer:- (d) Thermosphere.

(2) In case of weather and climate —-

Answer:-  (c) (i) and (ii).

Observe the Stem and answer question no. 3 and 4.

(3) In the ‘T’ layer of the stem there is —–

Answer:- (a) (i) and (iii).

 (4) If temperature increases in ‘S’ layer of the stem —

Answer:- (c) (ii) and (iii).

(1) Creative questions:-

(a) What is underground water?

Answer:- A portion of rain water goes down under the soil and makes a reservoir which is called underground water.

(b) Describe why stratosphere is important.

Answer:- Stratosphere layer contain one gas named Ozone which protects us from sun’s harmful rays. So stratosphere is important.

(c) How do ‘Y’ and ‘Z’ maintain balance of oxygen and carbon dioxide in the environment? Explain.

Answer:- Living organisms like animals take oxygen from the atmosphere for respiration and releases carbon dioxide during respiration. The plants (Y) absorb this carbon dioxide for producing food and relax oxygen. In this way ‘Y’ and ‘Z’ maintain the balance of oxygen and carbon dioxide in the environment.

(d) If the quantity of gas expelled from Z increases, what disaster will happen in the environment? Explain.

Answer:- If the quantity of gas expelled from ‘Z’ increased the amount of heat. So the temperature of earth is increased and global warming will happen.

(2) Highest and lowest temperature of Dhaka for one year (from January to December) has been shown in the graph below:

(a) What are the factors of weather?

Answer:-  The factors of weather are temperature, pressure, wind.

(b) Why is the atmosphere in March in Bangladesh soothing?

Answer:- The atmosphere in March in Bangladesh is soothing because in this time, weather become less cold and gradually becomes hot, so it is a pleasant weather.

(c) As per the graph, in which month air in Dhaka was the highest? Explain.

Answer:- As we know when air temperature is low, then air pressure is higher. In January in pressure in Dhaka was the highest because in January air temperature is low as per the graph.

(d) In which month was there highest possibility of storm in Dhaka? Explain it in the light of the graph.

Answer:- In April there was highest possibility of storm in Dhaka. This type of storm called nor-waster comes and air pressure is high in Dhaka due to temperature is less hot. So air carries a large amount of water vapour and it becomes cold and rains.