# NCTB Class 7 Science Chapter 7 Properties of Matter and External Effect Solution

Bangladesh Board Class 7 Science Solution Chapter 7 Properties of Matter and External Effect Solution  Exercises Question and Answer by Experienced Teacher.

### NCTB Solution Class 7 Chapter 7 Properties of Matter and External Effect:

 Board NCTB Bangladesh Board Class 7 Subject Science Chapter Seven Chapter Name Properties of Matter and External Effect

Exercises:-

 left Right Every matter Do not conduct heat Sound Is not matter Solid Has definite size and                     volume Metals on strike Do not break

(1)  What are the characteristics of matter? Explain with expels.

Ans: The characteristics of matter:

(i) volume and definite size: A solid body has volume and definite size because it occupies space.

(ii) Rigidity and flexibility:- Some matter are soft, some are hard, some are flexible and some are nonflexible.

(iii) Electrical conductivity:- Metals conduct electricity. The bulb is illuminating. As copper is an electric conductor, it transmits electricity taking from the cell and send it to the bulb and the bulb lights up.

(iv) Melting point and boiling point:- The temperature at which water begins to vaporise is called the boiling point of water. Similarly, the temperature at which ice begins to melt is called the melting point of ice.

(2) Light is one kind of matter is this statement true or false? Give reasons to defend your answer. What are the main differences among solid, liquid and gaseous substances?

Ans:- No, light is not one kind of matter. Because matters are solids, liquid and gas, but light dose not belong to one of these. Light is just a form of energy. The main differences among solid, liquid and gaseous substance  are —–

 Solid Liquid Gas (i) It has a definite size. Its size is changeable. (i) It has no size. (ii) It has less rigidity. (ii) It has no rigidity. (ii) It has no rigidity.

(3) Why is copper used in electric wires?

Ans:- Copper is used in electric wires because copper is an electric conductor. In bulb, copper wires transmits electricity talking from the cell and send it to the bulb and lights up.

(4)Explain melting point and boiling point with examples.

Ans:- Melting point: The temperature at which solid begins to melt is called the melting point of that soil.

Boiling point: The temperature at which liquid begins to vaporise is called the boiling point of that liquid.

Multiple choice questions:-

(1) Which substance has less rigidity?

Ans:- (c) Banana- Has less rigidity.

(2) Which substance, when kept in a bottle, occupy the entire space of the bottle?

Ans:- (b) Scent- When kept in a bottle, occupy entire space of the bottle.

Observe the table below and give answer of question no.3 and 4.

 Mathins mother Mathin’s Father Mathin’s grandmother Mathin Cooks in an earthen pitcher. Uses a machine made of copper wire Used a basket made of bamboo Drinks water in a glass made of glass

(3) The object used by which person as shown in the table and electric and heart conductor?

Ans:- The object used by – (b) Mathin’s father as shown in the table is an electric and heat conductor.

Creative questions:-

(1) (a) Mr. Fazlul Hoq’s mother uses an earthen oven and clay pots to cook meals. On the other hand wife used a gas oven and cooks in a cooks in an aluminium pan.

(a)  What is matter?

Ans:- That things which occupy space and have mass are called matter.

(b) What dose ‘non-metal’ mean?

Ans:-  The things which do not have definite size and volume like metal are called non-metal.

(2) (a) What is boiling point?

Ans:- The temperature at which liquid begins to vaporise is called the boiling point of that liquid.

(b) what do you mean by thermal conductivity?

Ans:-Thermal conductivity is a rate of heat which a metal can conduct in a particular time.

(c) How the substance shown in fig. X can be converted into the substance shown in fig. Z? Explain.

Ans:- The substance shown in fig x can be converted into fig Y at its melting point and the fig Y can be converted into fig-Z at its boiling point. That how the substance shown in fig X converted into fig-Z.

Updated: October 30, 2020 — 10:46 am