WBBSE Solutions For Class 8 School Science Chapter 2 Element Compound And Chemical Reaction Structure Of Matter Long Answer Type Questions

Chapter 2 Element Compound And Chemical Reaction Structure Of Matter Long Answer Type Questions

Question 1. What do you mean by plasma?
Answer:

Plasma:

Plasma is one of the fourth fundamental states of matter. Plasma may be produced by heating a gas to an extremely high temperature.

Due to the heating of gas at very high temperatures, vigorous collisions between atoms and molecules take place as a result of which electrons are ripped off yielding electrons and ions.

So, plasma is an electrically conducting medium. Like the gaseous state, plasma does not have a definite shape or a definite volume.

Plasma is the most abundant form of matter in the universe, most of which is present in intergalactic regions and in stars including the sun.

Question 2. Indicate two similarities and two dissimilarities between isotopes.
Answer:

Two similarities between the isotopes:

1. The number of protons in the nucleus of isotopes is the same.
2. The number of extranuclear electrons in the isotopes is also the same.
3. Two dissimilarities between the isotopes:
4. The number of neutrons in the nucleus of isotopes is different.
5. Some of the physical properties of isotopes are different.

WBBSE Class 8 Structure of Matter long answer questions

Question 3. Compare solid, liquid, and gas in connection with molecular motion.
Answer:

Comparing solid, liquid, and gas in connection with molecular motion

In a gas, the average distance between the molecules is quite large compared to liquids and solids and the molecules move at very large speeds and move randomly.

During this random, chaotic movement, they collide with each other and also with the walls of the container in which they are kept. Apart from moving from one place to another (i.e., translational motion) they can rotate and vibrate.

Compared to a gaseous state, in the liquid state, the molecules are closer to one another. The force of attraction between the molecules is greater compared to that in a gaseous state. The liquid molecules can still move but their movements are somewhat restricted.

They can rotate, vibrate and move over a small distance. The attraction between the atoms or molecules in solids is very high compared to liquids and gases. As a result, the position of atoms or molecules remains fixed with respect to one another.

So atoms or molecules remain in a relatively ordered state. The atoms or molecules within a solid have no mobility (i.e., cannot move from one place to another) and cannot rotate. Each atom or molecule can only vibrate about its mean position.

Read And Learn More WBBSE Solutions For Class 8 School Science Long Answer Type Questions

Question 4. Identify isotope, isobar, and isotone in the following atoms: \({ }_6^{13} \mathrm{C},{ }_{17}^{37} \mathrm{Cl},{ }_{20}^{40} \mathrm{Ca},{ }_6^{14} \mathrm{C},{ }_7^{14} \mathrm{~N}\)
^Answer:

¹³₆Ca and ³⁷₁₇ Cl are isotopes {having the same atomic number (6) but a different mass number (13 and 14 respectively)}.
44 C and are isobar {having the same mass
number (14) but different atomic numbers (6 and 7 respectively)}.

⁴⁰₂₀Ca and ³⁷₁₇Cl are isotones {having a different atomic number (20 and 17. respectively), and different mass numbers (40 and 37, respectively) but the same number of neutrons (20)}.

Question 5. Write the differences between isotope and isobar.
Answer:

The Differences between isotope and isobar:

	Isotope		Isobar
1.	Isotopes have the same atomic number but different mass numbers.	1.	Isobars have the same mass number but a different atomic number.
2.	The chemical properties of isotopes are mostly similar.	2.	The chemical properties of isobars are different.

 

Long answer questions on elements and compounds for Class 8

Question 6. What do you mean by radical? Give two examples.
Answer:

Radical:

Sometimes, a group of atoms consisting of different elements collectively behave as a single entity during a chemical reaction.

Such a group of atoms is known as a radical. Since a radical behaves like a single entity during a chemical reaction, it has a definite valency. For example ammonium ion (NH4-) and nitrate ion (NO3)-

Question 7. Write the formula of the following: Aluminium Sodium sulfide, Cuprous chloride, Ferric fluoride, Potassium chloride, Calcium oxide, oxide, Zinc oxide.
Answer:

Question 8. Write the formula of the following: Mercuric Aluminium sulfate, Ferric sulfate, oxide, Stannous chloride, Mercurous chloride, Magnesium carbonate, and Cupric nitrate.
Answer:

Question 9. Write the formula of the following: Calcium sulfate, Calcium sulfite, Aluminium bicarbonate, Sodium hydroxide, Ammonium bicarbonate, and Ferrous nitrate.
Answer:

WBBSE Chapter 2 structure of matter detailed answers

Question 10. Mention the characteristics of an ionic compound.
Answer:

The general characteristics of an ionic compound can be summarized as follows :

1. In the case of ionic compounds, molecules do not exist. In solid-state, cations and anions are properly arranged in a definite pattern.
2. In ionic compounds, the total charges on cations will be the same as the total charges on anions.
3. Ionic compounds are generally soluble in water.
4. An aqueous solution of ionic compounds which are soluble in water conducts electricity.
5. The melting point and boiling point of ionic compounds are totally high.

Question 11. Mention the cation(s), Marion(s), formula, and Requirement for maintaining charge neutrality and calculation for a net charge for the following compounds: sodium chloride, potassium fluoride, zinc oxide, calcium oxide, calcium chloride, aluminum oxide, sodium sulfide
Answer:

 

Question 12. Mention the cation(s), anion(s), formula, and Requirement for maintaining charge neutrality and calculation for a net charge for the following compounds: ferrous chloride, ferric chloride, cuprous oxide, cupric oxide, mercurous chloride, mercuric chloride, ferrous oxide, ferric oxide, stannous chloride, stannic chloride.
Answer:

In-depth explanations of the structure of matter for Class 8

Question 13. Mention the cation(s), anion(s), formula, and Requirement for maintaining charge neutrality and calculation for a net charge for the following compounds: ferrous sulfate, aluminum sulfate, calcium bicarbonate, calcium phosphate, ammonium sulfate, cupric nitrate, magnesium carbonate, sodium hydroxide, aluminum nitrate, calcium sulfite, ammonium nitrate, ferric sulfate, magnesium hydroxide, potassium carbonate.
Answer: 

 

Question 14. Mention the characteristics of covalent compounds.

Answer:

The characteristics of covalent compounds are the following:

1. In covalent compounds, molecules exist.
2. The melting point and boiling point of covalent compounds are usually low.
3. Covalent compounds are generally soluble in organic solvents and usually insoluble in water.
4. These compounds usually exist as gas or liquid under normal temperatures and pressure.

Question 15. The atomic number of an element (Z) is 12 more than that of nitrogen. If a mass number of the atom is 39, find out the number of protons, neutrons, and electrons in the atom. Identify the element Z.
Answer:

Given:

The atomic number of an element (Z) is 12 more than that of nitrogen.

If a mass number of the atom is 39.

The atomic number of nitrogen = 7.

∴ An atomic number of element 2=7 + 12 = 19. The mass number of element Z = 39.

∴ Number of neutrons = 39-19 = 20. Hence, an atom of Z has 19 protons, 20 neutrons, and 19 extra nuclear electrons.

Z is potassium having atomic number 19 and mass number 39.

WBBSE Class 8 Science practice long answer questions on elements and compounds

Question 16. The electronic configuration of an atom of an element (Symbol M) is [ K(2), L(8), M(8), N(2)]. The number of neutrons is 20. Find out the atomic number, mass number, and valency of the element. What is the formula of the oxide of M?
Answer:

Given:

The electronic configuration of an atom of an element (Symbol M) is [ K(2), L(8), M(8), N(2)].

The number of neutrons is 20.

Total number of electrons = 2 + 8 + 8 + 2 = 20.

∴Atomic number, Z = 20

Mass number, A = 20 + 20 = 40.

Since the valence shell (N shell) contains 2 electrons, hence valency of the element (M) shall be +2.
The formula of oxide:

 

Examples of long answer questions on structure of matter for Class 8

Question 17. The formula of an oxide of a metal M is M203. Write down the formula of its chloride and nitrate.
The valencies of two elements A and B are 3 and 5 respectively. If B is solid among them what will be the formula of the compound formed when A reacts with B?
Answer:

Given:

The formula of an oxide of a metal M is M203.

The valencies of two elements A and B are 3 and 5 respectively.

From the formula of oxide (M₂O₃) it is clear that the valency of metal M is 3.

∴ Metal chloride = MCI₃ and Metal nitrate = M(NO₃)₂ Formula of compound