MSBSHSE Class 8 Science Chapter 6 Composition of Matter

Question 1: Choose the appropriate option and rewrite the following statements.

a. The intermolecular force is _______ in the particles of solid.

i. minimum ii. moderate iii. maximum iv. indefinite.

b. Solids retain their volume even when external pressure is applied. This property is called__________

i. plasticity ii. incompressibility iii. fluidity iv. elasticity

c. Matter is classified into the types mixture, compound and element by applying the criterion______________

i. states of matter ii. phases of matters iii. chemical composition of matter iv. all of these

d. Matter that contains two or more constituent substances is called__________

i. mixture ii. compound iii. element iv. metalloid

e. Milk is an example of type of matter called __________

i. solution ii. homogeneous mixture iii. heterogeneous mixture iv. suspension

f. Water, mercury and bromine are similar to each other, because three are ____________

i. liquids ii. compounds iii. nonmetals iv. elements.

g. Valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are _______ chemical bond/bonds between the carbon atom and one oxygen atom in the compound-carbon dioxide.

i. 1 ii. 2 iii. 3 iv. 4

Answer:

a. The intermolecular force is maximum in the particles of solid.

i. minimum ii. moderate iii. maximum iv. indefinite.

b. Solids retain their volume even when external pressure is applied. This property is called incompressibility .

i. plasticity ii. incompressibility iii. fluidity iv. elasticity

c. Matter is classified into the types mixture, compound and element by applying the criterion states of matter .

i. states of matter ii phases of matters iii chemical composition of matter iv all of these

d. Matter that contains two or more constituent substances is called compound .

i. mixture ii. compound iii. element iv. metalloid

e. Milk is an example of a type of matter called a homogeneous mixture .

i. solution ii. homogeneous mixture iii. heterogeneous mixture iv. suspension

f. Water, mercury and bromine are similar to each other, because three are liquids .

i. liquids ii. compounds iii. nonmetals iv. elements.

g. Valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are _2 __ chemical bond/bonds between the carbon atom and one oxygen atom in the compound-carbon dioxide.

i. 1 ii. 2 iii. 3 iv. 4

Question 2: Identify the odd term out and explain

a. Gold, silver, copper, brass

b. Hydrogen, hydrogen peroxide, carbon dioxide, water vapour.

c. Milk, lemon juice, carbon, steel.

d. Water, mercury, bromine, petrol.

e. Sugar, slat, baking soda, blue vitriol.

f. Hydrogen, sodium, potassium, carbon.

Answer: a. Brass is an odd one out since it is an alloy and the other metals –gold, copper or silver are elements.

b. Hydrogen is an odd one out since it is an element and the rest are compounds.

c. Carbon is an odd one since it is an element and the rest are a mixture of several elements.

d. Water is an odd one since it is an universal solvent and the others are not universal solvents.

e. Baking soda is an odd one as it is a mixture of several elements and the rest are compounds.

f. Carbon is an odd one out as it has four valence electrons in it and the rest have one valence electron only.

Question 3: Answer the following questions.

a. Plants synthesize glucose in sunlight with the help of chlorophyll from carbon dioxide and water and give away oxygen. Identify the four compounds in this process and name their types.

b. In one sample of brass, the following ingredients were found : copper (70%) and zinc (30%). Identify the solvent, solute and solution from these.

c. Sea water tastes salty due to the dissolved salt. The salinity (the proportion of salts in water) of some water bodies Lonar lake –7.9 %, Pacific Ocean –3.5%, Mediterranean sea –3.8%, Dead sea- 33.7%. Explain two characteristics of mixture from the above information.

Answer: a. Photosynthesis is a natural chemical process in which plants along with some algae and bacteria produce oxygen and glucose from water and carbon dioxide. It uses sunlight as a source of energy, which is absorbed by the chlorophyll of plants.

6CO₂ + 6H₂ O → C₆ H₁₂ O₆ + 6O₂

We can derive the four substances in this process:

1. Carbon dioxide which is an organic compound.

2. Water which is an organic compound

3. Glucose which is an organic compound

4. Chlorophyll which is an organo-metallic compound or complex compound

b. Brass is an alloy primarily made of copper with zinc. Brass as a solid solution consists of zinc and other metals as solute dissolved in copper is considered as a solvent. Hence, brass meets all the criteria of a solution.

c. Sea water tastes salty due to the dissolved salt. The salinity (the proportion of salts in water) of some water bodies Lonar lake –7.9 %, Pacific Ocean –3.5%, Mediterranean sea –3.8%, Dead sea- 33.7%. The characteristics of mixtures from the above data are:

1. The constituent substances of a mixture are a composition of 2 or more elements or compounds.

2. The proportion of constituent substances in a mixture can vary.

3. The properties of constituent substances stay back in the mixture.

Question 4: Give two examples each

a. Liquid element

b. Gaseous element

c. Solid element

d. Homogeneous mixture

e. Colloid

f. Organic compound

g. Complex compound

h. Inorganic compound

i. Metalloid

j. Element with valency 1

k. Element with valency 2

Answer:

a. Liquid element = bromine and mercury

b. Gaseous element = hydrogen and oxygen

c. Solid element = sodium and aluminium

d. Homogeneous mixture = blood plasma and mixture of sugar in water

e. Colloid = milk, butter, jelly, etc.

f. Organic compound = carbohydrates and proteins

g. Complex compound = chlorophyll and haemoglobin

h. Inorganic compound = common salt and limestone

i. Metalloid = germanium and silicon

j. Element with valency 1 = potassium and chlorine

k. Element with valency 2 = calcium and magnesium

Question 5: Write the names and symbols of the constituent elements and identify their valencies from the molecular formulae given below.

KCl, HBr, MgBr₂ , K₂ O, NaH, CaCl₂ , CCl₄ , HI, H₂ S, Na₂ S, FeS, BaCl₂

Answer:

Compounds	Name of compounds	Symbol of constituent elements	Valency of constituent elements
KCl	Potassium chloride	K, Cl	K = 1, Cl = 1
HBr	Hydrogen bromide	K, Br	K = 1, Br = 1
MgBr2	Magnesium bromide	Mg, Br	Mg = 2, Br = 1
K2 O	Potassium oxide	K, O	K = 1, O = 2
NaH	Sodium hydride	Na, H	Na = 1, H = 1
CaCl2	Calcium chloride	Ca, Cl	Ca = 2, Cl = 1
CCl4	Carbon tetrachloride	C, Cl	C = 4, Cl = 1
HI	Hydrogen iodide	H, I	H = 1, I = 1
H2 S	Hydrogen sulphide	H, S	H = 1, S = 2
Na2 S	Sodium sulphide	Na, S	Na = 1, S = 2
FeS	Iron(II) Sulfide	Fe, S	F = 2, S = 2
BaCl2	Barium chloride	Ba, Cl	B = 2, Cl = 1

Question 6: Chemical composition of some matter is given in the following table. Identify the main type of matter from their composition.

Name of matter	Chemical composition	Main type of matter
Sea water	H2O + NaCl + MgCl2 +…..
Distilled water	H2 O
Hydrogen gas filled in a balloon	H2
The gas in LPG cylinder	C4 H10 + C3 H8
Baking soda	NaHCO3
Pure gold	Au
The gas in oxygen cylinder	O2
Bronze	Cu + Sn
Diamond	C
Heated white powder of blue vitriol	CuSO4
Limestone	CaCO3
Dilute hydrochloric acid	HCl+ H2 O

Answer:

Name of matter	Chemical composition	Main type of matter
Sea water	H2O + NaCl + MgCl2 +…..	Mixture
Distilled water	H2 O	Compound
Hydrogen gas filled in a balloon	H2	Element or Molecule
The gas in LPG cylinder	C4 H10 + C3 H8	Mixture
Baking soda	NaHCO3	Mixture
Pure gold	Au	Element
The gas in oxygen cylinder	O2	Element or Molecule
Bronze	Cu + Sn	Mixture
Diamond	C	Element (allotrope)
Heated white powder of blue vitriol	CuSO4	Compound
Limestone	CaCO3	Compound
Dilute hydrochloric acid	HCl+ H2 O	Compound

Question 7: Write scientific reason.

a. Hydrogen is combustible, oxygen helps combustion, but water helps to extinguish fire.

b. Constituent substances of a colloid cannot be separated by ordinary filtration.

c. Lemon sharbat has a sweet, sour and salty taste and it can be poured in a glass.

d. A solid matter has the properties of definite shape and volume.

Answer: a. Water is composed of two elements –oxygen and hydrogen. Hydrogen is flammable, but oxygen is inflammable. Flammability refers to the ability of a combustible material with sufficient supply of oxygen to sustain enough heat energy to burn a fire even after it has been ignited. Water is made up of two atoms of hydrogen and one atom of oxygen which form an ionic compound. It does not possess the attributes of these elements because a compound doesn’t have the properties of its constituent elements. Therefore, water has its own properties that help to extinguish the fire.

b. Constituent substances of a colloid cannot be separated by ordinary filtration because the particles size in a colloid (or colloidal solution) is much bigger than the one in a true solution and surprisingly smaller than the one in suspension. The diameter is in between 1 –100nm. The ordinary filter paper size is more than 100nm because of which colloidal particles pass through the filter paper pores. For this reason, we prefer to use ultra-filter paper so that filtration of the colloidal particles takes place easily.

c. Lemon sharbat has a sweet, sour and salty taste and it can be poured in a glass because the sour taste implies the presence of an acid. If that acid is poured in a metal vessel or utensil, then acid reacts with metal and renders it poisonous for consumption. Hence, we prefer to take glass material vessels for drinking lemon juice.

d. A solid matter has the following properties of definite shape and volume due to the reasons listed below:

1) There is a strong intermolecular force of attraction between the various particles of matter.

2) Internuclear space is almost negligible between the particles of matter.

3) Particles of matter are so close to each other that they vibrate at their fixed position too.

Question 8:

Deduce the molecular formulae of the compound obtained from the following pairs of elements by the cross multiplication method.

a. C (Valency 4) &Cl (Valency 1)

b. N (Valency 3) &H (Valency 1)

c. C (Valency 4) &O (Valency 2)

d. Ca (Valency 2) &O (Valency 2)

Answer:

a. C (Valency 4) &Cl (Valency 1):

Step 1 : Let’s first write the symbols of the radicals.

C Cl

Step 2 : Then, write the valency below the respective radical.

C Cl

4 1

Step 3 : Cross-multiply symbols of radicals with their respective valency.

Step 4 : Write down the chemical formula of the compound.

CCl₄

b. N (Valency 3) &H (Valency 1)

Step 1 : Let’s first write the symbols of the radicals.

N H

Step 2 : Then, write the valency below the respective radical.

N H

3 1

Step 3 : Cross-multiply symbols of radicals with their respective valency.

Step 4 : Write down the chemical formula of the compound.

NH₃

c. C (Valency 4) &O (Valency 2)

Step 1 : Let’s first write the symbols of the radicals.

C O

Step 2 : Then, write the valency below the respective radical.

C O

4 2

Step 3 : Cross-multiply symbols of radicals with their respective valency.

Step 4 : Write down the chemical formula of the compound.

CO₂

d. Ca (Valency 2) &O (Valency 2)

Step 1 : Let’s first write the symbols of the radicals.

Ca O

Step 2 : Then, write the valency below the respective radical.

Ca O

2 2

Step 3 : Cross-multiply symbols of radicals with their respective valency.

Step 4 : Write down the chemical formula of the compound.

CaO

MSBSHSE Class 8 Science Chapter 6 Additional Questions

Question 1: What are the various states of matter?

Answer: There are five states of matter namely:

1. Solid

2. Liquid

3. Gas

4. Plasma

5. Bose-Einstein condensate

Question 2: What is the difference in ice, water and steam?

Answer: Water exists in three different physical states such as solid, liquid and gaseous. In the solid state, water usually exists in the form of ice. In the liquid state, it is simply referred to as water which is consumed by living organisms post filtration. In the gaseous state, water exists as steam or water vapour.

Question 3: What are the smallest particles of matter called?

Answer: The smallest particles of matter are called atoms which are indivisible and indestructible.

Question 4: Classify the following matter into three groups. Cold drink, air, sherbat, soil, water, wood, cement.

Answer: Given below is the classification of matter into three groups:

a) Solid: Soil, wood, cement

b) Liquid: Cold drink, sherbat, water

c) Gaseous: Air

Question 5: What is a homogeneous mixture?

Answer: When all the components of a mixture form one particular phase that have similar characteristics, it is known as homogeneous mixture.

Question 6: What are the characteristics of the states of matter?

Answer: The characteristics of the states of matter are listed as below:

Physical state of matter	Fluidity/ Rigidity/ Plasticity/ Elasticity	Volume	Shape	Compressibility	Intermolecular force	Distance between particles
Solid	Rigid/plastic/elastic	Definite	Definite	Negligible	Strong	Minimum
Liquid	Fluid	Definite	Indefinite	Very small	Moderate	Moderate
Gaseous	Fluid	Indefinite	Indefinite	Very high	Very weak	Very large

Question 7: What consists of the smallest particles of an element?

Answer: The smallest particles of an element contain identical atoms. For example, each molecule of oxygen contains two oxygen atoms in a bonded state. The smallest particles (molecules) of a compound are formed by joining two or more types of atoms to each other.

Question 8: Why is water considered as a compound?

Answer: Pure water is a compound that is formed by the chemical combination of elements such as hydrogen and oxygen. The proportion of constituent elements of water are oxygen and hydrogen, which by weight is always 8:1, irrespective of whatsoever may be the source of water. Hydrogen is an inflammable gas while oxygen gas supports combustion. However, the compound water formed by chemical combination of the gaseous elements hydrogen and oxygen is a liquid. It is neither inflammable nor does it support combustion. On the contrary, it helps to extinguish fire.

Question 9: What are organic compounds?

Answer: Organic compounds can be a member of any states of matter such as gaseous, liquid, or solid chemical compounds in which one or more atoms of carbon are covalently linked to atoms of other elements such as oxygen, hydrogen or nitrogen.

Question 10: Why is milk considered as a mixture of elements?

Answer: Milk is a mixture of water, lactose, fats, protein and some more natural substances. The proportion of various ingredients of milk is different, as per its source. The proportion of fats in cow milk is 3-5 %, while it is 6-9 % in buffalo milk. The ingredient water is naturally present in a large proportion in milk. Therefore, milk exists in a liquid state. The sweetness of milk is due to the ingredient called lactose. In other words, the properties of the constituent substances are retained in milk.

Question 11: What is a solvent and a solute?

Answer: In a salt solution, the component which is present in the largest proportion is called solvent. The other components which are in less proportion than the solvent are called solutes.

Question 12: What are inorganic compounds? Give examples.

Answer: Inorganic compounds are those chemical compounds which lack carbon–hydrogen bonds in it. These compounds ideally are not organic in nature. Some examples include carbon monoxide, carbon dioxide, carbides, carbonates, blue vitriol, limestone, etc.

Question 13: Give some examples of complex compounds.

Answer: Chlorophyll that contains magnesium, haemoglobin that contain iron, cyanocobalamine (Vitamin B-12) that contain cobalt are some examples of complex compounds.

Question 14: Define phase.

Answer: The part of matter which has a uniform composition in a mixture is known as the phase.

Question 15: How is the strength of intermolecular force in the liquid state?

Answer: The strength of intermolecular force is moderate in the liquid state. It is not strong enough to fix the particles in a definite position and hold all of them together. As a result, liquids have definite volume. However, they have fluidity and their shape is not definite but changes in accordance with the container.

Question 16: Define a heterogeneous mixture.

Answer: When the components of a mixture are distributed into two or more phases it is called a heterogeneous mixture.

Question 17: Define solution. Explain with an example.

Answer: A homogeneous mixture of two or more substances is known as a solution. For example, when a homogeneous mixture of salt and water is formed, it is called a salt solution.

Question 18: How are complex compounds formed?

Answer: Complex compounds are formed from the molecules of compounds that have a complex structure including many atoms in the centre of this structure. Some metal atoms are also included in it.

Question 19: Define dissolution.

Answer: The process of forming a solution by mixing solutes in a solvent is called dissolution. It is the process wherein a solute in solid, liquid, or gaseous phase dissolves in a particular solvent to form a solution.

Question 20: What is Colloid?

Answer: The heterogeneous mixture of water and milk in a beaker appears translucent. It means that, when light is incident on the surface of this mixture, it is partly transmitted and partly scattered. This is because the tiny particles of milk phase in this heterogeneous mixture are dispersed evenly in water phase, and the diameter of these particles is around 10^-5 m. Such a heterogeneous mixture is known as a colloid.

Question 21: Define suspension.

Answer: The heterogeneous mixture of a liquid and a solid is called a suspension. For example, when the heterogeneous mixture of water and sawdust is formed, it is referred to as suspension.

Question 22: What is the valency of an atom?

Answer: The ability of joining to each atom with a chemical bond to another atom that is indicated by a number and this number is known as valency of that atom. An atom forms as many chemical bonds with other atoms as its valency. Generally, the valency of an element remains constant in its various compounds.

Question 23: What is a molecular formula?

Answer: Molecular formula indicates the number of atoms of each of the constituent elements present in one molecule of a compound. A molecular formula includes the information regarding the symbols of all the constituent elements and their respective number as subscripts.

We hope that the above mentioned solutions of “MSBSHSE Class 8 Science Chapter 6 Composition of Matter ” will help students build a strong foundation of the different concepts mentioned in the chapter.