Maharashtra Board Class 8 Science Chapter 6 Composition of matter Solution

Maharashtra Board Class 8 Science Solution Chapter 6 – Composition of matter

Balbharati Maharashtra Board Class 8 Science Solution Chapter 6: Composition of matter. Marathi or English Medium Students of Class 8 get here Composition of matter  full Exercise Solution.

Std	Maharashtra Class 8
Subject	General Science Solution
Chapter	Composition of matter

(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

Ans. iii. maximum

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

i.) plasticity

ii.) incompressibility

iii.) fluidity

iv.)  elasticity

Ans. ii. incompressibility

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

Ans. iv. all of these

d.) Matter that contain two or more constituent substances is called …….. .

i.) mixture

ii.) compound

iii.) element

iv.) metalloid

Ans. iii. Element.

e.) Milk is an example of type of matter called …….. .

i.) solution

ii.) homogeneous mixture

iii.) heterogeneous mixture

iv.) suspension

Ans. iii. heterogeneous mixture.

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

i.) liquids

ii.) compounds

iii.) nonmetals

iv.) elements

Ans. ii. compounds

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

Ans. ii. 2

(2) Identify the odd term out and explain.

a.) Gold, silver, copper, brass

Ans. Brass -> Brass is non-metal only.

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

Ans. Hydrogen peroxide -> Other three are present in atmosphere.

c.) Milk, lemon juice, carbon, steel.

Ans. Steel -> It is not used in facial.

d.) Water, mercury, bromine, petrol.

Ans. Bromine -> It is not liquid.

e.) Sugar, salt, baking soda, blue vitriol.

Ans. Blue vitriol – It is not solid.

f.) Hydrogen, sodium, potassium, carbon.

Ans. Carbon – Only carbon is covalent compound.

(3.) Answer the following question.

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.

Ans. Name of four compounds where are participated in process of plant synthesis-

6CO₂ + 6H₂O à C₆H₁₂O₆ + 6O₂

(i) CO₂ – Carbon Di Oxide.

(ii) H₂O – Water.

(iii) C₆H₁₂O₆ – Sugar.

(iv) O₂ – Oxygen.

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

Ans. Brass – Solution.

Copper (70%) – Solute.

Zinc (30%) – Solvent.

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 mixtures from the above information.

Lonar lake (7.9%):-

Characteristics:-

(i) It is microbiological.

(ii) Hyper meteorite impact.

Dead Sea (33.7%)

Characteristics:-

(i) Hyper saline lake.

(ii) No plants and animals can exist in it due to salines.

(4.) Give two examples each

a.) Liquid element – Mercury (Hg), Bromine (Br).

b.) Gaseous element – Nitrogen (N), Oxygen (O).

c.) Solid element- Gold, Wood.

d.) Homogeneous mixture- Air, Saline Solution.

e.) Colloid- Foam, Gels.

f.) Organic compound- alanine, Valine.

g.) Complex compound- Hemoglobin, Vitamin B12.

h.) Inorganic compound- Carbon Monooxide, Carbon Di Oxide.

i.) Metalloid- Boron, Silicon.

j.) Element with valency 1- Clorine, Flurine.

k.) Element with valency 2- Magnesium, Calcium.

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

KCl, HBr, MgBr₂ , K₂O, NaH, CaCl₂ , CCl₄ , HI, H₂S, Na₂S, FeS, BaCl₂

(7.) Write scientific reason

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

Ans. Hydrogen is combustible, oxygen helps combustion, but water helps to extinguish fire. Because, We know that water is chemical mixture to combination of hydrogen & oxygen. When two elements combine to form a compound, the properties of the compound formed are different from the properties of parent elements.

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

Ans. Constituent particles of a colloid have very small size as compare to the pores or holes of filter paper. So that filtering any colloid with filter paper will glow the colloid particle to pass through it & thus no residue is left.

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

Ans. Because the particle of solid are very closer to each other so its have a definite shape, the solid is not compressible so its have a definite volume.

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

Ans. Due to rigidity of molecules in solid they don’t flow & their shape & volume remain unchanged.

(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 (Valency1)

Ans.  C -> 4 & Cl -> 1 => Ccl₄

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

Ans. N (Valency 3) & H -> 1 => NH₄

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

Ans. C -> 4 & O -> 2 => C₂O₄

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

Ans. Ca -> 2 & O -> 2 => Ca₂O₂