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.
|Maharashtra Class 8|
General Science Solution
Composition of matter
(1.) Choose the appropriate option and rewrite the following statements.
a.) The intermolecular force is …….. in the particles of solid.
Ans. iii. maximum
b.) Solids retain their volume even when external pressure is applied. This property is called …….. .
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 …….. .
Ans. iii. Element.
e.) Milk is an example of type of matter called …….. .
ii.) homogeneous mixture
iii.) heterogeneous mixture
Ans. iii. heterogeneous mixture.
f.) Water, mercury and bromine are similar to each other, because three are …….. .
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.
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%):-
(i) It is microbiological.
(ii) Hyper meteorite impact.
Dead Sea (33.7%)
(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