std 8 - science - chapter 6 - composition of matter - question answer | class 8 science chapter 6
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class 8,8th science lesson 6 question answer,8th standard science lesson 6 question answer
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
Exercises
b. Solids retain their volume even when
external pressure is applied. This property
is called .........
i. plasticity
iii. fluidity
ii. incompressibility
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 contain two or more
constituent substances is called
i. mixture
iii. element
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
ii. compound
iv. metalloid
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
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, salt, baking soda, blue vitriol.
f. Hydrogen, sodium, potassium, carbon.
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.
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
mixtures from the above information.
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
5. Write the names and symbols of the
constituent elements and identify their
valencies from the molecular formulae
given below.
KCI, HBr, MgBr₂, K,O, NaH, CaCl₂, CCI,
HI, H₂S, Na₂S, FeS, BaCl₂
6. Chemical composition of some matter is given in the following table. Identify the main
type of matter from their.
Name of matter
Sea water
Distilled water
Hydrogen gas filled in a ballon
The gas in LPG cylinder
Baking soda
Pure gold
The gas in oxygen cylinder
Chemical composition
H₂O + NaCl + MgCl,+...
H₂O
H₂
CH+CH₂
NaHCO,
Au
0₂
Cu + Sn
C
Bronze
Diamond
Heated white powder of blue CuSO
vitriol
Lime stone
Dilute hydrochloric acid
CaCO3
HCI + H₂O
7. Write scientific reason.
a. Hydrogen is combustible, oxygen helps
combustion, but water helps to extinguish
fire.
a. C (Valency 4) & Cl (Valency1)
b. N (Valency 3) & H (Valency 1)
b. Constituent substances of a colloid cannot
be separated by ordinary filtration.
c. Lemon sherbat has 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.
8. Deduce the molecular formulae of the
compound obtained from the following
pairs of elements by the cross
multiplication method.
c. C (Valency 4) & 0 (Valency 2)
d. Ca (Valency 2) & 0 (Valency 2)
Project:
Main type of matter
Collect the wrappers of readymade food
stuff. Use the information given and
prepare a chart of foodstuff and the
ingredients in it. Procure the ingredients
available. Discuss with friends and
teacher, test the procured ingredients
with combustion test under the
supervision of your teacher. Thereby
identify the ingredients as organic or
inorganic.
.
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