FIRST TERM ASSESSMENT

CHEMISTRY
Grade : 8 Max. Marks : 80
Date : 04.09.2024 No. of Questions : 07
Duration : 2 hours No. of Printed sides : 11
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Answers to this paper must be written on the answer booklet provided.
The first 15 minutes is allotted for reading the question paper.
The intended marks for questions or parts of questions are given in brackets [ ].
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SECTION A
(Attempt all questions from this section)
Question 1 [15 marks]
Select the correct answers to the questions from the given options. Do not
copy the questions. Write the correct answers only. (E.g.: i. – a. Copper)
(i) Which of the following triads do not contain covalent bonds?
(a) C2H2, H2O, CO
(b) CO, CO2, CH4
(c) NH3, N2, HCl
(d) KI, LiF, NaF
(ii) Some changes are classified as given below. Which of the following rows
give the incorrect information?
Rows Change Chemical change Reversible change
I Sliced apple turns brown No No
II Crystallization of sugar No Yes
III Cooking of vegetables No Yes
IV Photosynthesis Yes No

(a) I and III

(b) I, II and III
(c) I, II ,III and IV
(d) II and III

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(iii) In a diamond, each carbon atom is joined to …………… other carbon atoms
by ……………….. bonds.
(a) three, covalent
(b) five, ionic
(c) two, ionic
(d) four, covalent
(iv) Rohan balanced the following chemical equation incorrectly.
Which part of the equation should he correct?
2 Rb 3 H2O 2 RbOH H2
Reactant 1 Reactant 2 Product 1 Product 2
(a) Reactant 1
(b) Reactant 2
(c) Product 1
(d) Product 2
(v) The electronic configuration of an element ‘Q’ is 2,8,2. Which statements
about element Q are true?
I) It is a metal. IV) It has valency 2.
II) It is non-metal. V) It will form a cation.
III) It is an inert gas. VI) It will form an anion.
(a) I, III and V
(b) I, IV and V
(c) II and VI
(d) II, IV and V
(vi) Given below is a Lewis dot electron structure diagram. The dots represent
the valence electrons. Which diagram shows the correct representation for
the formation of O2 molecule? [Given: 8O16]

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(vii) Mr. Shah wanted to manufacture black typewriter ribbons and carbon
paper. The most suitable amorphous form of carbon that he should use
is -
(a) Gas carbon
(b) Coke
(c) Carbon monoxide
(d) Lamp black
(viii) Solids do not diffuse because -
(a) They have an infinite number of free surfaces.
(b) They lack intermolecular spaces.
(c) They have a fixed volume.
(d) They vibrate about their mean position.
(ix) Electrolysis of water (water → hydrogen + oxygen) is
generally -
(a) An irreversible, chemical change.
(b) An irreversible, physical change.
(c) A reversible, physical change.
(d) A reversible, chemical change.
(x) Identify the correct example of interconversion of states of matter in
which the particles of matter move the farthest away.
(a) Manufacture of ice lollies.
(b) Cloud formation in the sky.
(c) Melting of butter.
(d) Disappearance of naphthalene balls.
(xi) Allotropes are -
(a) same elements that have similar graded chemical properties but
different physical properties.
(b) same elements that have similar graded physical properties but
different chemical properties.
(c) different elements that have similar graded physical properties but
different chemical properties.
(d) different elements that have similar graded physical properties and
chemical properties.
(xii) Aluminium reacts with a certain nonmetallic element to form a
compound with the general formula Al2X3. The valency of X is
(a) 1
(b) 2
(c) 3
(d) 4

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 (xiii) When cooking in a pressure cooker, as pressure increases -
(a) the boiling point of water increases.
(b) the boiling point of water decreases.
(c) the boiling point of water remains the same.
(d) not enough data to predict the effect on boiling point.
(xiv) The correct valencies for Cupric and Ferric are -
(a) 1, 2
(b) 2, 3
(c) 3, 4
(d) 2, 1
(xv) ZnO + C → Zn + CO
Statement 1: Zinc oxide is reduced to zinc.
Statement 2: Carbon is oxidised to carbon monoxide.
Statement 3: Carbon is reduced to carbon monoxide.
(a) Statement 1 is true but Statements 2 and 3 are false.
(b) Statement 2 is false but Statements 1 and 3 are true.
(c) Statement 2 is true but Statements 1 and 3 are false.
(d) Statement 3 is false but Statements 1 and 2 are true.

Question 2 [25 marks]

(i) State the correct scientific term.
(Do not give examples. Write only the answers.) [5]

(a) An atom of an element or a group of atoms of different elements that

behave as a single unit with a positive or negative charge on it.
(b) The ability of carbon atoms to combine with other carbon atoms
through covalent bonds that result in large compounds containing a
chain or ring of carbon atoms.
(c) The random motion of particles suspended in a fluid due to their
collision with their fast-moving atoms or molecules in the gas or
liquid.
(d) The distribution of electrons in different orbits or shells or energy
levels of an atom.
(e) The type of reaction which involves the absorption of heat energy.

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(ii) Balance the following equations: [5]
(a) Cl2 + KBr → KCl + Br2
(b) HCl + MnO2 → MnCl2 + H2O + Cl2
(c) C2H2 + O2 → CO2 + H2O
(d) Al(OH)3 + H2SO4 → Al2(SO4)3 + H2O
(e) Mg(NO3)2 + KOH → Mg(OH)2 + KNO3

(iii) The periodic table with the first 20 elements is given below. The Lewis dot
structure is used to represent the valence electrons of the elements.
Answer the questions that follow: [5]

Note: A group is a column in a periodic table. Elements of a group have

the same number of valence electrons.
A period is a row in a periodic table. Elements in the same row have the
same number of electron shells
(a) Give the electronic configuration for Si.
(b) Give the symbolic representation for K. (n = 20)
(c) Name and give the chemical formula of the compound formed when the
element of Group 2, period two combines with the element of Group 17,
period 3.
(d) Elements of group 18 do not participate in chemical reactions.
Justify this statement.

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(iv) Rita replicated the laboratory preparation of carbon dioxide in her school
Chemistry Lab under the supervision of her teacher. Study the diagram of
her experiment carefully and answer the questions that follow: [10]

(a) Give the complete balanced chemical equation for the laboratory
preparation of carbon dioxide.
(b) The narrow end of the thistle funnel must be submerged in the
dilute hydrochloric acid. Give a reason.
(c) Rita made an error in the collection method of the gas. Why was the
method of collection of CO2 gas not suitable?
(d) What should have been the ideal method for the collection of gas?
(e) Which property of carbon dioxide would make the above method
ideal?
(f) State the special or confirmatory test performed for carbon dioxide.
(g) Write the word and chemical equation of the reaction of carbon
dioxide with calcium oxide.
(h) Write any two uses of carbon dioxide.

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 SECTION B
(Attempt any four questions from this section.)
Question 3 [10 marks]
(i) State whether the following statements are True or False.
Rewrite the false statements by changing only the underlined terms with
the correct terms: [2]
(a) 2CO is two atoms of cobalt.
(b) Cations form acid radicals.
(ii) Differentiate between the following based on the given criteria: [2]
(a) Atoms and Ions (electric charge)
(b) Carbon dioxide and Carbon monoxide (result with litmus test)
(iii) Give the chemical names of the following ionic compounds. [3]
(a) Mg3P2
(b) FeCl3
(c) Al2S3
(iv) The table below lists the names of some substances. Classify them as
molecules of elements or compounds and state the type of bonding that is
present between the atoms. [3]
Substance Molecule of element Type of Bond formed.
or compound
(1) Magnesium oxide ___________A1.________ ___________A2.________
(2) Chlorine ___________B1.________ ___________B2.________
(3) Carbon dioxide ___________C1.________ ___________C2.________

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Question 4 [10 marks]
(i) Select the correct factor from those mentioned in the brackets, that affects
the speed of evaporation in each of the examples given below: [2]
[Nature of liquid, Temperature, Motion of air, Surface area of exposure]

Figure 4 Figure 5
a) Clothes remain damp on a cold, b) Filter coffee in a narrow glass
rainy day. remains hot for a long time.
(ii) What do these symbols stand for in a chemical equation? [2]
(a) (aq) (b) ↓
(iii) Zuri was experimenting with an incomplete electric circuit, a diamond drill bit
and a graphite pencil, as shown below. Answer the questions that follow: [3]

(a) Fill in the blanks (do not rewrite):

Zuri noticed that the bulb does not glow when a ………(1)………....
[diamond drill bit/graphite pencil ] is connected between points A and B in
the circuit.
When a ………(2)………… [diamond drill bit/graphite pencil ] is connected
between points A and B in the circuit, it glows brightly.
(b) Differentiate between the diamond drill bit and graphite pencil with regard
to the presence of free electrons.
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(iv) Give a reason for each of the following statements: [3]
(1) Graphite is used as a lubricant.
(2) Making beer from barley water is a chemical change.
(3) Carbon is used for the extraction of metals like zinc and iron.
Question 5 [10 marks]
(i) The following experiment was conducted using three syringes of 100 ml
each. Study the diagram and answer the questions that follow: [3]

(1) Which piston will show the maximum compressibility?

(2) Which piston will show the least compressibility?
(3) Which property of matter is responsible for the ease of
compressibility?
(ii) State the observation in each of the following: [3]
(a) Burning of carbon monoxide gas.
(b) Iodine crystals are heated.
(c) The action of CO2 gas on acidified potassium dichromate paper.
(iii) Differentiate between Isotopes and Isobars based on: [2]
(a) their atomic number.
(b) their chemical properties.

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 (iv) Draw the orbit structure diagram for the Calcium ion and state its
electronic configuration. [Given 20Ca40] [2]

Question 6 [10 marks]

(i) Formation of water is an exothermic, chemical reaction.

Warrant for this statement by justifying both the highlighted terms. [2]

(ii) The formula of a metal hydroxide of an element ‘W’ is W(OH)3. Without

identifying the element W, write the formula for its: [2]
(a) Nitrate
(b) Phosphite

(iii) State any one use for each of the following: [3]
(a) Bone charcoal
(b) Gas carbon
(c) Coke

(iv) Draw the orbit structure diagram to represent the formation of Magnesium
oxide and name the bond formed. [3]
[Given : 12Mg24 , 8O16].

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 Question 7 [10 marks]
(i) Match each example of a physical change with the correct physical property. [4]

Figure 8 Figure 9 Figure 10 Figure 11

A. Transpiration in B. A lit bulb C. Sugar dissolved D. Knitting a
leaves in water sweater
1. Change of shape
2. Solubility
3. Malleability
4. Change of state
5. Thermal conductivity
(ii) Balance the following word equations. [3]
(a) Ammonium nitrate breaks down at high temperatures to release
nitrogen, oxygen and water vapour.
(b) Zinc reacts with dilute hydrochloric acid to form zinc chloride and
releases hydrogen gas.
(c) Sodium hydroxide reacts with carbon dioxide to form sodium carbonate
and water.
(iii) The following table shows the electronic configuration of the atoms P, Q, R,
and S. Answer the questions that follow: [3]
Elements P Q R S
Electronic Configuration (2,8) (2,1) (2,7) (2,4)
(a) Which of the above element/s will form anions?
(b) Which of the above element/s will form cations?
(c) Which of the above element/s will form a covalent bond?

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