ICSE Class 6 Chemistry Sample Paper with Solutions Set 01

Question 1

Choose the correct answer out of the four available choices given under each question. [15]

1. Molecules of elements containing two or more atoms of different kinds which are chemically combined are called _______. [1 Mark]
(a) Atoms of compounds
(b) Molecules of compounds
(c) Molecules of mixtures
(d) Atoms of mixtures

Answer: (b) Molecules of compounds

Molecules of elements containing two or more atoms of different kinds which are chemically combined are called molecules of compounds.

Teacher's Note:
a) A compound is formed when two or more different elements combine chemically in a fixed proportion.
b) Students often confuse compounds with mixtures; remember that compounds involve chemical combination.

2. Which method is used for separation of small stone particles from wheat grains? [1 Mark]
(a) Winnowing
(b) Sieving
(c) Handpicking
(d) Filtration

Answer: (c) Handpicking

Handpicking method is used for separation of small stone particles from wheat grains.

Teacher's Note:
a) Handpicking is suitable when the quantity of impurities is small and the size, shape, or color of impurities is different from the main substance.
b) Do not confuse it with sieving, which is used when components differ in particle size.

3. Water freezes into ice at __________. [1 Mark]
(a) -4⁰C
(b) 0⁰C
(c) 5⁰C
(d) 10⁰C

Answer: (b) 0⁰C

Water freezes into ice at 0⁰C.

Teacher's Note:
a) The freezing point of pure water is the temperature at which liquid water turns into solid ice at standard atmospheric pressure.
b) Ensure proper unit notation (degrees Celsius) when writing temperatures in exams.

4. A ________is a calibrated glass tube with openings at both the ends used for measuring liquids. [1 Mark]
(a) Burette
(b) Glass jar
(c) Thistle funnel
(d) Pipette

Answer: (a) Burette

A burette is a calibrated glass tube with openings at both the ends used for measuring liquids.

Teacher's Note:
a) A burette is typically used in titration for precise delivery of variable volumes of liquid.
b) Distinguish it from a pipette, which measures a fixed volume of liquid.

5. The cover of air around the earth is called as [1 Mark]
(a) Atmosphere
(b) Air mixture
(c) Surrounding
(d) All of the above

Answer: (a) Atmosphere

The cover of air around the earth is called as Atmosphere.

Teacher's Note:
a) The atmosphere is held in place by the gravitational pull of the Earth.
b) Learn key scientific terms precisely; general terms like surrounding are too broad.

6. Which of the following is used to prepare face powder? [1 Mark]
(a) Talc
(b) Plaster of Paris
(c) Chalk
(d) Lime

Answer: (a) Talc

Talc is used to prepare face powder.

Teacher's Note:
a) Talc is a naturally occurring mineral composed of hydrated magnesium silicate.
b) It is soft and has moisture-absorbing properties, making it ideal for cosmetic powders.

7. Frost is the ___________ state of water. [1 Mark]
(a) Solid
(b) Liquid
(c) Gas
(d) Vapour

Answer: (a) Solid

Frost is the solid state of water.

Teacher's Note:
a) Frost forms when water vapor in the air comes into contact with a surface that is below freezing point and turns directly into ice crystals.
b) Recognize that frost is solid water, similar to ice and snow.

8. Sedimentation is used to separate a _________ mixture. [1 Mark]
(a) Solid-solid
(b) Liquid-solid
(c) Gas-solid
(d) Liquid-gas

Answer: (b) Liquid-solid

Sedimentation is used to separate a liquid-solid mixture.

Teacher's Note:
a) Sedimentation is the process in which heavier insoluble solid particles settle down at the bottom of a liquid.
b) This process is usually followed by decantation or filtration to obtain clear liquid.

9. The full form of DDT is [1 Mark]
(a) Diphenyl dibromo tetra ethane
(b) Dichloro-diphenyl-trichloro-ethane
(c) Dichloro-di-tri-methane
(d) All of the above

Answer: (b) Dichloro-diphenyl-trichloro-ethane

The full form of DDT is Dichloro-diphenyl-trichloro-ethane.

Teacher's Note:
a) DDT is a well-known synthetic insecticide with insecticidal properties.
b) Memorize scientific abbreviations and their complete chemical names accurately.

10. Urea is used as a [1 Mark]
(a) Antiseptic
(b) Fertilizer
(c) Antibiotic
(d) Insecticide

Answer: (b) Fertilizer

Urea is used as a Fertilizer.

Teacher's Note:
a) Urea is a nitrogen-rich organic compound widely used as a chemical fertilizer to enhance soil fertility.
b) Do not confuse fertilizers with pesticides or insecticides which protect crops from pests.

11. The name of John Dalton is associated with. [1 Mark]
(a) Nuclear theory
(b) Atomic theory
(c) Molecular theory
(d) Inorganic chemistry

Answer: (b) Atomic theory

The name of John Dalton is associated with Atomic theory.

Teacher's Note:
a) John Dalton proposed his atomic theory in 1808, stating that all matter is made of indivisible atoms.
b) Associate scientists with their primary discoveries for objective questions.

12. Non-metals are non-ductile and cannot be drawn into wires. [1 Mark]
(a) Metals
(b) Non-metals
(c) Metalloids
(d) Elements

Answer: (b) Non-metals

Non-metals are non-ductile and cannot be drawn into wires.

(Note: The question text repeats part of the property statement, referring to non-metals.)

Teacher's Note:
a) Ductility is a characteristic physical property of metals, whereas non-metals are brittle.
b) Read the options carefully to match the correct material classification.

13. Who discovered nitrogen gas? [1 Mark]
(a) Carl Scheele and Joseph Priestley
(b) Antoine Lavoisier and John Mathew
(c) Daniel Rutherford and John Mathew
(d) Daniel Rutherford and Antoine Lavoisier

Answer: (d) Daniel Rutherford and Antoine Lavoisier

Daniel Rutherford and Antoine Lavoisier discovered nitrogen gas.

Teacher's Note:
a) Nitrogen was independently discovered by Scottish physician Daniel Rutherford and French chemist Antoine Lavoisier.
b) Learn historical attributions of gas discoveries thoroughly.

14. Potable water should be free of ___________. [1 Mark]
(a) Bacteria
(b) Germs
(c) Impurities
(d) All of the above

Answer: (d) All of the above

Potable water should be free of bacteria, germs and impurities.

Teacher's Note:
a) Potable water refers to water that is safe to drink and fit for human consumption.
b) It must be free from harmful microorganisms and suspended chemical impurities.

15. Gases are least ________ as compared to solids and liquids. [1 Mark]
(a) Rigid
(b) Flexible
(c) Compressible
(d) Elastic

Answer: (a) Rigid

Gases are least rigid as compared to solids and liquids.

Teacher's Note:
a) Rigidity is the property of a substance to maintain its shape against external forces, which is highest in solids and least in gases.
b) Do not confuse rigidity with compressibility, where gases are the most compressible.

Question 2

(A) Define: [5 Marks]
1. Organic chemistry
2. Inorganic chemistry
3. Vaporisation
4. Condensation
5. Freezing

Answer:
1. Organic chemistry: Organic chemistry is a branch of chemistry which deals with the study of specific carbon compounds that consist of mainly carbon and hydrogen.
2. Inorganic chemistry: Inorganic chemistry is a branch of chemistry which deals with the study of innumerable elements and compounds including all metals and non-metals.
3. Vaporisation: Vaporisation is a process of conversion of a liquid into a vapour (or gas).
4. Condensation: Condensation is a process of conversion of vapour (or gas) into a liquid.
5. Freezing: Freezing is a process of conversion of a liquid into a solid.

Teacher's Note:
a) Definitions must include key scientific terms precisely as formulated in textbooks.
b) Ensure clear distinction between organic (carbon-based) and inorganic branches of chemistry.

(B) Fill in the blanks: [5 Marks]
1. ____________is the temperature at which a liquid starts boiling.
2. _________is generally added to impure water during the sedimentation process.
3. Dry hydrogen chloride gas is collected by the ________ of air.
4. Molecules in solid are ___________ together.
5. Plants take in _______ during respiration.

Answer:
1. 100⁰C (or Boiling point)
2. Alum
3. Upward displacement
4. Closely packed
5. Oxygen

Teacher's Note:
a) Alum acts as a coagulant during sedimentation to settle suspended impurities faster.
b) Gases like hydrogen chloride are collected by upward displacement of air due to being heavier than air.

Question 3

(A) State whether True or False: [5 Marks]
1. Xenon is an example of a noble gas.
2. Calcium is a non-metallic element.
3. Oxygen is a combustible gas.
4. Antiseptics are used for combating bacterial growth and initiating early recovery.
5. A flat bottom flask is used in gas preparation experiments where heating is required.

Answer:
1. True
2. False. Calcium is a metallic element.
3. False. Oxygen is a non-combustible gas (it supports combustion).
4. True
5. False. A round bottom flask is used in gas preparation experiments where heating is required.

Teacher's Note:
a) For False statements, students are expected to provide the correct corrected statement for full credit.
b) Remember that oxygen is a supporter of combustion, not a combustible gas itself.

(B) Write the techniques used for separating the following mixtures: [5 Marks]
1. Husk and wheat
2. Pebbles from pulses
3. Pure copper sulphate from impurities
4. Sugar from sugar solution
5. Tea leaves from tea

Answer:
1. Winnowing
2. Handpicking
3. Crystallisation and fractional crystallisation
4. Evaporation
5. Filtration (or using a filter)

Teacher's Note:
a) Match the separation technique to the physical properties of the components in the mixture.
b) Use exact technical terms like crystallisation and evaporation.

Question 4

(A) Match the elements with their correct valencies. [5 Marks]
Oxygen +1
Hydrogen −1
Carbon +3
Aluminium +4
Chlorine −2

Answer:

Teacher's Note:
a) Valency represents the combining capacity of an element.
b) Ensure correct signs (+ or -) are indicated alongside valency values where applicable.

(B) Label the marked parts with their respective charge. [5 Marks]

[Figure: Diagram of an atomic structure showing a central nucleus with protons and neutrons, surrounded by electron orbits with marked parts: 1 pointing to an electron on the outer orbit, 2 pointing to a neutron in the nucleus, and 3 pointing to a proton in the nucleus.]

Answer:
1 = Electrons with negative charge
2 = Neutrons with no or neutral charge
3 = Protons with positive charge

Teacher's Note:
a) Protons are positively charged subatomic particles located in the nucleus.
b) Electrons are negatively charged and revolve in orbits around the nucleus, while neutrons are neutral.

Question 5

(A) Classify the following as elements, compounds and mixtures: [5 Marks]
Air, Water, Oxygen, Hydrogen, Gun powder

Answer:

Teacher's Note:
a) Elements consist of only one kind of atoms, compounds consist of different elements chemically combined in fixed proportions, and mixtures consist of substances physically mixed.
b) Air and gun powder are classic examples of mixtures.

(B) Give the three methods of removal of impurities from water. [5 Marks]

Answer:
The three methods of removal of impurities from water are:
1. Sedimentation: During sedimentation, chemicals such as alum and lime are added to water which helps to coagulate the suspended impure particles which further settle in the sedimentation tank.
2. Filtration: During filtration, the water is passed through beds of sand and gravel which helps in removing suspended impurities and microorganisms.
3. Chlorination: During chlorination, chemicals such as chlorine, ozone, bleaching powder or potassium permanganate are added to kill the germs in the filtered water. This chlorinated water is then supplied to homes.

Teacher's Note:
a) Water purification involves sequential steps starting from sedimentation to remove heavy particles, filtration for fine suspended matter, and disinfection to kill germs.
b) Mentioning specific chemicals used in each process adds high value to answers.

Question 6

(A) Match the following [5 Marks]
A molecule of oxygen Na
Copper O₂
Nitrogen NH₃
Sodium N
A molecule of compound Cu

Answer:

Teacher's Note:
a) Elements are represented by standard chemical symbols derived from English or Latin names.
b) Compounds like ammonia (NH₃) consist of atoms of different elements chemically combined.

(B) Give the importance of chemistry in agriculture? [3 Marks]

Answer:
Several chemical compounds are used in agriculture. Some of these are:
1. Fertilisers help in improving the fertility of soil by supplying essential nutrients like nitrogen, phosphorus, and potassium.
2. Insecticides help in killing insects which infect and destroy crops.
3. Fungicides help in destroying fungi which cause plant diseases and destroy crops.
4. Herbicides help in killing unwanted weeds which grow along with crops and compete for nutrients.

Teacher's Note:
a) Chemistry plays a vital role in increasing agricultural yield and protecting crops.
b) Give specific agricultural chemicals (fertilizers, insecticides, fungicides, herbicides) with their functions to score full marks.

Question 7

(A) Give the difference between a pure substance and a mixture? [2 Marks]

Answer:

Teacher's Note:
a) Differentiation questions are best answered in a tabular format contrasting key properties.
b) Always provide appropriate examples to substantiate chemical differences.

(B) Enlist the composition of air [2 Marks]

Answer:

Teacher's Note:
a) Air is a homogeneous mixture of various gases, water vapor, and dust particles.
b) Mentioning percentages for major components (nitrogen and oxygen) is essential.

(C) Find the odd one out. [3 Marks]
1. Filtration, evaporation, loading, crystallisation.
2. Solution, compound, suspension, emulsion.
3. Soil, air, sea water, table-salt, milk

Answer:
1. Loading (Reason: Loading is a sedimentation technique used to speed up settling, whereas the others are methods of separation based on phase change or particle size).
2. Compound (Reason: A compound is a pure substance formed by chemical combination, whereas solution, suspension, and emulsion are types of mixtures).
3. Table-salt (Reason: Table-salt is a pure substance / compound, whereas soil, air, sea water, and milk are mixtures).

Teacher's Note:
a) Identify the common category among most options to isolate the odd one out.
b) Briefly stating the reason adds clarity and ensures full credit.

(D) Give the name of the scientist who [5 Marks]
1. Discovered oxygen
2. Discovered carbon dioxide
3. Discovered chlorine
4. Created the modern periodic table
5. Arranged elements in the increasing order of their atomic weights in the form of a table

Answer:
1. Joseph Priestley
2. De Lassone (or Joseph Black)
3. Carl Scheele
4. Henry Moseley
5. Dmitri Mendeleev

Teacher's Note:
a) History of chemistry questions require exact names of pioneering scientists.
b) Distinguish between Mendeleev (atomic weights / original periodic table) and Moseley (atomic numbers / modern periodic table).