Allied solutions simplified middle school chemistry class 6 Solutions for Chapter 2 elements compounds and mixtures

Q1) Classify the substances into pure and impure substances in the form of a chart or tabulation.

Q2) Differentiate between the terms – elements, compounds & mixtures.

Q3) The important physical properties of substances are colour, odour, nature, density & solubility in water. Name –

(a) Two coloured gases (with their colours)

(b) A gas with a pungent, choking odour which is lighter than air.

(c) A poisonous gas almost as heavy as air.

Q4) Complete the statement – an element is a pure substance made up of (identical/different) atoms.

Q5) Draw a labelled diagram of an atom including its nucleus, orbits & their contents.

Q6) Elements are classified into – metals – nonmetals – metalloids – noble gases. State which of A, B, C, D is a –

1. Metallic element

2. Non-metallic element

3. Metalloid

4. Noble gas

A: is non-malleable, non-ductile & a poor conductor of electricity

B: has lustre, is malleable and ductile & a good conductor of heat

C: is unreactive and inert and present in traces in air

D: shows properties of both metals and nonmetals

Q7) An atom of an element is denoted by a ‘symbol’. Explain the meaning of the term “symbol”

State a reason for representing the following elements by their symbols.

(a) Hydrogen by ‘H’

(b) Helium by ‘He’

(c) Copper by ‘Cu’

Q8) Match the metallic elements – with their correct symbols.

Metallic elements –

(a) Potassium (b) Sodium (c) Calcium (d) Magnesium (e) Zinc (f) Aluminium (g) Iron (h) Lead (i) Copper (j) Mercury (k) Silver (l) Platinum (m) Gold

Symbols – (1) Ca (2) Zn (3) Pb (4) Hg (5) Cu (6) Au (7) K (8) Fe (9) Al (10) Na (11) Mg (12) Pt (13) Ag

Q9) Match the non-metallic elements – with their correct symbols.

Non- Metallic elements –

(a) Carbon (b) Chlorine (c) Oxygen (d) Phosphorus (e) Hydrogen (f) Nitrogen (g) Iodine (h) Bromine (i)Fluorine (j) Silicon (k) Sulphur

Symbols – (1) O (2) I (3) Si (4) C (5) Cl (6) P (7) F (8) H (9) S (10) Br (11) N

Q10) Match the noble gases – with their correct symbols.

Noble gases –

(a) Helium (b) Neon (c) Argon (d) Krypton (e) Xenon (f) Radon

Symbols – (1) Ar (2) Xe (3) Rn (4) He (5) Kr (6) Ne

Q11) Give a reason why elements are tabulated in a table called ‘periodic table’.

Q12) Give the names and symbols of the first twenty elements of the periodic table. Differentiate them into metals, non-metals, metalloids and noble gases.

Q13) Explain the term – molecules. Give three examples of atoms of the same element forming a molecule. State the atomicity of the same.

Q14) Give one example of

(a) A triatomic molecule

(b) A polyatomic molecule

Q15) Explain the term compounds. Give the example of a compound containing

(a) Hydrogen and oxygen

(b) Carbon and oxygen

(c) Nitrogen and oxygen

(d) Calcium and oxygen

Q16) State two characteristics of water which prove that it is a – compound.

Q17) Explain the term ‘chemical formula’. State what a chemical formula denotes.

Q18) Give the symbols and the number of atoms of each element present in

(a) Sodium chloride (b) Water (c) Carbon dioxide (d) Zinc chloride

Q19) For writing a chemical formula – ‘symbols’ and combining capacity of an element with hydrogen i.e. ‘valency’ should be known. Explain the term – combining capacity of an element i.e. valency

Q20) State what are radicals. Give the names of the radicals –

1. H_2O
2. OH
3. CO_2
4. CO_3

Q21) Match the symbols of metallic elements – with their correct combining power or capacity.

(a) K

(b) Zn

(c) Al

(d) Na

(e) Ca

Combining power or capacity – A: 3, B: 2, C: 1. (positive valencies)

Q22) Match the symbols of non-metallic elements with their correct combining power or capacity.

(a) O (b) S (c) Cl

Combining power or capacity – A: 3, B: 2, C: 1. (negative valencies)

Q23) Match the symbols of – radicals – with their correct combining power or capacity (valency).

(a) OH (b) SO_4 (c) NO_3 (d) CO_3

Combining power or capacity – A: 3, B: 2, C: 1. (negative valencies)

Q24) Write the formula of the compound formed – given “symbols and combining power or capacity (valency) if each element in the compound.

(a) K^{1+}Cl^{1-}

(b) Na^{1+}Cl^{1-}

(c) Ca^{2+}NO_3^{1-}

Q25) Match the formulas of the following – gases – with their correct names:

(a) H_2 (b) N_2 (c) O_2 (d) Cl_2 (e) HCl (f) NH_3 (g) CO (h) CO_2 (i) SO_2 (j) NO (k) NO_2

(1) Ammonia (2) Nitrogen dioxide (3) Oxygen (4) Hydrogen (5) Nitrogen (6) Chlorine (7) Carbon monoxide (8) sulphur dioxide (9) nitrogen monoxide (10) Carbon dioxide (11) hydrogen chloride

Q26) Match the formulas of the following – acids – with their correct names

Acids: (a) HCl (b) HNO_3 (c) H_2SO_4 (d) H_2CO_3

Names: (1) Carbonic acid (2) Sulphuric acid (3) Hydrochloric acid (4) Nitric acid

Q27) Match the formulas of the following – bases – with their correct names

Bases: (a) NaOH (b) KOH (c) Ca\left(OH\right)_2 (d) Zn\left(OH\right)_2

Names: (1) Potassium hydroxide (2) Zinc hydroxide (3) Aluminium hydroxide (4) Calcium hydroxide (5) Sodium hydroxide

Q28) Complete the statements with the correct words.

(a) Acid’s – are chemicals whivh are _____ in taste and derived from plants and _____.

(b) Bases – are chemicals which are hydroxide (or oxides) of _____ eg. sodium hydroxide.

(c) Salts – are chemicals formed on reaction of a base with an _____ giving salt and water.

Q29) In the chemical word equation – Zinc + Sulphuric acid → Zinc sulphate + Hydrogen

(a) State the reactants and products of the above reaction. What does the arrow indicate?

(b) The molecular equation is Zn\ +\ H_2SO_4\ →\ ZnSO_4\ +\ H_2\ \left[g\right]. State what [[g]] represents.

Q1) Explain the term mixtures. Give an example of mixtures of –

(a) Two elements

(b) Two compounds

(c) Elements and compounds

Q2) Differentiate between homogeneous and heterogeneous mixtures with suitable examples.

Q3) With reference to the mixture of iron and sulphur, state the main characteristics of mixture.

Q4) Tabulate a comparative chart – to differentiate between elements, compounds and mixtures. Differentiate them with reference to

(a) The term

(b) Existence

(c) Properties

(d) Separation of components

Q5) State the principle involved in separation of solid-solid mixtures by –

(a) Sieving

(b) Magnetic separation

(c) Sublimation

Q6) State the principle involved in separation of solid-liquid mixtures by –

(a) Sedimentation and decantation

(b) Filtration

(c)Evaporation

Q7) Explain the term ‘sieving’. State the structure of a sieve and explain the separation of different sized particles by sieving.

Q8) State what is meant by magnetic separation of two mixtures’. Explain how iron particles can be separated from sulphur particles.

Q9) Give a reason why sublimable and non-sublimable substances can be separated easily but two sublimable substances cannot.

Q10) Explain the technique for separating – insoluble solid particles in a solid-liquid mixture.

Q11) Differentiate between the terms sedimentation and decantation with a suitable experimental technique.

Q12) Explain how a solid component is separated in a soluble solid-liquid mixture.

Q13) Draw a neat labelled diagram for separation of the following mixtures.

(a) Coarse sand from fine sand

(b) A magnetic particle from a non-magnetic particle

(c) Naphthalene from sodium chloride

(d) Chalk and water using filter paper

(e) Sand and water without using a filter paper

(f) Common salt from a solution of common salt and water.

Q14) State the technique involved in separating the following:

(a) Iodine crystals and potassium chloride

(b) Iron and chalk powder

(c) Potassium chloride from an aqueous solution of potassium chloride

(d) Rice powder from soil particles

(e) Iron filings from pieces of copper wire

(f) Large diamonds from very small diamonds

Q1) Complete the statements given below by filling in the blank with the correct word/s

1. An element is a pure substance which cannot be broken down by physical or ______ methods.

2. The basic unit of an element is an ______.

3. Atom contains ________, with positively charged ________.

4. Element _______ has the symbol derived from its Latin name ‘argentum’.

5. From the elements – He, Br, Pt and O; the element which is metallic is ___, an inert element is ____, forms a triatomic molecule is O, is liquid at room temperature.

6. From the elements nitrogen, chlorine, bromine, the element present in the atmosphere is nitrogen.

Q2) Match the statements in List I – 1 to 10 with their correct answers in List II – A to J.

Q3) Select the correct answer from the choice in brackets.

1. The symbol of – mercury [[Mg/Hg/Ag]]

2. The type of element-phosphorus [[metallic/non-metallic/noble gas]]

3. The type of molecule – bromine [[monoatomic/diatomic/triatomic]]

4. A compound [[nitrogen/ozone/zinc chloride]]

5. The unreactive non-metallic element [[chlorine/argon/sulphur]]

6. The negatively charged particle in an atom [[protons/neutrons/electrons]]

7. The element which is malleable [[sulphur/carbon/iron]]

8. An impure substance [[element/mixture/compound]]

9. An element which is a poor conductor of heat [[copper/carbon/aluminium]]

10. A group of atoms of elements [[ion/radical/combining power]]

Q4) Match the compounds in List I – 1 to 20 with their correct formulas from in List II – A to T

List I – 1. Hydrochloric acid 2. Potassium Hydroxide 3. Sulphuric acid 4. Zinc hydroxide 5. Sodium chloride 6. Nitric acid 7. Calcium hydroxide 8. Sodium hydroxide 9. Copper sulphate 10. Potassium chloride 11. Calcium carbonate 12. Magnesium sulphide 13. Zinc sulphate 14. Aluminium hydroxide 15. Sodium carbonate 16. Zinc sulphide 17. Magnesium oxide 18. Zinc oxide 19. Ammonium chloride

List II – A. NaCl B. NaOH C. KCl D. Ca\left(OH\right)_2 E. CaS F. CuSO_4 G. CaCO_3 H. NH_4Cl I. HCl J. ZnO K. HNO_3 L. H_2CO_3 M. MgS N. MgO O. KOH P. ZnSO_4 Q. Na_2CO_3 R. H_2SO_4 S. Al\left(OH\right)_3 T. Zn\left(OH\right)_2

Q1) Match the statements in List I with the correct answer in List II

Q2) State whether the following statements are true or false. If false write – the correct statement.

1. Components in a mixture are present in a definite proportion.

2. Mixture have no definite set of properties

3. Components in a mixture can be separated by physical and chemical methods.

4. Sodium chloride and water is an example of a mixture of compounds

5. Heterogeneous mixtures have different composition and properties throughout the mixture

Q3) Name the following:

1. A black non-metallic component of the mixture gunpowder.

2. A physical method of separating iron from an iron-sulphur mixture.

3. The component of the soluble solid-liquid mixture which is lost to the atmosphere on heating.

4. The coomponent of naphthalene-sodium chloride mixture which remains in the evaporating dish when heated together, covered with a funnel.

5. A mixture of two immiscible liquids.

Q4) Give reasons for the following:

1. Naphthalene and camphor cannot be separated by sublimation.
2. Sodium chloride cannot be separated out from its aqueous solution by filtration.
3. Two varieties of wheat flour cannot be separated by sieving.
4. Sulphur and charcoal powder cannot be separated by magnetic suspension.
5. Both components of a soluble solid-liquid mixture cannot be recovered by evaporation.