(A) Fill in the blanks.
(i) The quantity of matter in an object is called its …………………….
(ii) In a ……………………… change the composition and the properties of the substance involved remain the same.
(iii) The substances are not combined chemically in a ……………………….
(iv) Oxygen reacts with non-metals to form ………………… oxides.
(v) ………………… is the naturally occurring hardest substance.
(B) Write ‘true’ or ‘false’ for the following statements:
(i) A chemical equation gives both qualitative and quantitative information about the reactants and products.
(ii) Non-metals like nitrogen, phosphorus and sulphur show variable valency.
(iii) Oxygen is the most important and the most abundant element found on the earth.
(iv) Evaporation increases with the increase in the humidity of air.
(v) Antimony is a metal.
(C) Choose the correct alternative from the options given below for the following statements.
(i) A chemical equation describes a chemical change in terms of
(a) Number of atoms
(b) Light and energy
(c) Symbols and formulae
(d) Colour
(ii) A metal that is bad conductor of heat and electricity is
(a) Copper
(b) Silver
(c) Lead
(d) Aluminium
(iii) The substance that cannot sublime is
(a) Iodine
(b) Ammonium sulphate
(c) Dry ice
(d) Camphor
(iv) The one which is not a mixture
(a) Fruit juice
(b) Bread
(c) Brass
(d) Distilled water
(v) Balancing of chemical equation is based on
(a) Law of conservation of mass
(b) Symbols and formulae
(c) Mass of reactants and products
(d) Valency of elements
(D) Match the statements in Column A, with those in Column B
| Column A | Column B |
| (i) Rust | (a) Basic oxide |
| (ii) Calcium oxide | (b) Yellow |
| (iii) Lead monoxide | (c) Carbonate |
| (iv) Pop sound | (d) Hydrated Iron (III) oxide |
| (v) Limestone | (e) Hydrogen |
(E) Statements given below are incorrect. Write correct statements.
(i) Smallest unit of compound is atom.
(ii) Oxygen supports combustion and is combustible.
(iii) Limewater is used as a chemical test for sulphur dioxide.
(iv) Lead is used in fireworks.
(v) Burning of coal in insufficient supply of air is produces carbon dioxide.
(F) Give one word for the following:
(i) The solid particles which remain on the filter paper after the filtration.
(ii) The process of change of liquid into solid.
(iii) Charged ions consisting of an atom or group of atoms of different elements.
(iv) A Nobel metal.
(v) Scientist who discovered oxygen.
(G) Define the following terms:
(i) Melting
(ii) Heterogeneous mixture
(iii) Periodic Table
(iv) Chemical reaction
(v) Rusting
(H) Find the odd one out.
(i) CO, NO2, SO2, CO2, O2
(ii) Magnesium, Nitrogen, Silver, Zinc, Mercury
(iii) Sugar solution, Salt solution, Mud solution, Tap-water
(iv) Rusting, Burning, Combustion, Melting
(v) Sodium, Juice, Butter, Ice-cream
A
(i) Mass
(ii) Physical
(iii) Mixture
(iv) Acidic
(v) Diamond
B.
(i) True
(ii) True
(iii) True
(iv) False
(v) False
C.
(i) (c)
(ii) (c)
(iii) (b)
(iv) (d)
(v) (a)
D.
(i) -(d)
(ii) -(a)
(iii) -(b)
(iv) -(e)
(v) -(c)
E.
(i) Smallest unit of a compound is molecule.
(ii) Oxygen supports combustion and is non-combustible.
(iii) Limewater is used as a chemical test for carbon dioxide.
(iv) Magnesium is used in fireworks.
(v) Burning of coal in insufficient supply of air is produces carbon monoxide.
F.
(i) Residue
(ii) Freezing
(iii) Radicals
(iv) Gold
(v) Priestley
(G)
(i) Melting is the process in which substance in solid state changes into liquid state at a particular temperature.
(ii) A mixture in which the components or constituents are not uniformly distributed throughout its volume and can be easily seen separately is called a heterogeneous mixture.
(iii) Periodic table is a tabular arrangement of elements in vertical columns and horizontal rows indicating the regular trends in the properties of elements.
(iv) Any change in matter which involves its transformation into one or more new substances is a chemical change also called as chemical reaction.
(v) Rusting is a slow oxidation process in which iron slowly reacts with oxygen of the air in presence of moisture and produces reddish brown substance, called rust.
(H)
(i) O2: O2 is not responsible for causing air pollution while all the other gases listed cause air pollution.
(ii) Nitrogen: Nitrogen is a non-metal while other examples are of metals.
(iii) Mud solution: Mud solution is a heterogeneous solution while other options are examples of a homogeneous mixture.
(iv) Melting: Melting is the process of conversion of a solid into liquid while other processes lead to formation of oxides.
(v) Sodium: Sodium is an element while others are examples of mixtures.
(i) Define matter and state the three main characteristics of the particles of matter.
(ii) How is an atom different from a molecule?
(iii) Differentiate between solids, liquids and gases.
(i) Matter is anything which has mass, occupies space and can be perceived by our senses.
The three main characteristics of matter are:
1. Particles of matter have space between them. This space is called as inter-particular space or intermolecular space.
2. Particles of matter are always in random motion.
3. Particles of matter attract each other.
(ii)
| Atom | Molecule |
| Smallest particle of an element which may or may not exist independently in nature but takes part in a chemical reaction | Smallest particle of a pure substance which exists independently and retains all the chemical and physical properties of that substance |
(iii)
|
| Solids | Liquids | Gases |
| 1. | In solids, molecules are closely packed and there are no intermolecular spacesbetween them. | In liquids, molecules are loosely packed and there are few intermolecular spaces between them. | In gases, molecules are very loosely packed and there are large intermolecular spaces between them. |
| 2. | In solids, molecules are strongly attracted towards each other and hence, they are dense. | In liquids, attractive forces between the molecules are lesser than solids. | In gases, molecules are weakly attracted towards each other. Hence, they are very less dense. |
| 3. | Solids occupy a definite volume and cannot be compressed. | Liquids have definite volume and can be compressed slightly. | Gases don’t have definite volume and can be compressed easily. |
| 4. | Solids have fixed shape and do not flow. | Liquids do not have fixed shape and take the shape of container. Liquids can flow easily. | Gases do not have any shape of their own and take the shape of the container they are put in. They can flow in all directions. |
| 5. | Molecules have very low kinetic energy. | Molecules have kinetic energy greater than solids. | Molecules have maximum kinetic energy. |
(i) Indicate whether the given changes are physical or chemical changes:
(a) Formation of dew
(b) Glowing of tube light
(c) Baking of cake
(d) Ringing of electric bell
(e) Ripening of fruit
(f) Clotting of blood
(g) Breaking of glass
(h) Condensation of water
(i) Burning of wood
(j) Smoking of cigarette
(ii) Define dissolution? State any two factors that affect the rate of dissolution? Discuss the process of dissolution of quick lime in water.
(i)
(a) Physical change
(b) Physical change
(c) Chemical change
(d) Physical change
(e) Chemical change
(f) Chemical change
(g) Physical change
(h) Physical change
(i) Chemical change
(j) Chemical change
(ii) The process in which a substance mixes thoroughly in another substance is known as dissolution.
The factors that affect dissolution are:
1. Temperature: More is the temperature, more is the dissolution.
2. Stirring: Greater the stirring, more is dissolution.
Dissolution of quicklime (CaO) in water
When small pieces of quicklime are added tothe beaker containing water, it is observed that water becomes very hot and a milky white solution is formed.
This is due to the fact that reaction between quicklime and water is an example of exothermic reaction.
(i) What is chromatography? On what principle is the method based and what are its advantages?
(ii) Name the process by which the components of mixture can be separated.
(a) Iron and sand
(b) Common salt and sea water
(c) Chaff and grain
(d) Sugar and water
(e) Water and mustard oil.
(i) The process of separating different dissolved constituents of a mixture by their absorption on an appropriate material is called chromatography.
The method is based on the difference in the rates of absorption of different components on the surface of a suitable adsorbent.
Advantages of chromatography:
1. It can be applied to separate a very small amount of a mixture.
2. The components of mixture do not get wasted during separation.
3. It is used to purify a large number of industrial products.
(ii)
(a) Iron and sand – Magnetic separation
(b) Common salt and sea water - Evaporation
(c) Alcohol and water – Fractional distillation
(d) Sawdust and water - Filtration
(e) Sand and iodine - Sublimation
(i) Discuss the relationship between the valency of elements and Periodic table.
(ii) What is atomicity? Give an example of each of the following:
(a) Monoatomic molecule
(b) Diatomic molecule
(c) Triatomic molecule
(d) Polyatomic molecule
(i) Valency is the combining capacity of an element or of a radical. Generally, valency of elements ranges from 0 to 4.
In a Periodic Table elements present in the same group have same valency and it also corresponds to the group number upto IV.
Example: Group IA has Lithium, sodium and potassium. They are all reactive metals with valency 1. Group IVA has carbon and silicon with valency 4.
Valency of elements present in Group V, VI and VII are 3, 2, 1 respectively. Group zero contains inert gases with zero combining capacity.
Thus, metals with same valency show similar properties and so do the non-metals.
(ii) Atomicity is defined as number of atoms present in a molecule of an element.
Monoatomic molecule – Helium (He)
Diatomic molecule – Hydrogen (H2)
Triatomic molecule – Ozone (O3)
Polyatomic molecule – Phosphorus (P4)
(i) Write word equations for the following reactions.
(a) CO + O2 → CO2
(b) AgBr → Ag + Br2
(c) FeCl2 + Cl2 → FeCl3
(d) Mg + O2 → MgO
(e) H2 + O2 → H2O
(ii) Write your observations for the following reactions:
(a) Sugar is heated
(b) Ammonium chloride is heated with sodium hydroxide.
(c) Hydrochloric acid is added to solid sodium carbonate.
(d) Potassium iodide is added to lead acetate solution
(e) Hydrogen chloride is heated with iron sulphide
(i)
(a) Carbon monoxide + Oxygen → Carbon dioxide
(b) Silver bromide → Silver + Bromine
(c) Ferrous chloride + Chlorine → Ferric chloride
(d) Magnesium + Oxygen → Magnesium oxide
(e) Hydrogen + Oxygen → Water
(ii)
(a) When sugar is heated it melts first and then gets charred into a black residue which is a new substance charcoal.
(b) When solid ammonium chloride is heated with sodium hydroxide solution, a gas with pungent smell i.e., ammonia is evolved.
(c) When dilute hydrochloric acid is added to solid sodium carbonate, a strong effervescence is observed indicating evolution of a gas.
(d) When potassium iodide solution is added to lead acetate solution, a yellow precipitate of lead iodide is produced.
(e) When dilute hydrochloric acid is heated with iron-sulphide, a gas hydrogen sulphide with rotten egg smell is evolved.
(i) What is corrosion and how can we prevent it?
(ii)
(a) How is oxygen prepared in the laboratory? Write the balanced chemical equation for the chemical reaction.
(b) Why is hydrogen peroxide preferred over potassium chlorate for the preparation of oxygen?
(c) What is the role of manganese dioxide in the preparation of oxygen?
(d) Why is oxygen collected by downward displacement of water?
(i) Corrosion is eating away and eventual destruction of metals when they come in contact of moist air.
The various methods used for prevention of corrosion are as follows:
(a) Painting: It is the most common method of preventing corrosion. The metals are coated with paint in this method.
(b) Galvanisation: In this method, iron is protected from rusting by coating it with a thin layer of non-corrosive metal like zinc.
(c) Electroplating: Iron and steel are protected from corrosion by coating them with a layer of tin or chromium metals which are resistant to corrosion.
(d) Tinning: In this process iron sheets are dipped in molten tin. Tin is corrosion resistant and non-toxic metal.
(ii)
(a) In the laboratory oxygen is prepared by the decomposition of hydrogen peroxide. The oxygen gas is collected by the downward displacement of water.
(b) Hydrogen peroxide and manganese dioxide is preferred for the preparation of oxygen gas because:
(c) Manganese dioxide acts as a catalyst and speeds up the rate of reaction.
(d) Oxygen is collected by downward displacement of water because it is only slightly soluble in water. Therefore, it can be collected over water without fear of excessive dilution. Secondly, being slightly heavier than air, oxygen cannot be collected over air.
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