SCIENCE: CLASS X - DAILY REVISION SYLLABUS FOR STUDENTS
SCIENCE: CLASS X - DAILY REVISION SYLLABUS FOR STUDENTS
CHAPTER 1: METALS AND NON-METALS
VERY SHORT ANSWER TYPE QUESTIONS [1 MARK]
1. A green layer is gradually formed on a copper plate left exposed to air for a week in a bathroom. What could this green substance be?
Answer. It is due to the formation of basic copper carbonate \( [\text{CuCO}_3.\text{Cu(OH)}_2] \).
2. A non-metal X exists in two different forms Y and Z. Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
Answer. ‘X’ is carbon, ‘Y’ is diamond as it is the hardest natural substance and ‘Z’ is graphite as it is a good conductor of electricity.
3. Metals generally occur in solid state. Name and write symbol of a metal that exists in liquid state at room temperature.
Answer. Mercury (Hg) exists in liquid state at room temperature.
4. Which of the following two metals will melt at body temperature (37 °C)? Gallium, Magnesium, Caesium, Aluminium
Answer. Gallium and Caesium.
5. From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal (a) which reacts with water only on boiling, and (b) another which does not react even with steam.
Answer. (a) Magnesium reacts with water only on boiling. (b) Copper does not react even with steam.
6. Which one of the following metals does not react with oxygen even at high temperatures? (a) Calcium (b) Gold (c) Sodium
Answer. (b) Gold does not react with oxygen even at high temperatures.
7. Name any one metal which reacts neither with cold water nor with hot water, but reacts with heated steam to produce hydrogen gas.
Answer. Iron; \( 3\text{Fe}(s) + 4\text{H}_2\text{O}(g) \rightarrow \text{Fe}_3\text{O}_4(s) + 4\text{H}_2(g) \)
8. Why does calcium float in water?
Answer. It is because hydrogen gas is formed which sticks to the surface of calcium, therefore it floats.
9. Name a non-metal which is lustrous and a metal which is non-lustrous.
Answer. Iodine is a non-metal which is lustrous, lead is a non-lustrous metal.
10. Which gas is liberated when a metal reacts with an acid? How will you test the presence of this gas?
Answer. Hydrogen gas is formed. Bring a burning matchstick near to it, \( \text{H}_2 \) will burn explosively with a ‘pop’ sound.
11. Name the metal which reacts with a very dilute \( \text{HNO}_3 \) to evolve hydrogen gas.
Answer. Magnesium.
12. Name two metals which are found in nature in the free state.
Answer. (i) Gold (ii) Silver.
13. What is the valency of silicon with atomic number 14?
Answer. Its valency is equal to 4.
14. What is the valency of phosphorus with atomic number 15?
Answer. Phosphorus has valency 3.
15. What is the valency of an element with atomic number 35?
Answer. Its valency is 1.
16. Arrange the following metals in the decreasing order of reactivity: Na, K, Cu, Ag.
Answer. \( \text{K} > \text{Na} > \text{Cu} > \text{Ag} \)
17. An element forms an oxide, \( \text{A}_2\text{O}_3 \) which is acidic in nature. Identify A as a metal or nonmetal.
Answer. ‘A’ is non-metal as non-metallic oxides are acidic in nature.
SHORT ANSWER TYPE QUESTIONS [I] [2 MARKS]
19. Write one example of each of (i) a metal which is so soft that, it can be cut with knife and a non-metal which is the hardest substance. (ii) a metal and a non-metal which exist as liquid at room temperature.
Answer. (i) Sodium, carbon (diamond). (ii) Mercury is liquid metal, bromine is liquid non-metal.
20. Mention the names of the metals for the following: (i) Two metals which are alloyed with iron to make stainless steel. (ii) Two metals which are used to make jewellery.
Answer. (i) Nickel and chromium. (ii) Gold and platinum.
21. Give reason for the following: (a) School bells are made up of metals. (b) Electric wires are made up of copper.
Answer. (a) It is because metals are sonorous, i.e., they produce sound when struck with a hard substance. (b) It is because copper is a good conductor of electricity.
22. Name the following: (a) A metal, which is preserved in kerosene. (b) A lustrous coloured non-metal. (c) A metal, which can melt while kept on palm. (d) A metal, which is a poor conductor of heat.
Answer. (a) Sodium. (b) Iodine. (c) Gallium. (d) Lead.
23. Explain why calcium metal after reacting with water starts floating on its surface. Write the chemical equation for the reaction. Name one more metal that starts floating after some time when immersed in water.
Answer. Calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
Equation: \( \text{Ca}(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2 + \text{H}_2(g) \)
Magnesium reacts with hot water and starts floating due to the bubbles of hydrogen gas sticking to its surface.
24. Give reason for the following: (a) Aluminium oxide is considered as an amphoteric oxide. (b) Ionic compounds conduct electricity in molten state.
Answer. (a) It is because it reacts with acids as well as bases to produce salts and water. ‘Al’ is less electropositive metal. So, it forms amphoteric oxide which can react with acid as well as base. (b) Ionic compounds can conduct electricity in molten state because ions become free to move in molten state.
25. Write two differences between calcination and roasting.
Answer.
| Calcination | Roasting |
|---|---|
| (i) It is carried out by heating ore in the absence of air. | (i) It is carried out by heating ore in the presence of air. |
| (ii) It converts carbonate ores into oxides. | (ii) It converts sulphide ores into oxides. |
26. The way, metals like sodium, magnesium and iron react with air and water is an indication of their relative positions in the ‘reactivity series’. Is this statement true? Justify your answer with examples.
Answer. Yes, sodium reacts explosively even with cold water, it is most reactive. Magnesium reacts with hot water, it is less reactive than Na. Iron reacts only with steam which shows it is least reactive among the three.
27. \( X + YSO_4 \rightarrow XSO_4 + Y \); \( Y + XSO_4 \rightarrow \text{No reaction} \). Out of the two elements, ‘X’ and ‘Y’, which is more reactive and why?
Answer. ‘X’ is more reactive than ‘Y’ because it displaces ‘Y’ from its salt solution.
28. What is an alloy? State the constituents of solder. Which property of solder makes it suitable for welding electrical wires?
Answer. Alloy is a homogeneous mixture of two or more metals. One of them can be a non-metal also. Solder consists of lead and tin. It has a low melting point which makes it suitable for welding electrical wires.
31. (a) Give two methods to prevent the rusting of iron. (b) Name the ores of the following metals: (i) mercury, and (ii) zinc.
Answer. (a) (i) Painting (ii) Galvanisation. (b) (i) Cinnabar (ii) Zinc Blende.
32. Write chemical equations that show aluminium oxide reacts with acid as well as base.
Answer.
\( \text{Al}_2\text{O}_3 + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2\text{O} \)
\( \text{Al}_2\text{O}_3 + 2\text{NaOH} \rightarrow 2\text{NaAlO}_2 + \text{H}_2\text{O} \)
SHORT ANSWER TYPE QUESTIONS [II] [3 MARKS]
34. State three reasons for the following facts (i) Sulphur is a non-metal (ii) Magnesium is a metal. One of the reasons must be supported with a chemical equation.
Answer.
Sulphur is a non-metal: (i) Poor conductor of heat and electricity. (ii) Neither malleable nor ductile. (iii) \( \text{S} + \text{O}_2 \rightarrow \text{SO}_2 \); \( \text{SO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_3 \) (Sulphurous acid). Sulphur dioxide is an acidic oxide.
Magnesium is a metal: (i) Good conductor of heat and electricity. (ii) Malleable and ductile. (iii) \( 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \); \( \text{MgO} + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2 \) (Magnesium hydroxide). Magnesium oxide is basic in nature.
35. What is cinnabar? How is metal extracted from cinnabar? Explain briefly.
Answer. Cinnabar is HgS. Mercury is obtained by roasting cinnabar. HgO formed is thermally unstable and gives mercury. Mercury can be purified by distillation.
\( 2\text{HgS}(s) + 3\text{O}_2(g) \rightarrow 2\text{HgO}(s) + 2\text{SO}_2(g) \)
\( 2\text{HgO}(s) \xrightarrow{\text{heat}} 2\text{Hg}(l) + \text{O}_2(g) \)
39. You are provided with magnesium ribbon and sulphur powder. Explain with the help of an activity that metal oxides are basic and non-metal oxides are acidic in nature.
Answer.
Aim: To test the nature of oxides formed by metals and non-metals.
Procedure:
1. Take magnesium ribbon and burn it in a flame. Collect the product (MgO) and dissolve it in warm water. Add red litmus paper. It turns blue, indicating it is basic.
2. Burn sulphur in a deflagrating spoon and dissolve the oxide formed (\(\text{SO}_2\)) in water. Dip blue litmus paper. It turns red, indicating it is acidic.
Equations:
\( 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \)
\( \text{MgO} + \text{H}_2\text{O} \rightarrow \text{Mg(OH)}_2 \) (Basic)
\( \text{S} + \text{O}_2 \rightarrow \text{SO}_2 \)
\( \text{SO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{SO}_3 \) (Acidic)
42. A metal ‘X’ acquires a green colour coating on its surface on exposure to air. (i) Identify the metal ‘X’ and name the process responsible for this change. (ii) Name and write chemical formula of the green coating formed on the metal. (iii) List two important methods to prevent the process.
Answer. (i) Metal is copper. Process is corrosion. (ii) Basic copper carbonate \( [\text{CuCO}_3.\text{Cu(OH)}_2] \). (iii) It should be coated with tin; It should be mixed with other metals to form alloys.
45. What is meant by ‘rusting’? With labelled diagrams, describe an activity to find out the conditions under which iron rusts.
Answer. The process in which iron reacts with oxygen in the presence of moisture to form a reddish brown coating of hydrated ferric oxide [Iron (III) oxide] \( \text{Fe}_2\text{O}_3.x\text{H}_2\text{O} \) is called rusting.
Activity:
(i) Take three boiling tubes A, B and C.
(ii) Tube A: Iron nails + Water (Air present).
(iii) Tube B: Iron nails + Boiled distilled water + Oil layer (Air excluded).
(iv) Tube C: Iron nails + Anhydrous Calcium Chloride (Moisture excluded).
Observation: Rusting occurs only in Tube A where both air and water are present.
CHAPTER 2: CARBON AND ITS COMPOUNDS
VERY SHORT ANSWER TYPE QUESTIONS [1 MARK]
1. Give the names of the following functional groups: (i) —OH (ii) —COOH
Answer. (i) Alcohol group (ii) Carboxylic acid group
2. What is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds?
Answer. —\( \text{CH}_2 \) —
3. Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene.
Answer. Ethanol (\( \text{CH}_3\text{CH}_2\text{OH} \)).
10. State two characteristic features of carbon which when put together give rise to large number of carbon compounds.
Answer. (i) Catenation (ii) Tetravalency of carbon.
SHORT ANSWER TYPE QUESTIONS [I] [2 MARKS]
27. (a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons. (b) Name the products formed when ethanol burns in air. (c) Why is the reaction between methane and chlorine considered a substitution reaction?
Answer.
(a) Add bromine water. Saturated hydrocarbons do not react (no colour change), whereas unsaturated hydrocarbons decolourise bromine water.
(b) \( \text{CO}_2 \) and \( \text{H}_2\text{O} \) with heat and light.
(c) Because ‘Cl’ atom substitutes ‘H’ atom of methane to form chloromethane and hydrogen chloride.
\( \text{CH}_4 + \text{Cl}_2 \xrightarrow{\text{Sunlight}} \text{CH}_3\text{Cl} + \text{HCl} \)
36. (a) What is meant by a functional group in an organic compound? (b) State one point of difference between soap and synthetic detergent.
Answer. (a) Functional group is an atom or group of atoms which determines the chemical properties of the compound. (b) Soaps do not work well with hard water, detergents work well with hard water.
41. Name the functional group of organic compounds that can be hydrogenated. With the help of suitable example explain the process of hydrogenation mentioning the conditions of the reaction.
Answer. Double bond (=) or Triple bond ($\equiv$) functional groups (alkenes/alkynes).
Hydrogenation is the addition of hydrogen to unsaturated hydrocarbons in the presence of catalysts like Nickel (Ni) to form saturated hydrocarbons.
Example: Vegetable oils (unsaturated) \( + \text{H}_2 \xrightarrow{\text{Ni, heat}} \) Vegetable ghee (saturated).
45. What is an ‘esterification’ reaction? Describe an activity to show esterification.
Answer. Esterification is the reaction between an acid (carboxylic acid) and an alcohol in the presence of conc. \( \text{H}_2\text{SO}_4 \) to form an ester (fruity smelling compound).
\( \text{CH}_3\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{CH}_3\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \)
Activity: Warm ethanol and ethanoic acid with a few drops of conc. sulphuric acid in a water bath. A pleasant fruity smell indicates the formation of an ester.
64. What is the difference between the chemical composition of soaps and detergents? State in brief the action of soaps in removing an oily spot from a shirt.
Answer. Soaps are sodium or potassium salts of long-chain fatty acids (\(-\text{COONa}\)). Detergents are sodium or potassium salts of sulphonic acids (\(-\text{SO}_3\text{Na}\)).
Cleansing Action: Soap molecules have a hydrophobic tail (hydrocarbon) which attaches to oil/dirt and a hydrophilic head (ionic) which attaches to water. They form structures called micelles trapping the oil in the center. When water is agitated, the oily dirt is lifted off the fabric.
CHAPTER 3: LIFE PROCESSES
1. What will happen to a plant if its xylem is removed?
Answer. Xylem transports water and dissolved minerals from roots to other parts. If removed, the water supply will stop, and the plant will die.
2. Where does digestion of fat take place in our body?
Answer. In the small intestine.
5. Mention the raw materials required for photosynthesis.
Answer. (i) Carbon Dioxide (\( \text{CO}_2 \)), (ii) Water (\( \text{H}_2\text{O} \)), (iii) Sunlight, (iv) Chlorophyll.
13. Name the intermediate and the end products of glucose breakdown in aerobic respiration.
Answer. Intermediate: Pyruvate. End products: \( \text{CO}_2 \) and \( \text{H}_2\text{O} \) + Energy.
35. (i) Write the balanced chemical equation for the process of photosynthesis.
Answer. \( 6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow{\text{Sunlight, Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{H}_2\text{O} + 6\text{O}_2 \)
58. (a) “The breathing cycle is rhythmic whereas exchange of gases is a continuous process”. Justify. (c) How opening and closing of stomata takes place?
Answer. (a) Breathing involves inhalation and exhalation controlled by the thoracic cavity rhythmically. Exchange of gases occurs continuously between blood and cells via diffusion. (c) Guard cells swell when water flows into them, opening the stomatal pore. They shrink when water moves out, closing the pore.
60. Explain the process of breakdown of glucose in a cell (ii) in the absence of oxygen.
Answer.
Step 1: Glucose (6-C) breaks down to Pyruvate (3-C) in cytoplasm (Glycolysis).
Step 2: In absence of oxygen (e.g., in yeast), Pyruvate converts to Ethanol + \( \text{CO}_2 \) + Energy (Fermentation). In muscle cells (lack of oxygen), Pyruvate converts to Lactic Acid + Energy.
CHAPTER 4: CONTROL AND COORDINATION
1. How is the spinal cord protected in the human body?
Answer. It is enclosed in a bony cage called the vertebral column.
4. Mention the function of adrenaline hormone.
Answer. It prepares the body for "fight or flight" situations by increasing heart rate, breathing rate, blood pressure, and diverting blood to muscles.
21. What is synapse? In a neuron cell how is an electrical impulse created and what is the role of synapse in this context?
Answer. A synapse is the gap between two neurons. An electrical impulse travels along the axon to the nerve ending, where it triggers the release of chemical neurotransmitters. These chemicals cross the synapse and start a similar electrical impulse in the dendrite of the next neuron.
61. What is meant by reflex-action? With the help of a labelled diagram trace the sequence of events which occur when we touch a hot object.
Answer. Reflex action is an unconscious, automatic, and involuntary response to a stimulus. Sequence (Reflex Arc): Receptor (Heat/Pain) \( \rightarrow \) Sensory Neuron \( \rightarrow \) Spinal Cord (Relay Neuron) \( \rightarrow \) Motor Neuron \( \rightarrow \) Effector (Muscle contracts).
CHAPTER 8: ELECTRICITY
19. State Ohm’s law. Write the necessary conditions for its validity.
Answer. Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference applied across its ends, provided physical conditions (like temperature) remain constant.
\( V \propto I \) or \( V = IR \).
24. An electric bulb of resistance \( 200\,\Omega \) draws a current of 1 Ampere. Calculate the power of the bulb, the potential difference at its ends and the energy in kWh consumed burning it for 5h.
Answer.
\( R = 200\,\Omega, I = 1\,\text{A} \)
Power \( P = I^2R = 1^2 \times 200 = 200\,\text{W} \)
Potential Difference \( V = IR = 1 \times 200 = 200\,\text{V} \)
Energy \( E = P \times t = 200\,\text{W} \times 5\,\text{h} = 1000\,\text{Wh} = 1\,\text{kWh} \)
33. Deduce the expression for the equivalent resistance of the parallel combination of three resistors \( R_1, R_2 \) and \( R_3 \).
Answer. In parallel, potential difference \( V \) is same. Current \( I \) splits.
\( I = I_1 + I_2 + I_3 \)
Using Ohm's law \( I = V/R \):
\( \frac{V}{R_p} = \frac{V}{R_1} + \frac{V}{R_2} + \frac{V}{R_3} \)
Dividing by \( V \):
\( \frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} \)
CHAPTER 9: LIGHT – REFLECTION AND REFRACTION
16. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the image formed?
Answer.
Given: \( u = -30\,\text{cm}, f = -15\,\text{cm}, h_o = 2\,\text{cm} \)
Mirror Formula: \( \frac{1}{f} = \frac{1}{v} + \frac{1}{u} \)
\( \frac{1}{-15} = \frac{1}{v} + \frac{1}{-30} \Rightarrow \frac{1}{v} = -\frac{1}{15} + \frac{1}{30} = \frac{-2+1}{30} = -\frac{1}{30} \)
\( v = -30\,\text{cm} \). (Screen placed at 30 cm in front of mirror).
Nature: Real and Inverted (since \( v \) is negative and mirror is concave).
Magnification \( m = -\frac{v}{u} = -\frac{-30}{-30} = -1 \).
Size \( h_i = m \times h_o = -1 \times 2 = -2\,\text{cm} \). (Same size as object).
22. The refractive index of glass is 1.50 and the speed of light in air is \( 3 \times 10^8\,\text{ms}^{-1} \). Calculate the speed of light in glass.
Answer.
\( n = \frac{c}{v} \Rightarrow v = \frac{c}{n} \)
\( v = \frac{3 \times 10^8}{1.50} = 2 \times 10^8\,\text{ms}^{-1} \)
36. (c) A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact. Calculate the lens power of this combination.
Answer.
\( f_1 = +25\,\text{cm} = +0.25\,\text{m} \Rightarrow P_1 = \frac{1}{0.25} = +4\,\text{D} \)
\( f_2 = -10\,\text{cm} = -0.10\,\text{m} \Rightarrow P_2 = \frac{1}{-0.10} = -10\,\text{D} \)
Power of combination \( P = P_1 + P_2 = +4 - 10 = -6\,\text{D} \).
CHAPTER 13: ACIDS, BASES AND SALTS
4. Write a balanced chemical equation for a neutralisation reaction.
Answer. \( \text{NaOH}(aq) + \text{HCl}(aq) \rightarrow \text{NaCl}(aq) + \text{H}_2\text{O}(l) \)
29. How is sodium hydrogencarbonate converted into washing soda?
Answer. Heating baking soda (\( \text{NaHCO}_3 \)) gives sodium carbonate.
\( 2\text{NaHCO}_3 \xrightarrow{\text{heat}} \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} + \text{CO}_2 \)
Recrystallisation of sodium carbonate gives washing soda:
\( \text{Na}_2\text{CO}_3 + 10\text{H}_2\text{O} \rightarrow \text{Na}_2\text{CO}_3 \cdot 10\text{H}_2\text{O} \)
49. What is Plaster of Paris chemically? How is it prepared?
Answer. Chemically: Calcium sulphate hemihydrate (\( \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} \)).
Preparation: Heating Gypsum at 373 K.
\( \text{CaSO}_4 \cdot 2\text{H}_2\text{O} \xrightarrow{373\,\text{K}} \text{CaSO}_4 \cdot \frac{1}{2}\text{H}_2\text{O} + 1\frac{1}{2}\text{H}_2\text{O} \)
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