Question 1 (A) Choose the correct alternative
(i) Alkaline earth metals have valency 2. This means that their position in the modern periodic table is in _______.
- (A) Group 2
- (B) Group 16
- (C) Period 2
- (D) d-block
Answer: (A) Group 2
(ii) The reaction in which ions in the reactants are exchanged to form a precipitate is called as _______ reaction.
- (A) Combination
- (B) Decomposition
- (C) Displacement
- (D) Double Displacement
Answer: (D) Double Displacement
(iii) _______ is used to make a solenoid type coil in an electric bulb.
- (A) Nichrome
- (B) Copper
- (C) Tungsten
- (D) Aluminium
Answer: (C) Tungsten
(iv) Light changes its direction when going from one transparent medium to another transparent medium. This process is called _______.
- (A) Reflection
- (B) Dispersion
- (C) Scattering
- (D) Refraction
Answer: (D) Refraction
(v) CaO + H2O → Ca(OH)2 + Heat is an example of _______ reaction.
- (A) Exothermic
- (B) Electrolysis
- (C) Decomposition
- (D) Endothermic
Answer: (A) Exothermic
Question 1 (B) Answer the following questions
(i) State whether true or false: A redox reaction takes place during cellular respiration.
Answer: True.
(ii) Find the odd one out: Loudspeaker, microphone, electric motor, magnet.
Answer: Magnet. (Others are devices that convert energy using electromagnetism; a magnet is a static material/component).
(iii) What is the reason for twinkling of stars?
Answer: The twinkling of stars is due to the atmospheric refraction of starlight. As the density of the atmosphere changes continuously, the refractive index changes, causing the position and brightness of the star to fluctuate.
(iv) Match the columns: Simple microscope
Answer: Simple microscope — (c) used for watch repair.
(v) Name the behaviour of water between its temperature from \(0^{\circ}C\) to \(4^{\circ}C\).
Answer: Anomalous behaviour of water (Anomalous expansion).
Question 2 (A) Give scientific reasons (any two)
(i) While going from left to right within a period, the size of atom decreases.
Reason: While going from left to right in a period, the atomic number increases, meaning the positive charge on the nucleus increases. However, the electrons are added to the same outermost shell. The increased nuclear attraction pulls the electrons closer to the nucleus, thereby decreasing the size of the atom.
(ii) For electric power transmission, copper or aluminium wire is used.
Reason: Copper and aluminium are very good conductors of electricity with low resistivity. They minimize the loss of energy in the form of heat during transmission. Additionally, they are ductile and relatively abundant (especially Aluminium), making them suitable for wires.
(iii) In some countries, ethanol is used as an additive to increase the efficiency of petrol.
Reason: Ethanol is a clean-burning fuel. When mixed with petrol, it provides oxygen that helps the fuel burn more completely, reducing harmful emissions like carbon monoxide. It also reduces dependence on fossil fuels.
Question 2 (B) Answer the following (any three)
(i) Name and state the principle used to measure the specific heat capacity of a substance.
Answer:
Name: Principle of Heat Exchange.
Statement: If a system of two objects is isolated from the environment, heat energy lost by the hot object is equal to heat energy gained by the cold object.
Name: Principle of Heat Exchange.
Statement: If a system of two objects is isolated from the environment, heat energy lost by the hot object is equal to heat energy gained by the cold object.
(ii) What is done to prevent rusting of iron door of your house?
Answer: The iron door is painted. The layer of paint prevents the direct contact of iron with the moisture and oxygen in the air, thereby preventing rusting. Alternatively, processes like galvanization could be used before manufacturing.
(iii) Distinguish between mass and weight.
Mass: It is the amount of matter present in the object. It is a scalar quantity and remains constant everywhere.
Weight: It is the gravitational force acting on the object. It is a vector quantity and changes from place to place.
Weight: It is the gravitational force acting on the object. It is a vector quantity and changes from place to place.
(iv) The 'rocket' is a type of fire cracker used in Diwali. (a) Name the launcher. (b) Name the law on which its working is based.
(a) Launcher: A bottle or a hollow pipe is used as a support/launcher.
(b) Law: Newton's Third Law of Motion (Every action has an equal and opposite reaction).
(b) Law: Newton's Third Law of Motion (Every action has an equal and opposite reaction).
(v) What is meant by decomposition reaction? Write the chemical reaction of decomposition of sugar on heating.
Definition: The chemical reaction in which two or more products are formed from a single reactant is called a decomposition reaction.
Reaction: $$C_{12}H_{22}O_{11} \xrightarrow{\Delta} 12C + 11H_2O$$ (Sugar decomposes into Carbon and Water vapor).
Reaction: $$C_{12}H_{22}O_{11} \xrightarrow{\Delta} 12C + 11H_2O$$ (Sugar decomposes into Carbon and Water vapor).
Question 3. Answer the following (any five)
(i) An iron ball of mass 3 kg is released from a height of 125 m and falls freely to the ground. Assuming that the value of g is 10 m/s², calculate : (a) Time taken by the ball to reach the ground. (b) Velocity of the ball on reaching the ground.
Given:
Mass ($m$) = 3 kg
Distance ($s$) = 125 m
Initial velocity ($u$) = 0 (released freely)
Gravity ($g$) = 10 m/s²
(a) Time taken ($t$):
Using Newton's second equation of motion:
$$s = ut + \frac{1}{2}gt^2$$ $$125 = 0 \times t + \frac{1}{2} \times 10 \times t^2$$ $$125 = 5t^2$$ $$t^2 = \frac{125}{5} = 25$$ $$t = 5 \text{ seconds}$$
(b) Velocity ($v$):
Using Newton's first equation of motion:
$$v = u + gt$$ $$v = 0 + 10 \times 5$$ $$v = 50 \text{ m/s}$$
Mass ($m$) = 3 kg
Distance ($s$) = 125 m
Initial velocity ($u$) = 0 (released freely)
Gravity ($g$) = 10 m/s²
(a) Time taken ($t$):
Using Newton's second equation of motion:
$$s = ut + \frac{1}{2}gt^2$$ $$125 = 0 \times t + \frac{1}{2} \times 10 \times t^2$$ $$125 = 5t^2$$ $$t^2 = \frac{125}{5} = 25$$ $$t = 5 \text{ seconds}$$
(b) Velocity ($v$):
Using Newton's first equation of motion:
$$v = u + gt$$ $$v = 0 + 10 \times 5$$ $$v = 50 \text{ m/s}$$
(ii) Write the name and symbol of the element from the description: (a) The most electronegative atom. (b) The atom having smallest atomic mass. (c) The noble gas with the smallest atomic radius.
(a) Fluorine (F)
(b) Hydrogen (H)
(c) Helium (He)
(b) Hydrogen (H)
(c) Helium (He)
(iii) (a) What happens when copper reacts with concentrated nitric acid? What is the colour of the gas released during the reaction? (b) Write its balanced chemical equation. (c) Write the names of reactants and products.
(a) When copper reacts with concentrated nitric acid, reddish-brown fumes of nitrogen dioxide gas are released.
(b) Equation: $$Cu + 4HNO_3 (conc.) \rightarrow Cu(NO_3)_2 + 2NO_2 \uparrow + 2H_2O$$ (c) Reactants: Copper, Nitric Acid. Products: Copper Nitrate, Nitrogen Dioxide, Water.
(b) Equation: $$Cu + 4HNO_3 (conc.) \rightarrow Cu(NO_3)_2 + 2NO_2 \uparrow + 2H_2O$$ (c) Reactants: Copper, Nitric Acid. Products: Copper Nitrate, Nitrogen Dioxide, Water.
(iv) Name the following diagrams and explain the concept behind them: [Fleming's Left and Right Hand Rules Diagrams]
(a) Fleming's Left-Hand Rule: Used for Electric Motors. It states that if the thumb, index finger, and middle finger of the left hand are stretched perpendicular to each other, and if the index finger points in the direction of the magnetic field and the middle finger in the direction of the current, then the thumb points in the direction of the force on the conductor.
(b) Fleming's Right-Hand Rule: Used for Electric Generators (Induction). It states that if the thumb, index finger, and middle finger of the right hand are stretched perpendicular to each other, with the thumb showing the direction of motion of the conductor and the index finger the direction of the magnetic field, then the middle finger shows the direction of the induced current.
(b) Fleming's Right-Hand Rule: Used for Electric Generators (Induction). It states that if the thumb, index finger, and middle finger of the right hand are stretched perpendicular to each other, with the thumb showing the direction of motion of the conductor and the index finger the direction of the magnetic field, then the middle finger shows the direction of the induced current.
(v) Answer the following with respect to the 'Formation of Rainbow': (a) Draw a neat diagram. (b) Name any two natural processes involved. (c) What does a small droplet of water act as?
(a) Diagram: [Student should draw a water droplet showing sunlight entering, refracting, dispersing into colors, internally reflecting, and refracting out].
(b) Processes: Refraction, Dispersion, and Total Internal Reflection.
(c) A small droplet of water acts as a small Prism.
(b) Processes: Refraction, Dispersion, and Total Internal Reflection.(c) A small droplet of water acts as a small Prism.
(vi) Name the following: (a) The two metals which can be cut with knife. (b) A sound is produced when certain metals are struck. Name this property. (c) The non-metallic substance which is a good conductor of electricity.
(a) Sodium (Na) and Potassium (K).
(b) Sonority.
(c) Graphite (Allotrope of Carbon).
(b) Sonority.
(c) Graphite (Allotrope of Carbon).
(vii) Answer the following questions with the help of the given diagram (Electroplating): (a) Name the process. (b) How does this process take place? (c) Give two examples in which this process is used.
(a) Process: Electroplating.
(b) Working: When electricity is passed through the solution, silver ions ($Ag^+$) from the anode (Silver plate) dissolve into the electrolyte. An equivalent amount of silver ions from the solution get deposited on the cathode (Aluminium spoon).
(c) Examples: Gold plating on imitation jewelry, Silver plating on cutlery, Zinc plating on iron (galvanization) to prevent rust.
(b) Working: When electricity is passed through the solution, silver ions ($Ag^+$) from the anode (Silver plate) dissolve into the electrolyte. An equivalent amount of silver ions from the solution get deposited on the cathode (Aluminium spoon).
(c) Examples: Gold plating on imitation jewelry, Silver plating on cutlery, Zinc plating on iron (galvanization) to prevent rust.
(viii) Complete the following table:
| Type of satellite | Function of the satellite | Indian satellite series & launch vehicle |
|---|---|---|
| (a) Navigation Satellite | Fix the location of any place on the earth's surface | IRNSS Launcher: PSLV |
| (b) Weather satellite | Study and prediction of weather | INSAT / GSAT Launcher: GSLV |
| (c) Earth Observation Satellite | Management of natural resources | IRS Launcher: PSLV |
Question 4. Answer any one of the following
(i) (a) Draw a neat labelled diagram of human eye. (b) What is the minimum distance of distinct vision for a normal human eye? (c) Name the capacity of the eye lens to change its focal length as per need. (d) Name the defect of eye vision in which the focussing power of eye lens decreases with age.
(a) Diagram: [Student should draw the human eye, labelling Cornea, Iris, Pupil, Crystalline Lens, Ciliary Muscles, Retina, and Optic Nerve].
(b) Distance: 25 cm.
(c) Capacity: Power of Accommodation.
(d) Defect: Presbyopia.
(b) Distance: 25 cm.(c) Capacity: Power of Accommodation.
(d) Defect: Presbyopia.
(ii) Atomic number of chlorine is 17. (a) Write the electronic configuration of chlorine. (b) What is the number of electrons in the valence shell of chlorine? (c) Write the molecular formula of chlorine. (d) Name the type of bond in the formation of chlorine molecule. (e) Draw the electron dot structure of a chlorine molecule.
(a) Electronic Configuration: 2, 8, 7.
(b) Valence electrons: 7.
(c) Molecular Formula: Cl2.
(d) Bond Type: Covalent Bond (Single Covalent Bond).
(e) Electron Dot Structure:
Each Chlorine atom contributes 1 electron to share a pair.
$$: \ddot{Cl} \cdot \cdot \ddot{Cl} : \rightarrow : \ddot{Cl} - \ddot{Cl} :$$
(b) Valence electrons: 7.
(c) Molecular Formula: Cl2.
(d) Bond Type: Covalent Bond (Single Covalent Bond).
(e) Electron Dot Structure:
Each Chlorine atom contributes 1 electron to share a pair.
$$: \ddot{Cl} \cdot \cdot \ddot{Cl} : \rightarrow : \ddot{Cl} - \ddot{Cl} :$$
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