CBSE Class 10 Science 2023 Question Paper

When Sodium bicarbonate reacts with dilute hydrochloric acid, the gas evolved is :

When aqueous solutions of potassium iodide and lead nitrate are mixed, an insoluble substance separates out. The chemical equation for the reaction involved is :

A metal ribbon 'X' burns in oxygen with a dazzling white flame forming a white ash 'Y'. The correct description of X, Y and the type of reaction is :

Acid present in tomato is :

Sodium hydroxide is termed an alkali while Ferric hydroxide is not because :

The name of the salt used to remove permanent hardness of water is :

The electron dot structure of chlorine molecule is :

Observe the following diagram and identify the process and its significance from the following options :

Opening and closing of stomata is due to :

A cross between pea plant with white flowers (vv) and pea plant with violet flowers (VV) resulted in $F_2$ progeny in which ratio of violet (VV) and white (vv) flowers will be :

In plants the role of cytokinin is :

The number of chromosomes in parents and offsprings of a particular species undergoing sexual reproduction remain constant due to :

Two LED bulbs of $12W$ and $6W$ are connected in series. If the current through $12W$ bulb is $0.06A$ the current through $6W$ bulb will be :

The correct pattern of magnetic field lines of the field produced by a current carrying circular loop is :

The resistance of a resistor is reduced to half of its initial value. If other parameters of the electrical circuit remain unaltered, the amount of heat produced in the resistor will become :

An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is :

Assertion (A) : Reaction of Quicklime with water is an exothermic reaction. Reason (R) : Quicklime reacts vigorously with water releasing a large amount of heat.

Assertion (A) : In humans, if gene (B) is responsible for black eyes and gene (b) is responsible for brown eyes, then the colour of eyes of the progeny having gene combination Bb, bb or BB will be black only. Reason (R) : The black colour of the eyes is a dominant trait.

Assertion (A) : The inner walls of the small intestine have finger like projections called villi which are rich in blood. Reason (R) : These villi have a large surface area to help the small intestine in completing the digestion of food.

Assertion (A) : A current carrying straight conductor experiences a force when placed perpendicular to the direction of magnetic field. Reason (R) : The net charge on a current carrying conductor is always zero.

(A) A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution. (i) Write the name of the compound formed and its colour. (ii) Write a balanced chemical equation for the reaction involved. OR (B) The industrial process used for the manufacture of caustic soda involves electrolysis of an aqueous solution of compound 'X'. In this process, two gases 'Y' and 'Z' are liberated. 'Y' is liberated at cathode and 'Z', which is liberated at anode, on treatment with dry slaked lime forms a compound 'B'. Name X, Y, Z and B.

(A) Name the part of brain which is responsible for the following actions: (i) Maintaining posture and balance (ii) Beating of heart (iii) Thinking (iv) Blood pressure OR (B) Where are auxins synthesized in a plant ? Which organ of the plant shows : (i) Positive phototropism (ii) Negative geotropism (iii) Positive hydrotropism

Write one specific function each of the following organs in relation with excretion in human beings : (i) Renal Artery (ii) Urethra (iii) Glomerulus (iv) Tubular part of nephron

Two green plants are kept separately in oxygen free containers, one in the dark and other in sunlight. It was observed that plant kept in dark could not survive longer. Give reason for this observation.

(A) Observe the following diagram and answer the questions following it : (i) Identify the defect of vision shown. (ii) List its two causes. (iii) Name the type of lens used for the correction of this defect. OR (B) The colour of clear sky from the earth appears blue but from the space it appears black. Why ?

Use of several pesticides which results in excessive accumulation of pesticides in rivers or ponds, is a matter of deep concern. Justify this statement.

(i) While electrolysing water before passing the current some drops of an acid are added. Why ? Name the gases liberated at cathode and anode. Write the relationship between the volume of gas collected at anode and the volume of gas collected at cathode. (ii) What is observed when silver chloride is exposed to sunlight ? Give the type of reaction involved.

(i) Suggest a safe procedure of diluting a strong concentrated acid. (ii) Name the salt formed when sulphuric acid is added to sodium hydroxide and write its pH. (iii) Dry HCl gas does not change the colour of dry blue litmus paper. Why ?

(A) (i) How does Paramecium obtain its food ? (ii) List the role of each of the following in our digestive system : (a) Hydrochloric acid (b) Trypsin (c) Muscular walls of stomach (d) Salivary amylase OR (B) (i) What is double circulation? (ii) Why is the separation of the right side and the left side of the heart useful? How does it help birds and mammals?

(A) Define the following terms in the context of a diverging mirror: (i) Principal focus (ii) Focal length Draw a labelled ray diagram to illustrate your answer. OR (B) An object of height $10 cm$ is placed $25 cm$ away from the optical centre of a converging lens of focal length $15 cm$. Calculate the image-distance and height of the image formed.

The power of a lens is $+4D$. Find the focal length of this lens. An object is placed at a distance of $50 cm$ from the optical centre of this lens. State the nature and magnification of the image formed by the lens and also draw a ray diagram to justify your answer.

(A) (i) Why is an alternating current (A.C.) considered to be advantageous over direct current (D.C.) for the long distance transmission of electric power? (ii) How is the type of current used in household supply different from the one given by a battery of dry cells? (iii) How does an electric fuse prevent the electric circuit and the appliances from a possible damage due to short circuiting or overloading. OR (B) For the current carrying solenoid as shown, draw magnetic field lines and give reason to explain that out of the three points A, B and C, at which point the field strength is maximum and at which point it is minimum?

Write one difference between biodegradable and non-biodegradable wastes. List two impacts of each type of the accumulated waste on environment if not disposed off properly.

(A) (i) Draw the structure of the following compounds : (a) Butanoic acid (b) Chloropentane (ii) How are structure (i) and structure (ii) given below related to one another ? Give reason to justify your answer. Draw one more possible structure for above case. (iii) Differentiate between saturated and unsaturated carbon compounds on the basis of their general formula. OR (B) (i) What happens when a small piece of sodium is dropped in ethanol ? Write the equation for this reaction. (ii) Why is glacial acetic acid called so ? (iii) What happens when ethanol is heated at $443 K$ in the presence of conc. $H_2SO_4$ ? Write the role of conc. $H_2SO_4$ in this case. (iv) Write an equation showing saponification.

(i) Name and explain the two modes of asexual reproduction observed in hydra. (ii) What is vegetative propagation ? List two advantages of using this technique.

(i) How is electric current related to the potential difference across the terminals of a conductor ? Draw a labelled circuit diagram to verify this relationship. (ii) Why should an ammeter have low resistance ? (iii) Two V - I graphs A and B for series and parallel combinations of two resistors are as shown. Giving reason state which graph shows (a) series, (b) parallel combination of the resistors.

The melting points and boiling points of some ionic compounds are given below : | Compound | Melting Point (K) | Boiling Point (K) | | :--- | :--- | :--- | | NaCl | 1074 | 1686 | | LiCl | 887 | 1600 | | CaCl2 | 1045 | 1900 | | CaO | 2850 | 3120 | | MgCl2 | 981 | 1685 | These compounds are termed ionic because they are formed by the transfer of electrons from a metal to a non-metal. The electron transfer in such compounds is controlled by the electronic configuration of the elements involved. Every element tends to attain a completely filled valence shell of its nearest noble gas or a stable octet. (i) Show the electron transfer in the formation of magnesium chloride. (1 mark) (ii) List two properties of ionic compounds other than their high melting and boiling points. (1 mark) (iii) (A) While forming an ionic compound say sodium chloride how does sodium atom attain its stable configuration ? (2 marks) OR (iii) (B) Give reasons : (i) Why do ionic compounds in the solid state not conduct electricity ? (ii) What happens at the cathode when electricity is passed through an aqueous solution of sodium chloride ? (2 marks)

The most obvious outcome of the reproductive process is the generation of individuals of similar design, but in sexual reproduction they may not be exactly alike. The resemblances as well as differences are marked. The rules of heredity determine the process by which traits and characteristics are reliably inherited. Many experiments have been done to study the rules of inheritance. (i) Why an offspring of human being is not a true copy of his parents in sexual reproduction ? (1 mark) (ii) While performing experiments on inheritance in plants, what is the difference between $F_1$ and $F_2$ generation ? (1 mark) (iii) (A) Why do we say that variations are useful for the survival of a species over time ? (2 marks) OR (iii) (B) Study Mendel's cross between two plants with a pair of contrasting characters: $RRYY \times rryy$ (Round Yellow x Wrinkled Green). He observed 4 types of combinations in $F_2$ generation. Which of these were new combinations ? Why do new features which are not present in the parents, appear in $F_2$ generation ? (2 marks)

The ability of a medium to refract light is expressed in terms of its optical density. Optical density has a definite connotation. It is not the same as mass density. On comparing two media, the one with the large refractive index is optically denser medium than the other. The other medium with a lower refractive index is optically rarer. Also the speed of light through a given medium is inversely proportional to its optical density. (i) Determine the speed of light in diamond if the refractive index of diamond with respect to vacuum is 2.42. Speed of light in vacuum is $3 \times 10^8 m/s$. (1 mark) (ii) Refractive indices of glass, water and carbon disulphide are 1.5, 1.33 and 1.62 respectively. If a ray of light is incident in these media at the same angle (say $\theta$), then write the increasing order of the angle of refraction in these media. (1 mark) (iii) (A) The speed of light in glass is $2 \times 10^8 m/s$ and in water is $2.25 \times 10^8 m/s$. (a) Which one of the two is optically denser and why? (b) A ray of light is incident normally at the water-glass interface when it enters a thick glass container filled with water. What will happen to the path of the ray after entering the glass? Give reason. (2 marks) OR (iii) (B) The absolute refractive indices of water and glass are $4/3$ and $3/2$ respectively. If the speed of light in glass is $2 \times 10^8 m/s$, find the speed of light in (i) vacuum and (ii) water. (2 marks)