CBSE Class class-10 Science — Very Short Answer Questions

(a) State two differences between the act of chewing food and salivation on sight of food. OR (b) State two differences between pollination and fertilization.

What is the function of diaphragm in human respiratory system? Where is it present in human body?

The given figure shows image formation by a lens. Analyse the figure and answer the following questions: (a) What is the type of lens used for image formation in the given ray diagram? (b) If the real image is formed at a distance of $30\mathrm{cm}$ from the lens and the size of image is twice the size of the object, then where was the object placed?

(a) What are amphoteric oxides? (b) Categorise the following based on their nature: $\mathrm{ZnO,Na_2O,CO_2}$

Draw a neat diagram to show germination of pollen on the female reproductive part of the flower. Name and label only the following parts: (a) The part that receives the pollen grain. (b) The structure that carries the male germ cell to reach the female germ cell.

Why the lungs always contain a residual volume of air?

(A) Observe the given figure and identify the labelled parts P, Q, R and S: [figure] OR (B) Which of the plant hormones are responsible for the following processes? (i) Promote cell division (ii) Inhibition of growth (iii) Detection of light (iv) Wilting of leaves

Given below is a diagrammatic representation of cross-section of a leaf: [figure] (i) Identify 'P' in the given diagram and write down its role in plants. (ii) Write down a balanced equation of process of photo-synthesis.

(A) (i) How does the change in curvature of the eye lens help us in the process of seeing nearby objects clearly? (ii) State the range of the power of accommodation of a normal human eye. OR (B) Draw a ray diagram to show the correction of eye defect of an old man who cannot see an object placed closer than $1\text{ m}$ from his eye, clearly.

How is a universal indicator obtained? How is the wide range of pH of solution tested by it?

(a) Define absolute refractive index of an optical medium. (b) Table: Material Medium / Refractive Index — A: 1.50, B: 1.46, C: 1.31, D: 1.77. Arrange these material mediums given in the table in increasing order of speed of light through them.

Briefly mention the steps in double-circulation through human heart.

(a) How is brain protected in our body? (b) A doctor finds in one of his patients that he is not maintaining a proper posture and balance of his body. State the region of brain and also the part of brain which is responsible for it.

Study the figure in which the path of a ray of light going from Medium 1 to Medium 2 is shown. (a) Out of the two Media - Medium 1 and Medium 2, in which is the speed of light more? (b) State reason of bending of the refracted ray away from the normal. (c) Express refractive index of Medium 2 with respect to Medium 1 in terms of speed of light in two media.

A light green coloured solution of sulphate salt of metal 'P' is taken in a beaker, a rod of another metal 'Q' is put in this solution as shown the following figures: Identify the metals 'P' and 'Q' and write its chemical equation for the reaction that occurs. State the conclusion of this reaction in terms of reactivity series of metals.

We do not clean natural ponds or lakes whereas an aquarium or a swimming pool needs to be cleaned regularly. Why?

(a) Give reasons: (i) The sky appears dark to passengers flying at very high altitude. (ii) 'Danger' signal lights are red in colour. OR (b) What is a rainbow? "We see a rainbow in the sky only after the rainfall." Why?

(a) "Proteins control the expression of various characters." Explain this statement by taking an example of "tallness" as a characteristic in plants. OR (b) Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of DNA of the species.

The values of absolute refractive indices of kerosene and water are 1.44 and 1.33 respectively. Compare the two media on the basis of their (a) optical density (b) mass density (c) relative speed of propagation of light. What do you infer on the basis of above comparisons?

(A) State two applications of Joule's heating in domestic electric circuit. OR (B) (a) Establish the relationship between the commercial unit of electric energy and the SI unit of electric energy. (b) Determine the total resistance of the parallel combination of three resistances of $2 \Omega$, $4 \Omega$ and $6 \Omega$.

(a) Why are the organisms of first trophic level important in any food chain? (b) Justify the following statement: 'The flow of energy in an ecosystem is unidirectional.'

(A) How is lymph formed ? State its important function. OR (B) (a) Identify 'X' in the figure of human nephron shown below. What role does it play in the process of urine formation ? (b) Why some substances are selectively reabsorbed from the initial filtrate of urine, as it flows along the tabular part of nephron ?

A crystalline substance of green colour 'X' emits gases of characteristic odour when heated over a flame. It first loses water and changes colour. On further heating, it decomposes and produces a solid compound Y. (a) Identify 'X' and 'Y'. (b) State the change in colour observed when 'X' is heated.

Give reasons : (a) The male reproductive organ responsible for formation of germ cells is located outside the abdominal cavity. (b) The roles of the glands, present along the path of the vas-deferens, are very significant.

What are magnetic field lines. List two important properties of magnetic field lines.

Explain with the help of a flow chart that in human beings father is responsible for the sex (male or female) of the child.

"Plants use a variety of techniques to get rid of waste material." Justify this statement giving any four ways.

(A) Show the formation of magnesium chloride by electron transfer. Write the name of the cation and anion present in the compound formed. (Atomic Number of $Mg = 12$, $Cl = 17$) OR (B) How is zinc extracted from its ore? Name the processes involved in the extraction and write chemical equations for the reactions that occur during these processes.

Define oxidation. Identify and name the substance oxidised in the following reaction: $CuO + H_2 → Cu + H_2O$

(A) Draw a ray diagram to show the refraction of a ray of light passing through an equilateral glass prism. Mark the angle through which the emergent ray bends from the direction of the incident ray and also name it. OR (B) Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.

An electric kettle is rated 230 V; 1000 W. Calculate the resistance of its heating element when in operation.

(a) List the possible sources of energy required in decomposition reactions. Illustrate any one with a suitable example. OR (b) What is observed when hydrated ferrous sulphate crystals are heated in a dry boiling tube? Give balanced chemical equation(s) of the reactions(s) that occur(s).

(a) Write the formula of the ions which (i) acids, and (ii) bases generate in water solutions. (b) Dry HCl gas does not change the colour of dry litmus paper. Why?

State the main function of veins in human circulatory system. Why do they not need thick walls?

(a) Explain how the proteins control the 'characteristics' in an organism with the help of an example of 'tallness' trait in pea plant. (b) Name the section of DNA that controls the 'characteristics' in an organism.

(a) A student has difficulty in reading his textbooks but can read the blackboard clearly while sitting in the last row. Name the defect of vision the student is suffering from. List two reasons due to which this defect arises. Write the nature of the lenses required to correct this defect. OR (b) Draw a ray diagram to show the path of a ray of light falling obliquely on one of the refracting faces of a triangular glass prism and mark the angle of deviation on it.

(a) Select from the following the members of same homologous series: [structures shown in the accompanying diagram] (b) What happens to (i) the melting point, and (ii) the solubility of compounds as the molecular mass of the compounds in a homologous series increases?

An electric kettle is rated $750\ \mathrm{W}$; $220\ \mathrm{V}$. Can this kettle be used in a circuit which has a fuse of current rating $3\ \mathrm{A}$? Give reason for your answer.

(a) Out of the two lenses, one concave and the other convex, state which one will diverge a parallel beam of light falling on it. Draw a ray diagram to show the principal focus of the lens. OR (b) A ray of light after refraction from a convex lens emerges parallel to its principal axis. (i) Draw a labelled ray diagram to show it. (ii) In this case, the incident ray before refraction from the lens passes through a point on its principal axis. Name the point.

(a) Write one function each of the following, in a seed: (i) Seed coat (ii) Cotyledon (iii) Radicle (iv) Plumule OR (b) Write the main steps to culture yeast in the laboratory.

Name the parts of hind-brain of the human brain. Which part of the hind-brain controls involuntary actions such as blood pressure and salivation?

(a) In common practice silver is recovered from silver nitrate solution by the use of copper metal. Name the type of reaction that takes place in this process and give the chemical equation of the reaction involved. (b) Name the method used for refining silver.

An object is placed at a distance of $60\ cm$ from a concave lens of focal length $30\ cm$. Use lens formula to find the position of the image formed in this case.

(a) Besides minimising the loss of blood, why is it essential to plug any leak in a blood vessel? Name the component of blood which helps in this process and state how this component perform this function. OR (b) (i) The transport system in plants is relatively slower than in animals. Give reasons. (ii) State the role of phloem in the transport of materials in plants.

Draw labelled diagrams to show different stages of budding in Hydra.

A student performs the following experiment in his school laboratory. List two observations to justify that in this experiment a chemical change has taken place.

"Excessive use of chemicals and pesticides in agriculture adversely effect the environment." Justify this statement.

(a) A wire of resistance R is cut into three equal parts. If these three parts are then joined in parallel, calculate the total resistance of the combination so formed. OR (b) Define electric power. When do we say that the power consumed in an electric circuit is 1 watt?

Some unicellular organisms such as Plasmodium and Leishmania differ in the manner in which they reproduce. Name and explain the reproductive process taking place in them.

The melting and boiling points of carbon compounds are generally low and they are largely non-conductors of electricity. State two conclusions based on these two properties.

(a) Copper powder is taken in a china dish and heated over a burner. Name the product formed and state its colour. Write the chemical equation for the reaction involved. OR (b) Write chemical equation for the chemical reaction which occurs when the aqueous solutions of barium chloride and sodium sulphate react together. Write the symbols of the ions present in the compound precipitated in the reaction.

An electric source can supply a charge of 500 coulomb. If the current drawn by a device is $25 \mathrm{mA}$, find the time in which the electric source will be discharged completely.

The heat produced at a point due to concentration of sunlight by a convex lens burns a paper. (a) Explain why it happens. (b) Name the term (in the context of the lens used) given to the point at which the paper starts burning. What does the bright spot formed on the paper represent?

(a) Sometimes while running, the athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration? OR (b) Write the other name given to lymph. State its two functions.

The survival of a species is promoted through creation of variations. Illustrate with an example.

Distinguish between a saturated and an unsaturated hydrocarbon by flame test. List the products of combustion reaction of a saturated hydrocarbon.

(a) 1 gram of solid sodium chloride was taken in a clean and dry test tube and concentrated sulphuric acid was added to it. (i) Name the gas evolved in the reaction. (ii) What will be observed when this gas is tested with (I) dry, and (II) wet blue litmus paper? Write your conclusion about the nature (acidic/basic) of this gas. OR (b) Some metals react with acids to produce salt and hydrogen gas. Illustrate it with an example. How will you test the presence of this gas?

Two wires A and B of same material, having same lengths and diameters $0.2 \mathrm{mm}$ and $0.3 \mathrm{mm}$ respectively, are connected one by one in a circuit. Which one of these two wires will offer more resistance to the flow of current in the circuit? Justify your answer.

A person suffering from presbyopia needs bifocal lens. If he needs two lens of power - 4.0 dioptre and + 2.0 dioptre, which one of these two lenses is for the correction of distant vision and what is its focal length?

(a) We need to water the soil in plants on a regular basis. But it ultimately reaches the leaves of the plant. Explain how this takes place. OR (b) Name the type of nutrition exhibited by Amoeba. Explain how food is taken in and digested by this organism.

When do we say that a particular person is suffering from hypermetropia? List two causes of this defect. Name the type of lens used to correct this defect.

When magnesium ribbon is burnt in air, an ash of white colour is produced. Write chemical equation for the reaction giving the chemical name of the ash produced. State the type of chemical reaction giving justification for your answer.

Where are auxins synthesized? How do they promote phototropism?

What are decomposers? List two consequences of their absence in an ecosystem.

(a) Draw a labelled diagram to show the pattern of magnetic field lines produced due to a current carrying straight conductor. Mark on it the direction of current in the conductor and the direction of magnetic field lines. OR (b) Name the device used to magnetise a piece of magnetic material. Draw a labelled diagram to show the arrangement used for the magnetisation of a cylinder made of soft iron.

(a) List any two pairs of visible contrasting characters of garden pea plants used by Mendel for his experiments stating the dominant and recessive characters in each pair. OR (b) In human beings, the probability of getting a male or a female child is $50\%$. Explain with the help of a flow diagram only.

(a) "No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statement giving a balanced chemical equation for the reaction. OR (b) Giving one example of each, differentiate between a displacement reaction and a double displacement reaction.

Name the term used for the materials which cannot be broken down by biological processes. Give two ways by which they harm various components of an ecosystem.

(a) State two laws of refraction of light. OR (b) Define the term absolute refractive index of a medium. A ray of light enters from vacuum to glass of absolute refractive index 1.5. Find the speed of light in glass. The speed of light in vacuum is $3 \times 10^{8} \mathrm{~m / s}$.

"Stability of DNA in a species is ensured during sexual reproduction." Justify the statement.

Photosynthesis takes place in the leaves and the food prepared by it reaches other parts of the plants. Name the process involved and explain it.

Use Ohm's law to determine the potential difference across the $3 \Omega$ resistor in the circuit shown in the following diagram when key is closed:

Name the type of chemical reaction in which calcium oxide reacts with water. Justify your answer by giving balanced chemical equation for the chemical reaction.

State one role of each of the following in human digestive system: (i) Hydrochloric acid (ii) Villi (iii) Anal Sphincter (iv) Lipase

(A) How is the movement of leaves of a sensitive plant different from the downward movement of the roots? OR (B) There is a hormone which regulates carbohydrate, protein and fat metabolism in our body. Name the hormone and the gland which secretes it. Why is it important for us to have iodised salt in our diet?

(A) Show how you would connect three resistors each of resistance $6\Omega$, so that the combination has a resistance of $9\Omega$. Also justify your answer. OR (B) In the given circuit calculate the power consumed in watts in the resistor of $2\Omega$ :

(i) Two magnetic field lines do not intersect each other. Why ? (ii) How is a uniform magnetic field in a given region represented ? Draw a diagram in support of your answer.

An object is placed at a distance of $10\mathrm{cm}$ from a convex mirror of focal length $15\mathrm{cm}$. Find the position of the image formed by the mirror.

State whether the given chemical reaction is a redox reaction or not. Justify your answer. $MnO_2 + 4HCl \longrightarrow MnCl_2 + 2H_2O + Cl_2$

(a) List two differences between the movement of leaves of a sensitive plant and the movement of a shoot towards light. OR (b) What happens at synapse between two neurons? State briefly.

Give the name of the enzyme present in the fluid in our mouth cavity. State the gland which produces it. What would happen to the digestion process if this gland stops secreting this enzyme?

Let the resistance of an electrical device remain constant, while the potential difference across its two ends decreases to one fourth of its initial value. What change will occur in the current through it? State the law which helps us in solving the above stated question.

State the rule to determine the direction of a (a) magnetic field produced around a straight conductor carrying current and (b) force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it.

(a) Which one of the two media is denser w.r.t. other medium? Justify your answer (based on a ray entering from medium A to B). (b) If the speed of light in medium A is $v_a$ and in medium B is $v_b$, what is the refractive index of B with respect to A. OR (a) A ray of light starting from diamond is incident on the interface separating diamond and water. Draw a labelled ray diagram to show the refraction of light in this case. (b) Absolute refractive indices of diamond and water are 2.42 and 1.33 respectively. Find the value of refractive index of water w.r.t. diamond.

(a) On heating $X'$ at $373\mathrm{K}$, it loses water molecules and becomes $Y'$. $Y'$ is a substance which doctors use for supporting fractured bones in the right position. (i) Identify $X'$ and $Y'$. (ii) How can $X'$ be reobtained from $Y'$? OR (b) Two solutions M and N give Red and Blue colour respectively with a universal indicator. (i) In which solution will the hydrogen ion concentration be more? Justify your answer. (ii) If both M and N solutions are mixed and the resultant mixture is tested with a universal indicator, it turns green. What is the nature of the salt formed? Justify your answer.

(a) List the events in proper sequence that take place during the process of photosynthesis. OR (b) Explain in brief two ways by which leaves of a plant help in excretion.

In the process of digestion of food in human beings, two protein-digesting enzymes are secreted. Name the enzymes along with the glands that secrete them.

Observe the following diagram showing an image formation in an eye : (a) Identify the defect of vision shown in the figure. (b) List its two causes and suggest a suitable corrective lens to overcome this defect.

Write the name and function of parts (i) and (ii) in the diagram of a neuron given below.

In the following food chain, if 50 J of energy was available to the hawk, how much energy would have been present at the first and third tropic levels? Justify your answer. Grass $\longrightarrow$ Grasshopper $\longrightarrow$ Frog $\longrightarrow$ Snake $\longrightarrow$ Hawk

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.

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

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

(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

(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) 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 ?

(a) Why is it important to prevent oxygenated and deoxygenated blood from mixing in birds and mammals? (b) Which animals can tolerate some mixing of the oxygenated and deoxygenated blood streams? On what factor does the body temperature of these animals depend?

(a) What is observed when aqueous solutions of potassium iodide and lead nitrate are mixed together? Name the type of reaction and write the chemical equation for the reaction that occurs. OR (b) When copper powder is heated in a watch glass, a black substance is formed. (i) Why is this black substance formed? Name it. (ii) How can this black substance be reversed to its original form?

V-I graph for two conducting wires A and B are as shown. If both wires are of the same length and same diameter, which of the two is made of a material of high resistivity? Give reasons to justify your answer.

(a) When and where does a rainbow appear in the sky? Draw a labelled ray diagram to show its formation. OR (b) What is scattering of light? Why does the clear sky appear blue?