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Answer: c Archaeopteryx is a connecting link- between the reptiles and birds. It appears like a bird, but has other features which are present in reptiles, e.
For palaeontological studies a scientist will gather the evidences from a study of homology b study of analogy c fossils d All of these. Answer: d Study of homologous and analogous organs indicates the origin and modification in organisms and study of fossils indicates the age and features of an organism.
In evolutionary terms, we have more in common with [NCERT] a a Chinese school boy b a chimpanzee c a spider d a bacterium. Answer: a Chinese school boy because both of us belong to the same species, i. Homo sapiens. Aditya was observing some organisms in lab and tried to compare them. The presence of which organs will confirm to him that they share evolutionary history?
Answer: c Homologous organs are present in organisms who share evolutionary history. However, these organs perform different functions in different organisms.
New species may be formed if I. DNA undergoes significant changes in germ cells. Answer: a New species may be formed if the DNA changes are severe enough, such as a change in the number of chromosome. This leads to new variations. Which of the following statements is not true with respect to variation? Answer: a All variations in a species do not have equal chances of survival. Some of the variations may be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits.
Such, a newborn cell dies soon. Select the statement that describes characteristics of genes. Answer: b Genes are stretches of DNA found on chromosomes of a cell.
A gene contains information for making proteins in a cell. A specific gene is located on a particular chromosome in individuals of a given species. If a round, green seeded pea plant RRyy is crossed with wrinkled, yellow seeded pea plant rrYY , the seeds produced in F1 � generation will be [NCERT Exemplar] a round and yellow b round and green c wrinkled and green d wrinkled and yellow.
Answer: a The cross between RRyy and rrYY seeds will produce RrYy round and yellow seeds in F1-generation, because round and yellow are the dominant traits. From the list given below, select the character, which can be acquired but not inherited. Answer: c Acquired traits develop in response to the environment. The size of the body is an acquired trait because it can vary based on the availability of less or more food.
The other three colour of eye and skin and nature of hair are characters inherited from the parents. According to the evolutionary theory, formation of a new species is generally due to [NCERT Exemplar] a sudden creation by nature.
Answer: b Accumulation of variations over several generations forms new species. Genetic drift accumulates different changes in sub-populations of a species. Also, natural selection may also operate differendy in the different geographic locations. Eventually, different groups of new species will be formed. Select the incorrect statement. Answer: b The weight reduction due to starvation will not change the DNA of the germ cells, because low weight is not a trait that is genetically controlled or inherited.
Also, low weight parents may have heavy weight progeny. In human males all the chromosomes are paired perfectly except one. Answer: c In human males, one pair called the sex chromosomes are unpaired.
Here, one is a normal-sized X-chromosome while other is a short Y-chromosome. Women have a perfect pair of sex chromosomes, both called X. Rajneesh was studying the fossils of two different types, fossil A was found in upper layer of Earth and B in deeper layers. What can be predicted regarding the age of these fossils? Answer: a Since, fossil A was found in upper layer of earth, it suggests that the organism has become extinct recently.
Fossil B found in deeper layer must have become extinct long time ago and deposition of other layers occurred over it during this period. A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers.
The progeny all bore violet flowers, but almost half of them were short. Hold a highly polished steel spoon curved inwards close to your face and move it slowly away from your face.
What will you observe? Answer: b The inner curved surface of a highly polished steel spoon acts as a concave mirror. When the spoon is at a small distance from the face such that, the object lies between pole and focus of concave mirror, so an enlarged and erect image of your face will be observed but as the spoon is slowly moved away from the face, the image becomes smaller and appears inverted.
Which one of the following materials cannot be used to make a lens? No matter how far you stand from a mirror, your image appears erect. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
An object AB is placed in front of a convex lens at its centre of curvature as shown in figure below. Four students traced the path of light ray after refraction through the lens. Which one of them is correct? Answer: d When the object is placed at centre of curvature 2Fx of convex lens, the same sized image is formed at 2F2. The image formed is real and inverted.
A spherical mirror and a thin spherical lens have each of a focal length cm. The mirror and lens are likely to be [NCERT] a both concave b both convex c mirror is concave and lens is convex d mirror is convex and lens is concave.
Answer: a The focal length is taken as negative for both concave mirror and concave lens. Which of the following can make a parallel beam of light when light from a point source is incident on it? Under which of the following conditions, a concave mirror can form an image larger than the actual object? Answer: c A concave mirror can form an image enlarged, real and inverted than the actual object, beyond centre of curvature C when object is placed between the focus F and centre of curvature.
A light ray enters from medium A to medium Bas shown in the figure. Answer: a Since, light rays in the medium B goes towards normal. So, it has greater refractive index and lesser velocity of light w. So, refractive index of medium B w. Figure shows a ray of light as it travels from medium A to medium B. Refractive index of the medium B relative to medium A is.
Beams of light are incident through the holes A and B and emerge out of box through the holes C � and D respectively, as Box shown in the figure. Which of the following could be inside the box?
Answer: a Here, the emergent rays are parallel to the direction of the incident ray. Therefore, a rectangular glass slab could be inside the box as the extent of bending of light ray at the opposite parallel faces AB air-glass interface and CD glass-air interface of the rectangular glass slab are equal and opposite.
This is why the ray emerges parallel to the incident ray. A beam of light is incident through the holes on side A and emerges out of the holes on the other face of the box as shown in the figure. Answer: d Since, in the figure all the parallel rays converge at a point. So, inside the box there must be a convex lens.
Which of the following statement is true? Magnification produced by a rear view mirror fitted in vehicles [NCERT Exemplar] a is less than one b is more than one c is equal to one d can be more than or less than one depending upon the position of the object in front of it. Answer: a The convex mirror forms virtual, erect and diminished image of the object and rear view mirror also form same type of image.
Therefore, magnification m produced by a rear view mirror fitted in vehicles is less than one, i. Rays from the Sun converge at a point 15 cm in front of a concave mirror. Where should an object be placed, so that size of its image is equal to the size of the object? Answer: b The rays from the Sun, i.
Therefore, focal length if of concave mirror is 15 cm. Answer: b In a rectangular glass slab, the emergent rays are parallel to the direction of the incident ray, because the lateral deviation of bending of the ray of light at the opposite parallel faces air-glass interface and glass-air interface of the rectangular glass slab are equal and opposite. This is why the ray emerges are parallel to the incident ray. You are given water, mustard oil, glycerine and kerosene.
In which of these media, a ray of light incident obliquely at same angle would bend the most? Answer: d The given material having their refractive index as kerosene is 1. Thus, glycerine is most optically denser and hence have the largest refractive index. Therefore, ray of light bend most in glycerine. How many images will be observed by him? Where should an object be placed in front of a convex lens to get a real image of the size of the object?
Answer: b To set the real image of the size of the object, it should be placed at twice the focal length of a convex lens. Which of the following lenses would you prefer to use while reading small letters found in dictionary?
Answer: c Convex lens is used as magnifying glass. For better performance its focal length should be small. The human eye can focus objects at different distances by adjusting the focal length of eye lens.
Answer: b Accommodation is the ability of eye lens to focus both near and distant objects by adjusting its focal length. The change in focal length of eye lens is caused by action of [NCERT] a pupil b retina c ciliary muscles d iris.
Answer: c Ciliary muscles contract and extend in order to change the lens shape for focussing image ayretina. The least distance of distinct vision for a young adult with normal vision is about [NCERT] a 25 m b 2. Answer: c The minimum distance at which an object can be seen most distinctly without any strain is 25 cm. At noon the Sun appears white as [NCERT Exemplar] a light is least scattered b all the colours of the white light are scattered away c blue colour is scattered the most d red colour is scattered the most.
Answer: a At noon, the Sun appears white because the light from the Sun is directly over head and travel relatively shorter distance. The Sun appears white as only a little of the blue and violet colours are scattered. A person cannot see distinctly objects kept beyond 2 m. Which of the following phenomena of light are involved in the formation of a rainbow? Answer: c A rainbow is caused by dispersion, refraction and internal reflection of sunlight by tiny water droplets, present in the atmosphere and always formed in a direction opposite to that of the Sun.
The water droplets act like small prisms. They refract and disperse the incident sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop. A narrow beam of white light is incident on the prism as shown in figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?
Answer: b In ii case, after dispersion, the third colour from the top corresponds to colour of the sky, i. A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Answer: a The student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book because he is suffering from hypermetropia or far sightedness. He can see distant objects clearly but cannot see nearby objects distinctly.
In the following diagram, the path of a ray of light passing through a glass prism is shown below. Answer: d Angle of incidence is the angle made by the incident ray with the normal to the first surface of prism, which is shown by angle Y. Angle of emergence is the angle made by the emergent ray with the normal to the surface when it comes out from the prism after refraction, which is shown by angle Q. Angle of deviation is the angle between the incident ray and the emergent ray, which is shown by angle P.
To determine the equivalent resistance of two resistors when connected in series, a student arranged the circuit components as shown in the diagram. But he did not succeed to achieve the objective. Answer: c Because positive terminal of ammeter must be connected with positive terminal of cell and negative terminal of an ammeter must be connected to negative terminal of a cell.
For the given circuit, name the components which are connected in parallel. Answer: b The components R 1 , R 2 and V are connected in parallel combination. Because terminals of the resistance and voltmeter are connected together. A student arranges the following circuit to get equivalent resistance of a series combination of two resistors R 1 and R 2.
Which one of the following statements will be true for this circuit [CCE ] a It gives incorrect reading for current I as well as potential difference V b It gives correct reading for current I but incorrect reading for potential difference V c It gives correct reading for potential difference V but incorrect reading for current I d It gives correct reading for both I and V.
Answer: b The voltmeter should be connected across the components of and R 2 to give correct reading for potential difference. An ammeter has 20 divisions between 0 mark and 2A mark on its scale.
The least count of ammeter is a 0. A student finds that there are 20 divisions between zero mark and 1V mark of a voltmeter. The least count of voltmeter is a 0. The current flowing through a resistor connected in an electric circuit and the potential difference applied across its ends are shown in figure alongside. Answer: b In a circuit, ammeter should be connected in series, while voltmeter in parallel. In an experiment on studying the dependence of the current I flowing through a given resistor on the potential difference V applied across it, a student has to change the value of the current.
For doing this, he should change the a number of cells used b resistor itself c ammeter used in the circuit d Voltmeter used in the circuit.
Answer: a If we change the number of cells in electric circuit, the potential difference will change and as a result current flowing in the circuit changes. A milliammeter had Important Question Of Cbse 10th Class Science Full graduations marked 0, , , , and The space between 0 mark and mark is divided into 20 divisions.
If the pointer of the milliammeter is indicating the seventh graduation after mark, the current flowing in the circuit is a mA b mA c mA d mA. Answer: d If the circuit is closed for a long time, then current flows in it for a long time which results that the resistor is heated.
To determine the eguivalent resistance of two resistors connected in series, a student prepared two electric circuits, correct reading of ammeter in the circuits is [CCE ] a In circuit I, 1. Answer: b Equivalent resistance of two resistors 3. When parallel resistors are of three different values, the potential difference across its terminals is [CCE ] a greatest across smallest resistance b greatest across largest resistance c equal across each resistance d least across the smallest resistance.
Answer: c Potential difference across each resistor is same in parallel combination of resistors. A compass is to be placed near a bar magnet with unknown poles. Outside the magnetic field, the compass needle is pointing towards North as shown below:. Answer: c Magnetic field lines always point from North pole to South pole around the magnet.
Thus, compass needle follows the path difference of magnetic field lines. A bar magnet is broken into three parts X, Y and Z. Which diagram show the poles in X, Y and Z?
Answer: d When a magnet is broken into three parts X, Y and Z, each part is still a magnet and the strength of the magnetic force remains the same. An unmagnetised iron bar is placed near the end of a bar magnet. Which of the following diagram is correct?
Answer: b The end of the iron bar nearer to the South pole of the bar magnet becomes induced North pole while the other end is South pole. The diagram shows a current-carrying wire passing through the centre of a square cardboard. How do the strengths of the magnetic field at points X, Y and Z compare?
Answer: d The closer to the wire, the stronger is the magnetic field strength. Since, the magnetic field is circular. Y is the closest followed by X than Z. A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is on. The current as seen from points A and B in the plane of paper and on the axis of the coil is anti-clockwise and clockwise, respectively.
The magnetic field lines point from B to A. Answer: a The N-pole of the resultant magnet is on the face close to A because, the magnetic field lines enter in loop from B and come out from A. Also, as a matter of fact magnetic lines come out of the N-pole of magnet. Therefore, face close to A represents N-pole. The currents in A and B are same. A bar magnet is used to pick up an iron nail. At which parts X, Y and Z is the easiest for the magnet to pick up the iron nail?
Answer: c The region with the highest density of magnetic field lines has the greatest strength. If the key in the arrangement as shown below is taken out the circuit is made open and magnetic field lines are drawn over the horizontal plane ABCD, the lines are [NCERT Exemplar] a concentric circles b elliptical in shape c straight lines parallel to each other d concentric circles near the point O but of elliptical shapes as we go away from it.
Answer: c When the key is taken out the circuit is made open , no current flows through the wire, hence no magnetic field exists due to the conductor. Four metal rods are placed in turn inside the solenoid to attract paper clips. The table below gives the results of the experiment when current is switched on and off. Answer: c The core of the solenoid in a circuit breaker must be made of a soft type magnetic material which can be strongly magnetised but does not retain induced magnetism.
Permanent magnets can be made using hard magnetic materials. Which of the following is not the correct method to make permanent magnets? Answer: d The AC supply will mix up the direction of the magnetic domains. In fact, this is one of the methods to demagnetise magnets.
In the arrangement shown in figure, there are two coils wound on a non-conducting cylindrical rod. Initially, the key is not inserted. Then, the key is inserted and later removed. Then, a the deflection in the galvanometer remains zero throughout.
Thus, the galvanometer shows momentary deflections in opposite directions. Answer: d In the given arrangement, whenever an electric current through the first coil is changed, an emf is induced in the coil due to change in magnetic field lines which pass through the neighbouring second coil.
When key is inserted and removed, then the magnetic field lines passing through second coil increases and decreases in two cases respectively. Therefore, the direction of current in two cases is opposite. Which of the following is a non-renewable source of energy? Answer: c The fossil fuels are non-renewable sources of energy whereas wood, the Sun and wind are renewable sources of energy. Non-renewable sources of energy are those which are exhaustible and cannot be replaced, once they have been used.
They are also known as conventional sources of energy. Answer: d The thermal power plant generates electric power from heat produced by burning fossil fuel, i. Everyday we burn a large amount of fossil fuels to heat up water to produce steam. The steam so produced runs turbines to generate electricity. In a hydroelectric power plant more electrical power can be generated, if water falls from a greater height because [NCERT Exemplar] a its temperature increases b a large amount of potential energy is converted into kinetic energy c the electricity content of water increases with height d more water molecules dissociate into ions.
Answer: b In a hydroelectric power plant, more electrical power can be generated, if water falls from a greater height, because the rise in water level causes the increase in potential energy of water.
Thus, when it flows from higher position more amount of kinetic energy is formed by the conversion of higher potential energy and this kinetic energy in the form of moving water can produce more electrical power. The power generated in a windmill [NCERT Exemplar] a is more in rainy season, since damp air would mean more air mass hitting blades b depends on the height of the tower c depends on wind velocity d can be increased by planting tall trees close to the tower.
Thus, the power generated in a windmill depends on wind velocity. Choose the correct statement. Answer: a The Sun has been radiating an enormous amount of energy at the present rate for nearly 5 billion years and will continue radiating at that rate for about 5 billion years more, so the Sun can be taken as an inexhaustible source of energy. Which part of the solar cooker is responsible for greenhouse effect? Answer: c Glass sheet present in the solar cooker easily passes the radiation into the solar cooker and the radiation gets absorbed and that reflected back by the black coating is of longer wavelength and cannot pass back out through the glass.
Thus, glass sheet produces greenhouse effect in solar cooker. Ocean thermal energy is due to [NCERT Exemplar] a energy stored by waves in the ocean b temperature difference at different levels in the ocean c pressure difference at different levels in the ocean d tides arising out in the ocean.
Answer: b The water at the surface of the sea or ocean is heated by the Sun, while the water in deeper sections is relatively cold. Thus, ocean thermal energy is due to temperature difference at different levels in the ocean. The major problem in harnessing nuclear energy is how to [NCERT Exemplar] a split nuclei b sustain the reaction c dispose off spent fuel safely d convert nuclear energy into electrical energy.
Answer: c The major hazard of nuclear power generation is the storage and disposal of spent or used fuels. Improper nuclear waste storage and disposal result in environmental contamination as well as risk of accidental leakage of nuclear radiation. It happened in Chernobyl disaster , Fukushima Nuclear disaster caused great damage to the living beings and habitats.
Identify the original source of the energy which flows through a food chain? Answer: d All the living organisms get energy directly or indirectly from the sunlight reaching the surface of Earth. A teacher draws the pyramid of energy on board and writes A, B, C and D, in each trophic level as shown in the diagram given alongside. Which level represents the herbivores? Answer: c The trophic levels represent the transfer of food or energy through various steps or levels in the food chain. Producers harness the maximum energy followed by primary consumers, i.
Which of the following groups contains only biodegradable items? Answer: a , c and d substances that are broken down decomposed by the biological processes are said to be biodegradable e.
Which of the following constitutes a food-chain? Answer: b Each step of food chain form a trophic level. Producers grass forms the first trophic level, herbivore goat the second and carnivore human the third trophic level. Which of the following are environment- friendly practices?
Hence, all these practices are considered as environment friendly. Which of the following statements about food chain are correct? Answer: d A food chain is a series of organisms in an environment through which energy transfer occurs starting with a producer.
It proceeds in straight line. Food chain does not consist of branching lines. In class, the teacher explained the concept of food chain and energy flow. She made a diagram as given below and asked the students to identify the producer organism in the chain. Answer: b Cabbage is the producer component of this chain.
It produces food using sunlight and other components by photosynthesis process. Others are all consumers. An ecosystem includes a all living organisms b non-living objects , c both living organisms and non-living objects d sometimes living organisms and sometimes non-living objects.
Answer: c All the interacting organisms in an area taken together with the non-living constituents of the environment form Important Question Of Cbse 10th Class Science 2?? an ecosystem. Thus, an ecosystem consists of biotic components including all living organisms and abiotic components constituting physical factors like temperature, rainfall, wind, soil and minerals. In the following groups of materials, which group s contains only non-biodegradable items?
Answer: d Substances that cannot be broken down by biological processes in nature are non-biodegradable. On the other hand, substances that are broken down decomposed by biological processes are said to be biodegradable, e. Which of the following statement is incorrect? Answer: b Green plants prepare their food from inorganic compounds using radiant energy of the sun in the presence of chlorophyll. All green plants and blue-green algae are called producers as they can prepare food from inorganic substances by photosynthesis.
Producers capture the solar energy and convert it into chemical energy. What will happen if deer is missing in the food chain given below? Answer: d If deer is missing in the given food chain, there will not be sufficient food for the tigers. Some of the tigers will die because of starvation and hence, the population of tigers will decrease.
Since, grass is eaten by deers, the population of grass will also increase whefl deer is missing. In a class activity, two students were asked to collect different items from their fellow mates and classify them as biodegradable and non- biodegradable. All the items have been identified except three. Find out which one is non-biodegradable among these? Answer: d Both b and c , i. These products are made from plastic and hence are non-biodegradable. The diagram shows excretory losses from a rat to the environment.
Which of the following will not be returned to the ecosystem and recycled? Answer: b Heat energy cannot be recycled, it gets lost in the environment. The generated is returned through the carbon cycle. Salts are used by living organisms present in the ecosystem. Urea also returns to the nitrogen cycle. Which of the following limits the number of trophic levels in a food chain? Answer: a Decrease in energy at higher trophic levels limits the number of trophic levels in a food chain. At each trophic level, a large portion of energy is utilised for the maintenance of organisms that occur at that trophic level.
So, organisms at higher level gets less and less energy at successive levels. Some topics that the chapter cover are as follows:. Chemical Change - A chemical change is a type of change where one or more new substances are formed with different physical and chemical properties. Generally, this type of change is irreversible and permanent in nature.
For example, when iron reacts with copper sulphate solutions, ferrous sulphate and copper are obtained as the by-product of the reaction. Physical Change - Important Question Of Cbse 10th Class Science Studies A change where no new substance is formed. In this type of change, only the physical properties such as colour, shape or size are of the reactants change. These changes are reversible and temporary in nature. For example, boiling of water, where water changes into water vapour on boiling.
A chemical reaction is when one or more substances react and give rise to one or more substances as a product. The substances so formed can either be chemical elements or compounds. There are several factors that can help us determine a chemical reaction, and they are:. In a chemical reaction, there can be an evolution of gas. In a chemical reaction, there can be a significant change in temperature. A precipitate is formed in a chemical reaction.
Change in colour of the reactants. Change in the state of the reactants. There are various types of chemical reactions depending upon multiple factors. The chemical reactions are as follows:. Combination reaction. Decomposition reaction. Single Displacement reaction. Double Displacement reaction. Redox Reaction. Endothermic reaction. Exothermic reaction. Neutralisation reaction. Precipitation reaction. A Chemical equation is a symbolic representation of chemical reactions that involve chemical formulas and symbols.
It involves both the reactants and products. The reactants are written on the left side, while the products are written on the right side of the equation.
Chemical Symbol is a chemical representation given to an element. For example, The chemical symbol of Zinc is Zn. Valency refers to the combining capacity of an element. It can be defined as the number of electrons gained or lost by an atom while it undergoes a chemical reaction.
While writing a chemical reaction, we should keep some rules in mind, and those rules are as follows:. The reactants are written on the left side of the equation. The products are written on the right side of the equation. For solids, we write s. For liquids, we write l. For gas, we write g. For aqueous solution, we write aq.
A chemical equation is said to be balanced when the number of atoms of the elements on the reactant side is equal to the number of atoms of the elements on the product side. There are certain steps that you can follow to balance a chemical equation, and they are:.
Make a list of each element involved in the equation. Then identify the number of atoms present in each element on both reactant and product side. Multiply the number of atoms to make both reactants and product side equal.
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