Ques 1: Evaporation causes cooling. Give reason.
Ans: During evaporation, heat is absorbed from the nearest surrounding particles. So, their kinetic energy decreases as a result, cooling occurs.
Ques 2: A student mixed starch with water. Then after boiling it with continuous stirring, what did he observe?
Ans: He observed that starch formed a translucent mixture.
Ques 3: What is the boiling point of water in °C and in Kelvin?
Ans: The boiling point of water is 100°C or 373K.
Ques 4: To determine the melting point of ice, where should a thermometer be kept?
Ans: The thermometer should be kept with its bulb in the ice cubes.
Ques 5: Name the first step of separation from a mixture of common salt, sand and ammonium chloride.
Answer: The first step is sublimation. (Sublimation will remove ammonium chloride. Sand will be removed by filtration. Evaporation will give the common salt.)
Ques 6: What will happen when a suspension of chalk and water is subjected to filtration?
Ans: The chalk particles will be left on the filter paper.
Ques 7: Among true solution, colloidal solution and suspension, which cannot pass through the filter paper?
Ques 8: When you kick a stone, you get hurt. Why?
Ans: It is due to the Newton's third law of motion as kick is the action and hurting the foot is reaction.
Ques 9: What is the least count of a thermometer which has 19 graduations between 10° C and 20° C?
Ans: 0.5°C is the least count.
Ques 10: Name the process by which mixture of common salt and water can be separated completely.
Ques 11: Define ATP.
Ans: ATP Adenosine Triphosphate is energy unit formed inside mitochondria.
Ques 12: Which chemical is used to test the presence of metanil yellow colour of dal
Ans: HCl is used to test the presence of metanil yellow colour in dial. It gives pink colour.
Ques 13: Define pure substance. Write its two characteristics.
Ans: A homogeneous material containing particles of only one kind and has definite properties throughout is called a pure substance.
(i) A pure substance is always homogeneous in nature.
(ii) It has a definite set of properties.
Ques 14: When dropped from the same height a body reaches the ground quicker at poles than at the equator. Give reason.
Ans: When the initial velocities and the distance travelled are the same, time taken for a body will be smaller if the acceleration due to gravity is more. As we know, acceleration due to gravity is more at the poles than at the equator. So, when dropped from the same height a body reaches the ground quicker at poles than at the equator.
Ques 15: (i) What happens to the temperature of water, when it boils?
(ii) At 0°C or 273 K, what is the physical state of water?
Ans: (i) The temperature of water remains the same, because it remains constant at boiling point.
(ii) Both solid and liquid, because both solid and liquid coexist at melting point.
Ques 16: (i) In the experiment to find the relationship between weight of the rectangular block lying on a horizontal table and the applied force, a boy observes that the block begins to slide over the table when the spring balance reading is 10 N. If the reading of the spring balance is 5 N, then what will be the force of friction that will come into play?
(ii) When a body actually begins to move over the surface of another, name the frictional force which will come into play?
(i) 5 N. Because before the applied maximum force to just move the block, the applied force has been exactly balanced by the force of friction which is acting at the interface of the block and the horizontal surface of the table. The block remains at rest.
(ii) Kinetic friction comes In to play. It is because when the limiting friction is overcome by the applied force, the body begins to move and the limiting friction is converted into kinetic friction.
Ques 17: State the role of epidermis in plants.
Ans: Role of epidermis in plants
(i) It acts as protective tissue or covering tissue of plant body.
(ii) It protects plant from excessive heat or cold and from the attack of fungi and bacteria.
(iii) It allows exchange of gases and transpiration through stomata.
Ques 18: (i) Who coined the term cell?
(ii) Two cell organelle which have their own genetic material.
Ans: (i) Robert Hooke coined the term cell.
(ii) The two cell organelles, which contain their own genetic material are lissome and mitochondria.
Ques 19: (i) A spoonful of salt is added to a beaker containing 250 mL of water with continuous stirring. State two observations that you will make.
(ii) Account for your observations.
Ans: (i) (a) Salt completely disappears in water.
(b) Volume of water does not increase.
(ii) Since, there is a lot of space between water molecules, the salt molecules disappear into these spaces.
Ques 20: What is meant by solubility? How is it expressed what are the factors on which solubility depend?
Ans: The amount of solute that will dissolve in a given amount of solvent at a particular temperature is called solubility. Solubility is expressed as grams of solute per 100 of solvent and for gases in parts per million of solvent.
Solubility depends upon (i) Nature of solute (ii) Nature of solvent and (iii) Temperature.
Ques 21: Draw velocity-time graphs for the following situations.
(i) When the body is moving with uniform velocity.
(ii) When body is moving with variable velocity but uniform retardation.
(iii) When body is moving with variable velocity and variable acceleration.
Ques 22: Which of the following has more inertia?
(i) A rubber ball and a stone of same size.
(ii) A bicycle and a train.
(iii) A five rupees coin and a one rupee coin.
Ans: Mass of a body is the measure of inertia, i.e., a body with more mass has more inertia. So,
(i) Stone has more inertia.
(ii) Train has more inertia.
(iii) Five rupees coin has more inertia.
Ques 23: State the action and reaction in the following cases,
(i) A book lying on a table.
(ii) Moving rocket
(iii) A moving train colliding with a stationary train.
(iv)Hammering a nail
(v)Kicking a stone
(vi) A person moving on the floor.
Ans: (i) Action Book exerts a force downwards equal to its weight. Reaction Table balances it by equal reaction in upward direction on the book.
(ii) Action Rocket exerts force on the gases to expel them backwards. Reaction The gases exert equal and opposite force on the rocket.
(iii) Action Force exerted on the stationary train. Reaction Moving train experience equal and opposite force.
(iv) Action Force exerted on the nail. Reaction Hammer experiences an equal and opposite reaction.
(v) Action Force exerted at the stone by foot. Reaction Stone exerts an equal reaction on foot by hurting it.
(vi) Action Person pushes his foot against the ground backwards. Reaction Ground exerts an equal and opposite force on his feet.
Ques 24: Give three examples to illustrate the importance of universal law of gravitation.
Ans: (i) It is the gravitational pull of earth, which keeps us and other bodies firmly on the ground.
(ii) The motion of the moon around the earth and the motion of planets around the sun is due to gravitational force between them.
(iii) The tides formed in sea arc due to the gravitational pull evened by the sun and the moon on the surface of water.
Ques 25: What do you mean by
(i) squalors epithelium and columnar epithelium?
(ii) voluntary muscles and involuntary muscles?
Ans: (i) Squalors epithelium: It is a type of epithelial tissue, which consist of extremely thin flat cells forming delicate lining e.g., esophagus and lining of mouth.
Columnar epithelium: It is also a type of epithelial tissue, which consists of tall cells which are pillar-like having elongated nuclei e. g., inner lining of intestine.
(ii) Voluntary muscles: They are attached to bones and help in body movements and so called skeletal muscles. These muscles helps in all voluntary movement of body. These found in body wall, face, neck etc.
Involuntary muscles: These muscles do not work according to our will and occur as bundles or sheets. These are found in iris of eye, in uterus etc.
Ques 26: Which tissue smoothens the bone surface at joints. State its structure and function with the help of diagram.
Ans: Cartilage smoothens bone at joints surfaces. It is a specialised connective tissue, which is compact and less vascular having an extensive matrix of delicate network of collagen fibres. It provide flexibility and support to body parts and smoothens bone surfaces at joints. It is present in nose, ear, trachea, larynx etc.
Ques 27: (i) What is the organic farming?
(ii) List any three methods for insect pest control.
Ans: (i) Organic farming: It is a farming system with minimal or no use of chemical, as fertilizers, herbicides, pesticides etc., and with maximum input of organic manures, recycled farm-wastes, use of bio-agents such as culture of blue-green algae in preparation of bio fertilizers.
(ii) Methods of insects pest control are:
(a) By spraying contact insecticides e.g., ablation, linden.
(b) By mixing insecticides in soil, e.g., chloropyriphos.
(c) By spraying systematic insecticides e.g., dimethoate.
Ques 28: State some factors responsible for losses of grains during storage. Give one preventive measure to control such storage.
Ans: Factors responsible for losses of grains during storage are:
(i) Biotic factors These are insects, birds, rodents, mites and bacteria.
(ii) Biotic factors These are moisture, humidity and temperature. Preventive and control measures are used before the grain are stored for future used.
They include – Strict cleaning of produce before storage. – Proper drying of produce first in sunlight and then in shade. – Fumigation by using chemicals that can kill pests.
Ques 29: Give reason for the following observations.
(i) Water at room temperature is a liquid.
(ii) Naphthalene balls disappear after sometime without leaving any solid.
(iii) Sponge through compressible is a solid.
(iv) We can get smell of agarbatti sitting several metres away.
(v) Rate of evaporation of an aqueous solution decreases with increase in humidity.
Distinguish between solids, liquids and gases in a tabular form under the following characteristics.
(ii) Force of attraction
(iv) Intermolecular spaces
(v) Kinetic energy of particles
Ans: (i) Water is liquid at room temperature because:
(a)Intermolecular spaces are very large.
(b)Intermolecular forces of attraction between its molecules are less and kinetic energy is more. Hence, water molecules can interchange their spaces easily. So, it is liquid.
(ii) Naphthalene balls absorb heat energy from the surroundings and slowly sublime i.e., directly get converted into vapors from solid phase and disappear with time, without leaving any solid.
(iii) Sponge has minute holer in which air is trapped. On pressing it, the air is expelled out and we are able to compress it.
(iv) In air the molecules of agarbatti diffuse in all directions therefore, we can smell it from a large distance apart.
(v) Air around us cannot hold more than a definite amount of water vapour at a given temperature. So, with increased humidity air is already rich in water vapours, it cannot take up more water hence, rate of evaporation of water will decrease.
Difference between solids, liquids and gases
|Rigidity||These are rigid and maintain their hardness and shape.||These are fluids and flow easily.||These are also fluid and capable of infinite of infinite expansion.|
Force of attraction
|Strongest. Which keep the particles together.|
Comparatively weaker but keep the particles within the bulk of liquid
Extremely weak. Here particles are free to move in all direction.
|Compressibility||Almost incompressible||Relatively incompressible.||Highly compressible|
|Intermolecular spaces||Approximately negligible.|
Lntermediate between solid and gas.
|Kinetic energy of particles||Very low||Low||High|
Ques 30: How can you separate a mixture of two miscible liquids? Take one example. Or Distinguish among true solution, suspension and colloid in a tabular form under the following characteristics.
(i) Type of mixture
(iv) Size of solute
(v) Visibility of particles
Ans: Example To separate acetone and water from their mixture.
Procedure (i) Take the mixture in a distillation flask. Fit it with a thermometer.
(ii) Set the apparatus as shown in the figure given below.
(iii) Heat the mixture slowly and note the reading of thermometer.
(iv) The acetone vaporizes condenser in condenser an can be collected in the beaker.
(v) Water is left behind in the distillation flask.
Difference between true solutions, suspension and colloid
|Type of mixture|
Heterogeneous but appears to be homogeneous.
Stable, particles do not settle down on keeping.
|Not stable, particulars settle down filter paper.|
Stable, particles do not settle down on keeping.
Passes through filter paper.
Do not pass through filter paper.
Passes through filter paper.
Size of solute
Very small i.e., less than 10-3 cm in diameter.
|Quite large i.e., large than 10-5 cm in diameter||Between 10-7 cm and 10-5 cm in diameter|
|Visibility of particles||Not visible even with a powerful microscope.||Visible even with naked eyes.||Visible with the help of a microscope|
Ques 31: (i) What is pasturage? How it is related to honey production?
(ii) Name two local varieties of bees used for honey production.
(i) Name two indigenous breeds of cow.
(ii) What is hybridization?
(iii) Differentiate between macronutrients and micronutrients.
Ans: (i) Pasturage: It is availability of flowers to the bees for nectar and pollen collection. The value and taste of honey depends upon pasturage, the kind of flower available will determine the taste of honey.
(ii) Apis cerana and Apis dorsata.
(iii) Some advantages of bee-keeping are:
(a) It needs low investments, so farmers use it as additional income generating activity.
(b) It also helps in cross-pollination of crops because honey bees transfer pollen grains from one flower to another, while collecting nectar.
(c) Bee-wax propolis bee venom and royal jelly are other products obtain from bee-keeping.
(i) Red Sindhi and Sabinal.
(ii) Hybridization It is process of interbreeding between individuals of different species.
It is of two types
(a) Interspecific hybridization
(b) Intraspecific hybridization
|These are essential elements utillised by the plant in large quantities.||These are essential elements utilized by the plant in small quantities.|
|The six essential nutrients from macronutrients are nitrogen. Phosphorus. Potassium, calcium, magnesium and suplhur.||The seven essential nutrients from the micronutrients are iron. Boron, manganese, zinc, copper, molybdenum and chlorine.|
Ques 32: Given below is a diagrammatic sketch of certain generalized cell.
(i) Name the part numbered as 1 to 8.
(ii) It is plant cell or an animal cell. Give two reasons to support your answers.
(iii) Give one functions of parts marked as 1, 6 and 8.
(i) The Part Numbered
7. Cell membrane
8. Cell wall
(ii) It is plant cell because
(a) it has definite shape with cell wall.
(b) chloroplast are present.
(a) Chloroplast They synthesize food by trapping solar energy so they are called kitchen of the cell.
(b) Nucleus It control all the activities of the cell.
(c) Cell wall It protect the plasma membrane and internal structures of the cell and helps in transporting various substances in and out of the cell.