Q.1. Which gas is called dry ice ? Why ?
Ans: Solid C02 is called dry ice, because solid C02 gets converted directly into gaseous state without coming into liquid state when pressure is kept constant at one atmosphere.
Q.2. Elements with valency 1 are
(a) Always metals
(b) Always metalloids
(c) Either metals or non-metals
(d) Always non-metals
Ans: (c) Either metals or non-metals
Explanation: Metals and non-metals both can have valency 1.-Metals which have 1 valence electron and non-metals which have 7 valence electrons have valency 1. It is because metals lose their 1 electron and non-metals gain 1 electron to complete their octet.
Explanation: Given that number of protons in an atom = 3 and number of neutrons = 4 K, L Electronic configuration of 3L1 = 2, 1
As it has one valence electron/ therefore its valency is also 1.
Q.3. Two stones, one of mass 100 g and another of mass 2.0 kg are allowed to fall from the top of a high tower simultaneously. Then
(а) stone of mass 2.0 kg will reach the ground first.
(b) stone of mass 100 g will reach the ground first.
(c) both the stones will reach the ground simultaneously.
(d) nothing is certain.
Ans: (c) Both the stones will reach the ground simultaneously because both of them are freely falling under gravity.
Q.4. Question number 4 is based on the paragraph given below. Study this paragraph and answer the questions that follow.
The molecules of a gas are free to move about in any direction. Because of large intermolecular spaces, the gases are easily compressible. The kinetic energy of the molecules of gases is maximum and they move about randomly at a high speed. The randomly moving high speed molecules hit against the sides of containing vessel. The pressure exerted by any gas is due to the force exerted by its molecules on the sides of containing vessel.
We have observed that gases are highly compressible as compared to solids and liquids. The liquefied petroleum gas (LPG) cylinder that we get in our home for cooking or the oxygen supplied to hospitals in cylinders is compressed gas. Compressed natural gas (CNG) is used as fuel these days in vehicles. Due to its high compressibility, large volumes of a gas can be compressed into a small cylinder and transported easily.
(i). A gas fills all the space in a container in which it is kept because.
(a) the gases have large intermolecular spaces
(b) the molecules are not free to move
(c) the randomly moving molecules hit against the walls of container
(d) the molecules have large intermolecular forces of attraction.
(ii). When pressure is applied on a gas, it is converted to a liquid due to:
(a) increase in intermolecular forces of attraction between the particles
(b) increase in intermolecular distances between the particles
(c) decrease in intermolecular forces of attraction between the particles
(d) increase in kinetic energy of particles
(iii). The force per unit area exerted by the particles of the gas on the walls of container is called:
(a) atmospheric pressure
(b) pressure of the ga
(c) kinetic energy of the gas
(d) density of the gas
(iv). Which parameter of a gas is taken into account for filling it into the cylinders in the form of CNG and LPG:
(a) Low compressibility
(b) High kinetic energy
(c) High compressibility
(d) High density
Q.5. The gravitational force between two objects is F. If masses of both the objects are halved without changing the distance between them, then the gravitational force would become
An apple falls from a tree because of gravitational attraction between the earth and apple. If F1 is the magnitude of force exerted by the earth on the apple and F2 is the magnitude of foce exerted by apple on earth, then
(a) F1 is very much greater than F2
(b) F2 is very much greater than F1
(c) F1 is only a little greater than F2
(d) F1 and f2 are equal
Explanation: We know that according to the law of gravitation,
(G = Gravitational constant)
where, m1 and m2 are the masses of two objects respectively. And r is the distance between the two masses.
Now, according to the question, if masses of both objects are halved, i.e.,
So, new force,
(d) F1 and F2 are equal.
Explanation: According to Newton's universal law of gravitation, force exerted by one body to another body is equal in magnitude and opposite in direction.
Q.6. A solution contains 5 g of sodium chloride dissolved in 250 mb of water. The concentration of the solution in gram per 100 mL is
Ans: (b) 2.0
Q.7. An object is put one by one in three liquids having different densities. The object floats with and parts o f their volumes outside the liquid surface in liquids of densities d1 d2 and d3 respectively. Which o f the following statement is correct ?
(a) d1 > d2 > d3
(b) d1 > d2 < d3
(c) d1 < d2 > d3
(d) d2< d2 < d3
Q.8. Which one of the following disease is caused by protozoans?
Ans: (a) Malaria
Explanation: Malaria is caused by a protozoan Plasmodium. Influenza is caused by RNA virus, AIDS is caused by HIV and cholera is caused by bacterium Vibrio cholerae.
Q.9. Which of the following convention is not followed while writing scientific name ?
(a) The name of the genus begins with capital letter.
(b) The name of the species begins with small letter.
(c) When printed scientific name is given in italics.
(d) When written by hand the genus name and the species name should be underlined together.
Ans: (d) Both the names are underlined separately.
Q.10. Which of these options are not afunction of Ribosomes?
(i) It helps in manufacture of protein molecules
(ii) It helps in manufacture of enzymes
(iii) It helps in manufacture of hormones
(iv) It helps in manufacture of starch molecules
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (iv) and (i)
Q.11. List two human activities that would lead to air pollution.
Ans: (i) Increased use of vehicles run by burning fossil fuels.
(ii) Many industries release poisonous gases directly into the atmosphere causing air pollution.
Q.12. High blood pressure is a________disease while tuberculosis is an______diseases.
Ans: non-infectious, infectious.
Q.13. Assertion: The combustion of fossil fuels also increases the amount of suspended particles in air. These suspended particles could'be unbumt carbon particles or substances called hydrocarbons.
Reason: Presence of high levels of all these pollutants cause visibility to be lowered, especially in cold weather when water also condenses ou t of am This is known as smog and is a visible indication of air pollution.
Q.14. A ball is thrown vertically upwards. What is its momentum at the highest point ?
Ans: Zero as v = 0.
Q.15. Give reason for the following observations :
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.
Ans: (a) By absorbing heat energy from the surroundings, naphthalene balls slowly sublime, i,e., solid naphthalene balls directly get converted into vapours and disappear with time without leaving any solid.
(b) The molecules of perfume when enter in the air, diffuse in all directions as they are volatile and, therefore, we can smell the perfume sitting; several metres away.
Q.16. (i) What is one vibration in a second called as ?
(ii) A tuning fork produces 256 waves in four seconds. Calculate the frequency of the tuning fork.
Ans: (i) It is called hertz.
(ii) Frequency = Number of waves/Time
= 64 Hz.
Q.17. Distinguish between positive work and negative work. When you lift an object up, two forces act on it. Idendify these forces. Which one of the two does :
(a) Positive work
(b) Negative work ?
Justify your answer.
(a) State the law of conservation of energy.
(b) Give one example each of the following energy transformations :
(i) Heat energy into mechanical energy.
(ii) Mechanical energy into electrical energy.
Ans: Work done is said to be positive if the displacement of the object is along the direction of force applied. On the other hand, work is said to be negative if the displacement of the object is in a direction opposite to the direction of force applied. When a person lifts an object up, two forces are acting on the object.
These are :
(i) Force due to gravity F = mg, where m = mass of the object and g = acceleration due to gravity. The force acts in vertically downward direction.
(ii) A force F' applied by the person whose magnitude is equal to F but direction is opposite. Thus, F' = F = mg acts in vertically upward direction.
Out of these two forces (a) the force F' applied by the person does positive work because the displacement of object in upward direction is along the direction of force F. (b) The force of gravity F = mg does negative work because the force F = mg acts in vertically downward direction and displacement is upward.
(a) According to the law of conservation (transformation) of energy, we can neither create nor destroy energy. Energy may only be transforaied from one form to another such that total energy before and after the transformation remains exactly the same.
(b) (i) A heat engine transforms heat energy into mechanical energy.
(ii) An electric generator transforms mechanical energy into electrical energy.
Q.18. (a) How do substances like C02 and water move in and out of the cell ? Discuss.
(b) Why is the plasma membrane called a selectively permeable membrane ?
(i) Why is the cell called the structural and functional unit of life ?
(ii) Why is the plasma membrane called a selectively permeable membrane ?(iii) Name the factor which decides the movement of water across the plasma membrane.
Ans: (a) Substances like C02 (which is cellular waste and requires to be excreted out by the cell) accumulates in high concentrations inside the cell. In the cell's external environment, the concentration of C02 is low as compared to that inside the cell. As soon as there is a difference of concentration of C02 inside and outside a cell, C02 moves out of the cell, from a region of high concentration, to a region of low concentration outside the cell by the process of diffusion.
(b) The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. It also prevents movement of some other materials. The cell membrane, therefore, is called a selectively permeable membrane.
(i) Cells are the smallest unit which constitutes the body of all living organisms and perform certain basic functions that are essential for all living forms. Therefore, it is called the structural and functional unit of life.
(ii) Plasma membrane allows some substances to go in and out of the cell but does not allow some other substances to either enter or leave the cell. So, it is called a selectively permeable membrane.
(iii) Amount of substance (solute) dissolved in water.
Q.19. State the law of conservation of energy. With the help of an example explain the law of conservation of energy.
Ans: Law of conservation of energy states that "energy can neither be created nor destroyed but can be transformed from one form to another."
Explanation: Let us take the example of simple pendulum. We take a pendulum bob to one side and allow it to oscillate.
The pendulum bob has P. E. at the extreme positions A or B. It rises through a height h. Here/ the kinetic energy which is zero changes into potential energy. As it moves towards point O, its potential energy decreases progressively while the kinetic energy increases. As the bob reaches point O, the potential energy becomes zero while the bob possesses only kinetic energy.
It comes to rest due to air resistance and friction with the hook. Energy is lost in overcoming friction and air resistance is gained by surroundings but the total energy remains constant. Therefore, the total energy of pendulum and the surroundings remains conserved.
Q.20. State three prominent properties of metals which are generally not shown by non-metals.
Ans: (i) Metals have a bright metallic lustre (shine). Non-metals except iodine are not lustrous.
(ii) Metals are malleable (can be beaten into thin sheets) and ductile (can be drawn into wires). Non-metals are not malleable and ductile.
(iii) Metals are good conductors of heat and electricity. Non-metals are poor conductors of heat and electricity.
Q.21. How many times did you fall ill in the last one year ? What were the illnesses ?
(a) Think of one change you could'make in your habits in order to avoid any of / most of the above illnesses.
(b) Think of one change you would wish for in your surroundings in order to avoid any of/ most of the above illnesses.
Ans: I fell ill thrice in the last one year. At first time/I suffered from common cold, at second time, I suffered from influenza (eye-flu) and at third time, I suffered from diarrhoea.
(a) The change which I brought in my habits to avoid any of this type of illness in near future is:
(i) To remain away from people suffering from common cold or eye-flu.
(ii) To clean hands before meals and to take purified drinking water.
(b) Availability of purified drinking water all the time throughout the year.
Q.22. (i) Which of these is an acute ailment and why ?
Tuberculosis, Cancer, Diarrhoea, Elephantiasis.
(ii) State any two internal, non-infectious causes of a disease.
(iii) Name the organ that is targeted by the virus that causes jaundice.
Ans: (i) Diarrhoea, since it is a short term disease and does not: cause drastic long term effect on the person's general health.
(ii) Genetic abnormalities, excessive weight, lack of exercise
Q.23. What are maeronutrients ? From where do the plants get it ?
Ans: Nitrogen, phosphorus, potassium, calcium, magnesium and sulphur are macronutrients. These six nutrients are required by the plants for their growth in large quantities. Hence, these are called macro-nutrients.
Plants get these macronutrients from soil, in dissolved form, along with water. Nitrogen from atmosphere is fixed either by free-living or symbiotic microbes and made available for plants.
Q.24. In the folloiving example, try to identify the number of times the velocity of the hall changes: "A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards a player of his own team". Also, identify the agent supplying the force in each case.
Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s-1 and 1 m s-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 ms-1. Determine the velocity of the second object.
Ans: The velocity of the football changes four times:
First time, the velocity changes when the player applies force to kick the ball towards another player of his team.
Second time, the velocity changes when the other player kicks the ball towards the goal.
Third time, the velocity changes when the goalkeeper collects the ball by applying force in a direction opposite to the direction of the motion of the ball.
Fourth time, the velocity changes when the goalkeeper kicks the ball towards the player of his. Own team by applying force.
By law of conservation of linear momentum,
we have Momentum of the system before collision
= Momentum of the system after collision, hence
Q.25. You are provided with solution of substance 'X', How will you test whether it is saturated or unsaturated with respect to 'X' at a given temperature ? What happens when a hot saturated solution is allowed to cool ?
(a) 7 g of iron filings and 4 g of sulphur powder is treated with dilute sulphuric acid at room temperature. Name the gas produced,
(b) The same mixture is heated strongly, cooled and then treated with dilute sulphuric acid. Which gas would be produced ?
(c) What is the cause of this difference in results of chemical reaction in different conditions ?
Ans: When no more quantity of 'X substance can be dissolved in a solution at a given temperature,
then the solution is saturated with respect to "X: When a hot saturated solution is allowed to cool, crystals of substance separate out from the solution.
(a) The mixture of iron filings and sulphur reacts with dilute sulphuric acid to produce hydrogen gas at room temperature.
(b) When the mixture is strongly heated in a fixed ratio 7; 4 to form compound namely iron sulphide, when cooled and treated with dil. sulphuric acid gives rotten egg smelling. Hydrogen sulphide gas is evolved.
(c) The difference in behaviour is due to properties of compound which are different from those of its constituents, while properties of mixture are the same as the properties of the constituents.
Q.26. (a) Write the chemical formulae of:
(i) Silver nitrate
(ii) Magnesium sulphate
(iii) Potassium carbonate
(iv) Barium chloride
(v) Sodium phosphate
(vi) Sulphur dioxide
(b) Define Avogadro Number. Convert 2 moles of Magnesium sulphate sample into number of molecules present in the sample.
(a) Write the formula of the compounds formed by the following ions:
(i) Cr3+ and SO42-
(ii) Pb2+ and NO31-
(b) State the significance of one mole.
(c) Which has more number of atoms: 100 g of sodium or 100 g of iron.
(At. mass : Na = 23 u, Fe = 56 u)
Ans: (a) (i) AgNO3
(b) The number of particles (atoms, molecules or ions) present in 1 mole of any substance is fixed, with a value of 6.022 x 1023 This is an experimentally obtained value. This number is called the Avogadro Constant or Avogadro Number (represented by N0).
No. of molecules in 2 moles of MgS04 = 2 x 6.022 x 1023 = 12.044 x 1023
(b) One mole means 6.022 x 1023 particles of a substance.
One mole of an element contains 6.022X1023 atoms of an element.
One mole represents one gm formula mass of a substance.
Q.27. Define the following :
Atomic number, mass number, isotopes, isobars and valency.
Ans: Atomic number : The number of protons or electrons present in an atom of an element is called atomic number. For example, atomic number of oxygen is 8.
Mass number: Sum of the number of protons and neutrons present in an atom of an element is called mass number. For example, the mass number of oxygen is 16.
Isotopes: Atoms of the same element having the same atomic number but different mass number are called isotopes. For example,and are isotopes of carbon.
Isobars: Atoms of different elements having different atomic numbers but same mass number are called isobars. For example and Ca are isobars.
Valency: The number of electrons which it gains, shares or donates to the other atoms to form a compound is called valency. It is also called the combining capacity cf an element. For example, sodium has a valency of one.
Q.28. Carry out ike following osmosis experiment:
Take four peeled potato halves and scoop each one out to make potato cups. One of these potato cupt should he made from a boiled potato. Put each potato cup in a trough containing water. Now,
(a) Keep cup A empty.
(b) Put one teaspoon sugar in cup B.
(c) Put one teaspoon salt in cup C.
(d) Put one teaspoon sugar in the boiled potato cup D.
Keep these far two hours. Then observe the four potato cut and answer the following:
(i) Explain why water gathers in the hollowed portion of B and C.
(ii) Why is potato A necessary far this experiment ?
(iii) Explain why water does not gather in the hollowed o portions of A and D.
(a) What are the consequences of the fallowing conditions
(i) A cell having higher water concentration than the surrounding medium.
(ii) A cell having lower water concentration than the surrounding medium.
(iii) A cell having equal water concentration to its surrounding medium.
(b) Name the materials of, which the cell membrane and cell wall are composed of.
Ans: (i) The water gathers in the hollowed portion of B and C due to the process of osmosis. Since the concentration of solute (sugar in cup B and salt in cup C) is higher inside the cup as compared to the water which is outside the cup. Therefore, water (solvent) from its higher concentration (outside the cup) will move towards the lower concentration (inside the cup). This process of osmosis (moving in of solvent) is known as endosmosis.
(ii) Potato A acts as a control for the experiment. This is very necessary for comparing the results of the experiment.
(iii) Water does not gather in the hollowed out portions of A and D because of the following reasons:
(a) The hollowed portion of potato A is empty. Thus, there is no concentration difference and, therefore, no osmosis takes place.
(b) The hollowed portion of potato D contains sugar inside it but this potato is boiled one. Therefore, osmosis will not take place as its semipermeable membrane is destroyed by boiling.
(a) (i) The cell will loose water by osmosis, therefore, the cell will shrink. (Hypertonic solution)
(ii) The cell will gain water by osmosis therefore, the cell will swell up. (Hypotonic solution)
(iii) In case of equal concentration there will, be net movement of water, therefore, the cell will stay at same size. (Isotonic solution)
(b) • Cell membrane is composed of lipids and proteins.
• Cell wall is composed of cellulose.
Q.29. (i) To which division of plantae do algae belong? Write one characteristic of the division. Give two examples.
(ii) Name the group:
(a) which includes unicellular eukaryotic organisms.
(b) in which mode of nutrition is saprophytic.
(c) in which seeds are not closed in fruit.
(iii) Classify flowering plants on the basis of the number of cotyledons present in the seed ?
(a) State two characteristic features of group Mollusca.
(b) Identify the organisms on the basis of the following features:
(i) A Reptile with four chambered heart
(ii) An Egg laying mammal
(iii) An Autotrophic Moneran
Ans: (i) Algae belongs to Thallophyta
Thallophytes : Body is not differentiated, predominantly aquatic. Examples : Cladophora, Spirogyra, Celothrise, Chara
(ii) (a) Protista
(iii) On the basis of the number of cotyledons present in the seed, flowering plants/ angiosperms are classified as Monocots (1 cotyledon in seed) and Dicots (2 cotyledons in seed)
(a) Features of group Mollusca :
(i) Bilateral symmetry and the coelom ic cavity is reduced.
(ii) There is little segmentation. They have an open circulatory system and kidney-like organs for excretion.
(b) (i) Crocodile
(iii) Blue-green algae,/Cyanobacteria
Q.30. (a) List three characteristic features of kingdom Monera.
(b) Write two examples each :
(i) Egg laying mammals
(ii) Organisms with open circulatory system
Ans: (a) The identifying features of kingdom Monera are as follows:
(i) They are prokaryotes. Membrane bound cell organelles are absent. They have naked genetic material called nucleoid.
(ii) Monerans are basically unicellular. In filaments and colonies the cells are similar and independent.
(iii) Both autotrophic and heteratrophic mode of nutrition are found.
(iv) This kingdom includes bacteria, blue green algae or cyanobacteria and mycoplasma.
(v) Some representatives of this kingdom have a cell wall and some do not have it.
(b) (i) Egg laying mammals - Echidna, Duck billed platypus
(ii) Organisms with open circulatory system - Phylum Arthropoda and Mollusca.