Q 1. The molecule of the alkene family is represented by the general formula CnH2n. Now answer the following questions:
(a) What do n and 2n signify?
(b) What is the IUPAC name of alkene when n = 4?
Ans.
Q 2. Insert gases are placed in a separate group in the modern periodic table :
(a) How many valence electrons do most of them have?
(b) Why are they unreactive?
Ans. (b) All elements of group 18 have completed their
octet so do not take or give electrons during
reaction, hence are unreactive.
Q 3. (a) Name an organism in which binary fission occurs in a definite orientation.
(b) Draw a neat diagram of a germinating seed and label on it the following :
Cotyledon, Plumule, Radicle.
Ans. (a) Leishmania
(b)
Q 4. Define the following processes of asexual reproduction.
(a) Spore formation
(b) Regeneration
(c) Multiple fission
Ans.
Ans. (a) Minute, Single-celled, thin, or thick-walled spores produced by sporangia develop into new life under suitable conditions.
(b) Organisms are cut into any number of pieces and each piece grows into a complete organism.
(c) Unicellular organisms divide into many daughter cells simultaneously.
Q 5. How does the process of budding differ from the process of spore formation?
or
What are sexually transmitted diseases? Name one STD which damages the immune system of
human body.
Ans.
Budding is the process of asexual reproduction where bud develops as an outgrowth of the body due to repeated cell division and grows into tiny individuals when matures which can later separate from the parent body e.g. hydra. Spore formation is the process of asexual reproduction in which tiny bulb-like structures called sporangia develop in organisms like Rhizopus. Sporangia contains minute, single-celled, and thin or thick-walled spores which grow into new organisms in suitable environment conditions.
or
Diseases that spread through the sexual contact, are called sexually transmitted diseases.
An STD which damages the immune system of human body is AIDS.
Q 6. Study the diagram given below and answer the questions that follow:
(a) Why do the iron filings arrange in such a pattern?
(b) What does this pattern demonstrate?
or
The diagram below shows a circuit containing a coil wound over a long and thin hollow cardboard tube. Copy the diagram.
(i) Show the polarity acquired by each face of the solenoid.
(ii) Draw the magnetic field lines of force inside the coil and also show their direction.‘
Ans.
(a) The iron filings arrange themselves in a pattern because they get attracted by the bar magnet. The pattern that they form can also be called the magnetic field lines of the bar magnet.
(b) The pattern is demonstrated that the magnetic field is the strong at poles of the magnet and the magnetic field becomes weaker if we goes far from the magnet. Magnetic filed lines emerge from the north pole of the magnet and ends at the south pole of the magnet.
or
(i) The polarity acquired by the two ends is as shown below. (A shows North and B showsSouth polarity).
(ii)
Q 7. Study the data of the following three categories A, B, and C.
(a) From the given three categories A, B, and C, pick the one which forms Dobereiner’s Triads.
(b) Why did Mendeleev place elements of Categories A, B, and C in three different groups?
(c) Is the Newland law of octaves applicable to all three categories? Give a reason to justify
your answer.
Ans.
Ans. (a) Category A forms Dobereiner’s triads.
(b) Mendeleev placed the elements of category A, B, and C in different groups because they all have different atomic masses.
(c) The law of octaves states that every eighth element has similar properties when the elements are arranged in the increasing order of their atomic masses. Therefore, it is applicable to all three ategories.
Q 8. Two elements X and Y have atomic numbers 12 and 16 respectively.
(a) To which period of the modern periodic table do these two elements belong?
(b) What type of bond will be formed between them and why?
(c) Give the chemical formula of the compound formed?
or
Account for the following :
(a) Noble gases are placed in a separate group.
(b) All the elements of the same group have similar chemical properties.
Ans.
| Element | Atomic number | Electronic configuration |
| X | 12 | 2, 8, 2 |
| Y | 16 | 2, 8, 6 |
(a) Both X and Y belong to the 3rd period because both have three shells.
(b) Ionic bond will be formed.
Reason: X is metal while Y is non-metal.
X has a tendency to lose 2 electrons while Y has a tendency to gain 2 electrons to attain the stable electronic configuration i.e., to complete the octet. Therefore, due to the transfer of electrons from the outermost shell, an ionic bond is formed between X and Y.
(c) Chemical formula: XY
or
(a) Noble gases like helium, neon and argon were discovered very late because they are very inert and present in extremely low concentrations in our atmosphere. Hence, they were placed in a new group without, disturbing the existing order.
(b) All the elements of a group have similar chemical properties because they have same number of valence electrons in their outermost shell.
Q 9. How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?
Ans. Yes; in Mendel’s experiment, when pure tall pea plants were crossed with pure dwarf pea plants, only tall pea plants were obtained in the F1 generation. On selling the pea plants of the F1 generation both tall and dwarf pea plants were obtained in the F2 generation. The reappearance of the dwarf pea plants in the F2 generation proves that the dwarf trait was inherited but not expressed in F1 generation. The recessive trait does not express itself in the presence of the dominant trait. So, it is possible that one trait may be inherited but may not be expressed in an organism.
Q 10. Calculate the total cost of running the following electrical devices in the month of September, if the rate of 1 unit of electricity is Rs. 6.00.
(i) Electric heater of 1000 W for 5 hours daily.
(ii) Electric refrigerator of 400 W for 10 hours daily.
Ans.
Q 11. Give two factors that could lead to the rise of new species.
Q 12. V –I graph for a conductor is as shown in the figure.
(i) What do you infer from this graph?
(ii) State the law expressed here
(iii) Name the physical quantity represented by the slope of this graph and its unit.
Or
The flow of current in a circular loop of wire creates a magnetic field at its center. How may the existence of this field be detected? State the rule which helps to predict the direction of this magnetic field.
Ans.
(i) Inference from graph V ∝ I
(ii) The law states the current passing through a conductor is directly proportional to the potential difference across the ends, provided
the physical conditions like temperature, density, etc., remain unchanges. This is ohm’s law.
(iii) The slope of the graph represents the resistance and the unit of resistance is ohm.
Or
The flow of current in a circular loop of wire creates a magnetic field at its center. How may existence of this field be detected ? State the rule which helps to predict the direction of this magnetic field.
Ans.
Take a cardboard sheet. Drill two fine holes P and Q on it along a straight line at a suitable distance.
Take an insulated copper wire loop and pass it through the holes so that the loop is in a vertical plane. Connect a 6-12 V battery B and a plug key K with the ends of the wire loop. Put a sensitive compass at the center point O of the cardboard. The compass rests in a north-south direction. Now put the plugin key K so that a current begins to flow in the loop as shown in Figure. We observe that the compass needle gets deflected. It shows that a magnetic field is set up at the center of the current-carrying circular loop.
The direction of the field is given by the right-hand rule.
Q 13. Find the current drawn from the baery by the network of four resistors as shown in the
figure.
Or
Study the following electric circuit and find the
(i) current flowing through the circuit and
(ii) the potential difference across 10 W resistor.
Q 14. Read the following case based passage and answer the questions given after passage. The rules for inheritance of such traits in human beings are related to the fact that both the father and the mother contribute practically equal amounts of genetic material to the child. This means that each trait can be influenced by both parental and maternal DNA.
(i) What is inheritance?
(ii) Who was the person who gave the three laws of inheritance?
(iii) What is the meaning of paternal and maternal DNA?
or
What is the phenotypic ratio of the dihybrid cross?
Ans.
(i) Traits of organisms can pass from the parents to their offspring and this mechanism is known as an inheritance.
(ii) Gregor Mendel was a monk and he discovered three laws that describe the inheritance of factors from parents to offspring.
(iii) The parental DNA is defined as the DNA that is received from the father while the DNA that is received by the mother is called the maternal DNA.
Or
Ans. Gregor Mendel discovered that the dihybrid cross yields a phenotypic ratio of 9 : 3 : 3 : 1.
Q 15. Read the following case-based passage and answer the questions given after the passage.
The mobile phone is an excellent communication device. Mobile phones use electromagnetic radiation in the microwave range. Part of the radio wave emitted by the mobile phone handset will be absorbed by the head.
The Head is in the ‘near field’ of radiation so most of the heating effect occurs in the head.
The temperature in the internal ear, brain increases by 1 degree or more. This adversely affects the
functioning of these organs since they have fluid-filled cavities. But a prolonged heating effect
can alter brain functions and hearing ability also. Other harmful effects such as Premature
Cataract, Confusion, and loss of memory may also be possible. The following figure shows how
mobile phone radiation penetrates the brain.
(i) Which radiations are used in mobile phones?
(ii) How does prolonged heating effect due to mobile radiations can effect adversely?
(iii) What precautions should be taken while using mobile phones?
or
In which part of our body, most of the heating effect occurs due to use of mobiles?
Ans.
(i) Electromagnetic radiations of microwave range are used in mobile phones.
(ii) Heating effect can alter brain functions and hearing ability also. Other harmful effects such as premature cataract, confusion and loss of memory may also be possible.
(iii) Try to consider mobile phone as a communication device and not an entertainment device. Even if you are not talking, the cell phone is emitting strong signals to keep a link with the base station.
Or
Head.