Saturday, September 29, 2012

X CBSE | NCERT Solutions:Carbon and its compound Solved Important...

1.Q. Why carbon form covalent bond by sharing electron?

Ans: Carbon has four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration.  (i) it could gain four electrons forming C4-anion. But it would be difficult for the nucleus with six protons to hold on to ten electrons, that is, four extra electrons. (ii) It could lose four electrons forming C4+cation. But it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons.
Hence, it is difficult for the carbon to lose or gain four electrons therefore  carbon formcovalent bond by sharing electron

2.Q. Why do covalent compounds are in gaseous or liquid state at normal temperature and pressure.

Ans: due to Weak Vanderwaal’s forces present between the molecules of covalent compounds.  

3.Q. Why do covalent compounds have less melting and boiling points?

Ans: As energy required breaking the crystal is less due to the presence of weak Vanderwaal’s force.

4.Q. Why do covalent compounds are bad conductors of electricity?

Ans: Due to the absence of free electrons or free ions.

5.Q. Why graphite has high melting point?

Ans: Within each layer of graphite, every carbon atom is joined to three others by strong covalent bonds. This forms a pattern of interlocking hexagonal rings. The carbon atoms are difficult to separate from one another. So graphite also has high melting point.

6.Q.why is  diamond known as the hardest metal?

Ans: each carbon is  linked to four other carbon atoms forming regular and tetrahedral arrangement and this network of carbon atoms extends in three dimensions and is very rigid. This strong bonding is the cause of its hardness and its high density.

7.Q.Define term  allotropy?

Ans: Allotropy is the property by virtue of which an element exist in more than one form and each form has different physical properties but identical chemical properties. These different forms are called allotropes. The two common allotropic forms of carbon are diamond and graphite.

8.Q. Name the products formed when methane burns in :
(a) Sufficient supply of air. (b) Insufficient supply of air. 
Write the chemical equations for above reactions. 

Ans:When methane burns in a sufficient supply of air then Carbon dioxide and water vapours are formed.
CH4 + 2O2 -------burning---->   CO2 + 2H2O.
When methane burns in an insufficient supply of air then carbon monoxide and water vapours are formed.
2CH4 + 3O2 ---------->  2CO + 4H2O

Q. 9 Give any one test to distinguish between methane and ethene gases in the lab. Name the reaction by which ethene molecule can be converted into polythene.

Ans. Ethene gas decolourises the bromine water but methane being  a saturated hydrocarbon doesn't decolourise the bromine water.
CH2 = CH2 + Br2 (aq)  ------àCH2Br-CH2Br (1,2-dibromo ethane).
 Polymerisation is the reaction by which ethene molecule get converted into polythene.

10.Q. What is meant by homologous series? State any four characteristics.

Ans. The member of the same class of organic compounds such as alkanes when arranged in ascending order of their molecular mass differ from  each other by (-CH2) group are called homologous and series is known as homologous series.
The characteristics of homologous series are :
a. The members of a homologous series are represented by the same general formula.
b. The members of homologous series differ by (-CH2) group.
c. The members of same homologous series show similar chemical properties.
d. The members of same homologous series show different physical properties.

Links For   CBSE Class X Science Term-II
For Solved CBSE Exam questions Visit  Read more

Wednesday, September 26, 2012

8th science: Ch:Reaching the age of adolescence solved questions

CBSE Science  Chapter : Reaching the age of adolescence
Q1. What is adolescence?

Ans. It is the period of life when the body undergoes changes, leading to reproductive maturity.

Q2. Define puberty.

Ans. The stage when human body becomes sexually mature.

Q3.  What is adam’s apple?

Ans. The growing voice box in boys can be seen as a protruding part of the throat called adam’s apple.

Q4. What are secondary sexual characters?

Ans.These are the features that help to distinguish males from females.

Q5. Define the following terms. (a) Hormone (b) Endocrine glands

Ans. (a) Hormone- they are chemical messengers for various processes and activities in the body
        (b) Endocrine glands- the ductless glands which secrete hormones directly into blood.

Q6. Enlist the changes occurring in males and females during puberty.

Type of change
In girls
In boys
Increase in height
Sudden increase
Sudden in crease
Body shape
Waist widens
Shoulders broadens
Voice change
High pitched
Voice becomes deeper
Development of sex organs
Ovaries mature and releases eggs.
Testes matures and produces sperms

Q7. What is the role of hormones in initiating reproductive function?

Ans.1. Hormones from pituitary stimulate testes and ovaries to release testosterone and  estrogen  respectively.

3. These sex hormones reach to target sites via blood.

4. Then stimulate changes in the body at the onset of puberty.

Q8.  Discuss reproductive phase of life in women.

Ans. In females the reproductive phase of life begins at puberty and continues till they reach the age of 45-50 years. The egg begins to mature with the onset of puberty. One mature ovum is released by one of the  ovaries every month. The process is called ovulation. During this period, the walls of the uterus become thick  so as to receive fertilized egg.  Then this egg gets implanted in the uterus resulting in pregnancy.

Q9 Give reasons for the following :

a. Tadpoles growing in iodine deficient water have retarded growth.

Ans. The process of growth and development is regulated by thyroxine hormone which is produced by thyroid gland. Iodine is required for thyroxine production. That is why retarded growth is seen in tadpoles living in iodine deficient water.

b. Voice becomes hoarse in adolescent boys.

Ans. Sometimes the muscles of the growing voice box go out of control and the voice becomes hoarse.

c. Adolescents experience acne and pimples.

Ans. This is dues to increased activity of sebaceous (oil) glands in the skin.

d. Females have no role in determining gender of a child.

Ans. Y- chromosomes that leads to a boy offspring is contributed by male parent. That is thesperms are of two types, having either X or Y chromosome.

10. What are the causes of AIDS?

Ans. The causes of AIDS are:
1. Sharing needle of the syringe            
2. unprotected sex with infected person.        
3. blood transfusion from infected person to healthy one.
4. infected mother can pass HIV through milk to an infant.
8th Chapter: Reaching the Age of Adolescence
[Study Notes] by Educational service
CBSE Solved Questions Paper-1
CBSE Solved Questions Paper-2
CBSE Solved Questions Paper- 3
CBSE Solved Questions Paper- 4
VIII  Reproduction in Animals    
Reproduction in Animals  [E-NOTES]
CBSE Test Paper  [solved question]
CBSE Worksheet for practice
Reproduction & Endocrine [solved]

Saturday, September 22, 2012

CBSE Group Mathematical Olympiad, 2012 on 2 Dec 2012

CBSE Group Mathematical Olympiad, 2012

The Central Board of Secondary Education (CBSE) will conduct the 16th Group Mathematical Olympiad (GMO) on 2nd December 2012 for all its affiliated schools. The Group Mathematical Olympiads are conducted every year by the CBSE an aim to strengthen the knowledge of the students, enhance their innate problem solving skills and to identify talent at a young age.

This year the Group Mathematical Olympiad will be held on 2nd Dec 2012 at selected venues in different parts of the country leading to participation in the “International Mathematical Olympiad”.

In 1997, CBSE was granted the status of an independent group by the National Board of Higher Mathematics (NBHM) and since then CBSE has been conducting the Group Mathematical Olympiad (GMO) for students studying in its affiliated schools.

The top 30 students from the CBSE group will get to participate in the Indian National Mathematics Olympiad (INMO) conducted by the National Board of Higher Mathematics (NBHM). Selection at the national level would finally lead to participation at the International Mathematics Olympiad.

Who can participate in CBSE’s Group Mathematical Olympiad 2012
Any student studying in class XII, XI, X or IX can participate in the competition. However, there will be a common question paper for all participants.
Bright students from class VIII may also appear in RMO.
A school can sponsor up to five students for the competition.
The five students should be selected strictly on the basis of a screening test conducted by the school itself.

Fee to be paid for CBSE’s Group Mathematical Olympiad 2012

Every sponsored candidate shall remit a sum of Rs. 55/- as entry fee for the examination. The fee of the candidates should be forwarded by the principal of sponsoring school to the venue principal (centre) in the form of demand draft in favour of the principal of the venue school.

CBSE’s Group Mathematical Olympiad 2012 Exam Date

The 16th CBSE Group Mathematical Olympiad 2012 will be held on Sunday,2nd December, 2012. The duration of the examination will be 3 hours (1:00 pm to 4:00 pm)

Last date for Applying to CBSE’s Group Mathematical Olympiad 2012

The fee along with desired information about the sponsored students should reach the state coordinator by 10th October, 2012. In no case should the fee or documents be sent to the Board.

How to Apply for CBSE’s Group Mathematical Olympiad 2012?

The head of the participating schools will forward the names of sponsored students to the state coordinator nominated by the Board. The information about the sponsored candidates including name, father’s name, date of birth, school address, class, residential address, total marks obtained in the class one lower than in which he/she is studying, should be sent to the state coordinator along with the fee before the last date. The sponsored candidates should be bonafide students of the institution The admit card to be issued by the sponsored school should have complete information about the students. The admit card should also carry the signature of the student and his/her latest photograph duly attested by the principal.
Conduct of CBSE Group Mathematical Olympiad, 2012
| For the detailed information folder : Click Here
Mathematics TEST PAPER-01
Mathematics TEST PAPER-02
Mathematics TEST PAPER 03
Regional Mathematical Olympiad with solution -2011
(By pioneer mathematics) 

Maths Syllabus for 8th CBSE for SA-I & SA-II

Syllabus for 8th CBSE for SA-I & SA-II
Rational numbers
Linear equations in one variable
Understanding quadrilaterals
Practical geometry
Data handling
Square & square roots
Cube & cube roots
Comparing quantities
Algebraic expressions and identities
Visualizing solid figures
Exponents and powers
Direct & inverse proportions
Introduction to graphs
Playing with numbers
curriculum/Syllabus - Secondary School Examination

As per the KVS (HQ) Communication the following split up syllabus will continue for the year 2014-15.Hence no change in the split up syllabus  
Syllabus (C C E)CLASS VIII 2012-13

Class Wise Distribution of Syllabus
The page displays syllabus of all the classes of Government Schools of the DoE.  The syllabus has been divided according to the weeks and is available separately for each class from VI to XII.

This is a unique attempt to ensure the same level of teaching learning process throughout the department in all the schools irrespective of their location and the availability of staff.

It also helps in objective inspections on the basis of the syllabus covered in a particular class within a particular time frame.  This attempt also reduces the workload on the teachers while devising and forecasting their lesson plans for the forth coming week in advance as it is already available online.  It also ensures uniformity in teaching process at all places at all times.
Hindi Medium
English Medium
Urdu Medium

for Sample Paper Summative Assessment- II, March 2014 Class IX - X

Modified syllabus -2013 , Design of Assessment and sample questions including questions based on values in the subjects Hindi (Course A and B), English (Communicative), English(Language and Literature), Mathematics, Science, Social Sciences and Sanskrit to be used for Summative Assessment- II, March 2013 Class IX.
Hindi Course A    |    Hindi Course B    |    English (Communicative)    | English(Language and Literature)    |   Mathematics    |    Science    |    Social Sciences    |    Sanskrit
CBSE : Modified syllabus for Class X March 2014
Click here to download CBSE Circular
English (Communicative)
Hindi (Course B)
Social Sciences


Class X  Model   Answer  CBSE Exam.2013
Class X Model  Answer CBSE Exam.2012
Hindi Part: A