Cbse class 10 science Term-2 notes

Carbon and its Compounds 

Chapter Wise

 Important Questions

 Class 10 Science

 

VERY SHORT ANSWER TYPE QUESTION [1 Mark] – Year 2007

Question.1 Give the names of the following functional groups:

(i) —OH (ii) —COOH

Ansswer. (i) Alcohol group (ii) Carboxylic acid group

 

VERY SHORT ANSWER TYPE QUESTION [1 Mark] – Year 2008

 

Question.2 What is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds?

Answer. —CH2— is the difference in the molecular formula of any two consecutive members of a homologous series of organic compounds.

SHORT ANSWER TYPE QUESTIONS[I] [2 Marks] – Year 2008

Question.3

(a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.

(b) (i) Name the products formed when ethanol burns in air. 

(ii) What two forms of energy are liberated on burning alcohol?

(c) Why is the reaction between methane and chlorine considered a substitution reaction?

Question.4

(a) Why are covalent compounds generally poor conductors of electricity?

(b) Name the following compound:

(c) Name the gas evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?

Question.5 

Name the carbon compound which on heating with excess of concentrated sulphuric acid at 443 K gives ethene.

Answer.

Question.6 What is meant by a sturated hydrocarbon?

Answer. Those hydrocarbons in w hich valency of carbon is satisfied by single bonds only are called sturated hydrocarbons.

Question.7 Name the compound formed when ethanol is warmed with ethanoic acid in the

presence of a few drops of cone.H2S04

Question.8 Draw the structure of CH3COOH molecule.

Question.9 Draw the structure of ethanol molecule.

Question.10 What happens when a small piece of sodium is dropped into ethanol? 

Answer. Hydrogen gas will be evolved.

SHORT ANSWER TYPE QUESTIONS[II] [3 Marks] – Year 2009

Question.11 What is meant by a functional group in an organic compound? Name the functional group present in

(i) CH3CH2OH

(ii) CH3COOH

(b) State one point of difference between soap and synthetic detergent.

Answer.

(a) Functional group is an atom or group of atoms or reactive part of compound, which determines chemical properties of compounds.

(i) —OH (Alcohol)

(ii) —COOH (Carboxylic acid)

(b) Soaps do not work well with hard water, detergents work well with hard water.

Question.12 Give reasons for the following observations:

(a) The element carbon forms a very large number of compounds.

(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.

(c) Use of synthetic detergents causes pollution of water.

Answer.

(a) Carbon forms large number of compounds since carbon is small in size and can form stable covalent bonds (catenation) and it shows tetravalency.

(b) Air holes of gas burner are made open (adjusted) so that air can pass through, which is needed for complete combustion, so that heated vessels do not get blackened.

(c) Some synthetic detergents are non-biodegradable, therefore, cause pollution of water.

Question.13 What is ethanoic acid? Write the formula of the functional group present in this acid.

What special name is given to its 5 – 8% solution in water? How does ethanoic acid react with sodium carbonate? Write a chemical equation of the reaction and common name of the salt produced.

Answer.

VERY SHORT ANSWER TYPE QUESTIONS[1 Mark] – Year 2010

Question.14 State two characteristic features of carbon which when put together give rise to large
number of carbon compounds.
Answer. (i) Catenation (ii) Tetravalency of carbon

Question.15 Write the structural formula of chloroethane.

Answer.

SHORT ANSWER TYPE QUESTIONS[I] [2 Marks] – Year 2010

Question.16 Write the name and molecular formula of an organic compound having its name suffixed with ‘-ol and having two carbon atoms in the molecule. With the help of a
balanced chemical equation indicate what happens when it is heated with excess of r cone.H2S04.
Answer.

Question.17 Write the names and molecular formula of two organic compounds having functional r group suffixed as ‘-oic acid’. With the help of a balanced chemical equation and explain what happens when any one of them reacts with sodium hydroxide.

Answer.

Heredity  and Evolution Chapter Wise Important Questions Class 10 Science

Text book solutions

Question 1.

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.

This suggests that the genetic make-up of the tall parent can be depicted as:

(a) TTWW

(b) TTww

(c) TtWW

(d) TtWw

Answer:

(c) TtWW

Question 2.

An example of homologous organs is :

(a) our arm and a dog’s fore-leg

(b) our teeth and an elephant’s tusks

(c) potato and runners of grass

(d) all of the above

Answer:

(d) All of the above

Question 3.

In evolutionary terms, we have more in common with :

(a) a Chinese school-boy

(b) a chimpanzee

(c) a spider

(d) a bacterium

Answer:

(a) A Chinese school-boy

Question 4.

A study found that children with light coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive ? Why or why not ?

Answer:

This information is not complete. On the basis of this, it cannot be decided light colour trait is dominant or recessive. So it cannot be said until one does not know the nature of this trait in the parents.

Question 5.

How are the areas of study-evolution and classification interlinked ?

OR

‘Two areas of study namely ‘evolution’ and ‘classification’ are interlinked”. Justify this statement. [AICBSE 2016]

Answer:

Classification of organisms is based on relative similarities and differences among organisms. Resemblances in organisms are because they have arisen from a common ancestor and differences in them are due to adaptations to different types of environment. Since the organisms can be graded in order of increasing complexity it indicates at the concept of evolution.

Question 6.

Explain the terms analogous and homologous organs with examples. [CBSE 2011,2013, 2014]

Answer:

Analogous organs : Those organs which have different basic structure (or different basic design) but have similar appearance and perform similar functions are called analogous organs.

For example, The wings of an insect and a bird are analogous organs.

Homologous organs : Those organs which have the same basic structure (or same basic design) but different functions are called homologous organs.

For example, The wing of a bat, flipper of a seal, front leg of a horse and arm of a man are homologous organs.

Question 7.

Outline a project which aims to find the dominant coat colour in dogs.

Answer:

Suppose a black homozygous male is mated with a white homozygous female. If the progeny has all black dogs then the dominant coat colour is black.

Question 8.

Explain the importance of fossils in deciding evolutionary relationships.

Answer:

Fossils play important role in providing evolutionary evidences because by knowning the age of fossils we can know about the evolution process of an organism.

For example, a fossil bird called archaeopteryx that looked like a bird had many other features of reptiles. It had feathered wings like those of birds, but teeth and tail like those of reptiles. Archaeopteryx is, therefore, a connecting link between the reptiles and birds, and hence suggests that the birds have evolved from the reptiles.

Question 9.

What evidence do we have for the origin of life from inanimate matter ? [CBSE 2011, 2014]

Answer:

A British scientist J.B.S. Haldane at first in 1929 suggested that life is originated from inanimate matter. According to him life must have developed from the simple inorganic molecules which were present at that time. Later, Miller and Urey in 1953 presented its evidences. They assembled an apparatus to create an early earth atmosphere which was supposed to consist of gases like methane, ammonia and hydrogen sulphide, etc. over water. This was maintained at a temperature just below 100°C and electric sparks were then passed through the mixture of gases to stimulate lightning for about one week. At the end of one week, it was found that about 15 per cent of carbon (from methane) had been converted into simple compounds and amino acids which make up protein molecules formed in living organisms. This experiment provides the evidence that the life originated from inanimate matter (or lifeless matter) like inorganic molecules.

VERY SHORT ANSWER TYPE QUESTION [1 Mark] -Year 2007

1. What is a gene? [Delhi]

Answer. Gene is the unit of inheritance. Gene is the part of a chromosome which controls the appearance of a set of hereditary characteristics.

SHORT ANSWER TYPE QUESTIONS [I] [2 Marks] -Year 2007

2. What is meant by analogous organs? Taking a suitable example, explain how they support the theory of Organic Evolution. [Delhi]

Answer. Analogous organs are those organs which I have different basic structural design and developmental origin but have similar appearance and perform similar functions.

Example: The wings of birds and bats look similar but have different design in their structure. They have a common function of flying but their origins are not common. So, birds and bats are not closely related.

3. What is a sex chromosome? [Foreign]

Answer. Sex chromosome is a chromosome that operates in the sex-determining mechanism of a species. Many animals have two different types of sex chromosomes. For example, in human there is a large X chromosome and a much smaller Y chromosome.

SHORT ANSWER TYPE QUESTIONS [II] [3 Marks] -Year 2007

4.Define ‘evolution’. Describe Darwin’s theory of evolution. [All India]

Answer. Evolution is the sequence of gradual changes which take place in the primitive organisms over millions of years and new species are produced. Since, the evolution is of the living organisms, so it is called ‘Organic Evolution’.

Darwin’s theory of Evolution: Charles Robert Darwin gave the theory of evolution in his famous book, ‘The Origin of Species’. The theory of evolution proposed by Darwin is known as ‘The Theory of Natural Selection’. It is also called ‘Darwinism’.

According to Darwin’s theory of evolution:

1-There is natural variation within any population and some individuals have more favourable variations than others.

2-Population remains fairly constant even though all species produce a large number of off springs.

3-This is due to ‘competition’ or struggle for existence between same and different species.

4-The struggle for survival within population eliminates the unfit individuals and those with ‘favourable variations’ survive and pass on these variations to their progeny to continue. This is called natural selection.

5-The favourable variations are accumulated over a long time period leading to the origin of a new species.

SHORT ANSWER TYPE QUESTIONS [I] [2 Marks] -Year 2008

5.”The sex of the children is determined by what they inherit from their father and not their mother.” Justify. [Delhi(C)]

Answer. It is because a child who inherits an X chromosome from her father will be a girl and one who inherits a Y chromosome from his father will be a boy. But all children inherit a X chromosome from their mother regardless of whether they are boys or girls.

6. Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]

Answer. Variation refers to the differences in the characters or traits among the individuals of a species.

Variations are beneficial to the species because:

1-They enable the organisms to adapt themselves in changing environment.

2-Variations form the basis of heredity.

3-They form the raw materials for evolution and development of new species.

7. Describe briefly four ways in which individuals with a particular trait may increase in a population. [Foreign]

Answer. The four ways in which individuals with a particular trait may increase in a population are as follows:

 Sexual reproduction results into variations.

The individuals with special traits survive the attack of their predators and multiply while the other will perish.

 Genetic drift provides diversity without any adaptation.

Variations in the species may lead to increased survival of the individuals.