CBSE Class 10 Science Control And Coordination Worksheet Set F

Question: Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms, e.g. hydrogen. After the formation of four bonds, carbon attains the electronic configuration of
(a) Helium
(b) Neon
(c) Argon
(d) Krypton
Answer: b

Question: A molecule of ammonia (NH₃) has
(a) only single bonds
(b) only double bonds
(c) only triple bonds
(d) two double bonds and one single bond
Answer: a

Assertion-Reason Type Questions 

For question numbers 1 and 2 two statements are given-one labeled as Assertion (A) and the other labeled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both ‘A’ and ‘R’ are true and ‘R’ is correct explanation of the assertion.
(b) Both ‘A’ and ‘R’ are true but ‘R’ is not correct explanation of the assertion.
(c) ‘A’ is true but ‘R’ is false.
(d) ‘A’ is false but ‘R’ is true.

Question: Assertion: Carbon forms covalent compound with chlorine of formula CCl₄.
Reason: Carbon has 4 valence electrons, valency 4, chlorine has 7 valence electrons, valency 1.
Answer: a

Question: Assertion: Carbon forms very large number of compounds.
Reason: It is due to property of catenation and tetravalency
Answer: a

Very Short Answer Type Questions

Question: How is spinal cord protected?
Answer: Vertebral column made by vertebrae protects the spinal cord.

Question: Define ‘reflex action’.
Answer: Reflex action is a sudden, involuntary, spontaneous response to the stimulus that is usually helpful to protect ourselves from any kind of harm.

Question: How is nerve impulses get transmitted across the synapse?
Answer: Neuron ending transmit the nerve impulse to dendrite of next neuron through the chemical (neurotransmitter).

Question: What are hormones?
Answer: Hormones are the chemical substances secreted in trace amounts by specialised tissue called endocrine glands.

Question: Name two tissues that provide control and coordination in multicellular animals.
Answer: (i) Nervous tissue (ii) Endocrine tissue.

Question: What is synapse?
Answer: Synapse is the functional junction between two neurons. It is a gap junction point between nerve endings of one neuron and dendrites of another neuron.

Question: Which mechanism control timing and amount of hormone released?
Answer: Feedback mechanism.

Question: Give one example of chemotropism.
Answer: The growth of pollen tube towards ovule.

Question: At the time of puberty, both boys and girls show lots of changes in appearance. Name the hormones responsible for these changes.
Answer:  Testosterone in male and oestrogen in females.

Question: Define catenation. 
Answer. The property of self-linking of atoms of an element through covalent bonds in order to form straight chain, branched chains or cyclic chains of different sizes is called catenation.

Question: Name the plant hormone responsible for the promotion of cell division.
Answer: Cytokinin.

Question: Define‘Chemotropism’.
Answer: Chemotropism is a nastic response towards the chemicals like the germination of pollen tube when pollen grain lands on stigma.

Question: What will happen to a plant shoot if sunlight falls on it from one direction only? What do you call this movement?
Answer: Shoot will bend towards light. Phototropism.

Question: Name the sensory receptors found in the nose and on the tongue.
Answer: Olfactory receptors, gustatory receptors.

Question: How are covalent bonds formed? 
Answer. Covalent bonds are formed by equal sharing of electrons.

Question: Why covalent compounds are poor conductors of electricity? 
Answer. It is because covalent compounds do not form ions.

 Question:Covalent compounds have low melting and boiling point. Why? 
Answer. It is because they have weak van der Waal’s forces of attraction between molecules therefore have low melting and boiling points.

Question: 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: Why are most carbon compounds poor conductors of electricity? 
Answer. Carbon compounds form covalent bonds/do not dissociate into ions/do not have charged particles (ions).

Question: Which element exhibits the property of catenation to maximum extent and why? 
Answer. Carbon since it forms strong covalent bond, due to smaller atomic size.

Question: Explain why carbon generally forms compounds by covalent bonds or do not form ionic compounds.
Or
Give reason why carbon neither forms C⁴⁺ cations nor C^4– anions but form covalent compounds which are bad conductors of electricity and have low melting and boiling points.
Or
Carbon has four electrons in its valence shell. How does carbon attain stable configuration?
Answer. Carbon as 4 valence electrons. It cannot lose 4 electrons because very high amount of energy is needed. It also cannot gain four electrons because 6 protons cannot hold 10 electrons.
It can share four electrons to form four covalent bonds. Covalent compounds do not conduct electricity because they do not form ions. They have low melting and boiling points due to weak forces of attraction between molecules.

Question: Carbon has four electrons in its valence shell. How does carbon attain stable electronic configuration.
Answers. By sharing four electrons with other atoms.

Question: 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.

Question: What is meant by a saturated hydrocarbon?
Answer. Those hydrocarbons in which valency of carbon is satisfied by single bonds only are called saturated hydrocarbons.

Question: How many covalent bonds are there in a molecule of ethane (C₂H₆)?
Answer. There are 7 covalent bonds in a molecule of ethane.

Question: Give the names of the following functional groups:
(i) —OH (ii) —COOH
Answer. (i) Alcohol group (ii) Carboxylic acid group

Question: 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

Short Answer Type Questions

Question: Classify the following carbon compounds into two homologous series and name them.
C₃H₄, C₃H₆, C₄H₆, C₄H₈, C₅H₈, C₅H₁₀
Answer : 
The series of organic compounds having same functional group and similar chemical properties is called homologous series.
Alkene: C₃H₆, C₄H₈, C₅H₁₀
Alkyne: C₃H₄, C₄H₆, C₅H₃

Question: What is meant by hydrotropism? Give an example.
Answer: The response of a plant towards water is called hydrotropism. The roots of plants show positive hydrotropism.

Question: Tendrils encircle or coil around the object in contact with it. Elaborate.
Answer: Tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus, cling to it.

Question: C₃H₆, C₄H₈ and C₅H₁₀ belong to same 1 homologous series.
a. Define homologous series.
b. Why the melting and boiling point of C₅H₁₀ is higher than C₄H₃?
c. Arrange these hydrocarbons in order of increasing boiling points.
Answer : 
a. The series of organic compounds having same functional group and similar chemical properties is called homologous series.
b. C₅H₁₀ has higher molecular mass, more surface area, more van der Waal’s forces of attraction, hence higher boiling point than C₄H₈.
c. C₃H₆ < C₄H₈ < C₅H₁₀

Question: (a) Name one gustatory receptor and one olfactory receptor present in human beings.
(b) Write a and b in the given flow chart of neuron through which information travels as an electrical impulse.
Dendrite → a → b→ End point of Neuron
Answer: (a) Tongue / Nose.
(b) a → Cell body, b → axon 

Question: Name two oxidising agents that are used to convert alcohols to acids. Distinguish between ethanol and ethanoic acid on the basis of (a) litmus test (b) reaction with NaHCO₃.
Answer : 
These two oxidising agents will convert alcohols to acids (i) Alkaline KMnO₄ (ii) Acidified K₂Cr₂O₇
a. Litmus test: Acetic acid turns blue litmus red but ethanol does not.
b. NaHCO₃ test: Acetic acid will give brisk effervescence due to evolution of CO₂ whereas ethanol will not react.

Question: The general formula of three compounds A, B and C is Cn (H2n . ‘B’ has highest boiling point and ‘C’ has lowest boiling point.
a. Mention the type of compounds A, B, C.
b. Which of these have minimum number of carbon atoms?
c. Name the homologous series to which A, B and C belong.
Answer : 
a. A, B, C are unsaturated compounds.
b. C has minimum number of carbon atoms..
c. They belong to alkene homologous series.

Question: Complete the following equations:
a. CH₃COOC₂H₅ + NaOH →
b. CH₃COOH + NaOH →
c. C₂H₅OH + CH3COOH → Conc.H₂SO₄
Answer : a. CH3COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
b. CH₃COOH + NaOH → CH₃COONa + H2O
c. C₂H₅OH + CH₃COOH  → Con.H₂SO₄ CH₃COOC₂H₅ + H₂O

Question: Draw the electron dot structure of ethyne. A mixture of ethyne and oxygen is burnt for welding. In your opinion, why cannot we use a mixture of ethyne and air for this purpose?
Answer : 
HC / CH, Ethyne,
Ethyne and oxygen will produce lot of heat on combustion needed for welding whereas ethyne and air will not produce enough heat needed for welding purposes.

Question: What are covalent compounds? Why are they different from ionic compounds? List three characteristic properties.
Answer : 
Those compounds in which bonds are formed by sharing of electrons are covalent compounds.
While ionic compounds are formed by complete transfer of electrons.    
  Covalent compounds                                                                     Ionic compounds
1. They have weak intermolecular forces of attraction.             They have strong intermolecular forces of attraction.
2. They have low melting and boiling points.                            They have high melting and boiling points.
3. They do not conduct electricity.                                            They conduct electricity in molten state or in aqueous solution.

Question: Complete the following reactions:

a. CH₃COOH + N₂CO₃ →
b. CH₄ + O₂ →
c. C₂H₅OH + Na →
Answer : 
a. 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
b. CH4 + 2O₂ → CO₂ + 2H₂O
c. 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

Question: Under which condition an oxidation reaction can be called as combustion reaction. Illustrate your answer with example.
Answer : 
When oxidation reaction produces heat as well as light it is called combustion reaction.
CH₄ + 2O₂ → CO₂ + 2H₂O + heat + light
It is oxidation as well as combustion reaction.

Question: a. Give chemical tests to detect the presence of (a) ethanol (b) ethanoic acid.
b. Why ethanoic acid is called glacial acetic acid?
Answer : 
(i) (a) Ethanol reacts with Na to liberate H₂ gas 
2CH₃CH₂OH + 2Na →  2CH₃CH₂ONa + H₂
(b) Ethanoic acid gives brisk effervescence of CO₂ with NaHCO₃
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂

(ii) It is because pure acetic acid (anhydrous) solidifies into solid crystals just below the room temperature at 16.7°C and look like glacier of snow.

Question: 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. It is due to tetravalency of carbon and property of catenation shown by carbon to maximum extent.
b. Air holes must be kept open fully so that complete combustion of fuel takes place producing blue flame.
c. Some of detergents are not bio¬degradable, they create water pollution.

Question: a. Why are most carbon compounds poor conductors of electricity?
b. Write the name and structure of a saturated compound in which carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.
Answer : 
a. It is because covalent compounds do not form ions, therefore, do not conduct electricity.
It has 18 single bonds.

 Question: a. What is meant by a functional group in an organic compound? Name the functional group present in
(1) CH₃CH₂OH
(2) CH₃COOH
b. State one point of difference between soap and synthetic detergent.
Answer : 
a. Functional group is an atom or group of atoms which determine chemical properties of organic compounds. (1) Alcohol, (2) Carboxylic acid.
a. Soaps do not work well with hard water as form insoluble scum whereas detergents work well with hard water.

Question: Explain giving reasons, why carbon can neither form C4+ cation nor C4- anion but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points.
Answer : Carbon cannot lose four electrons because high energy is needed to remove four electrons. It cannot gain 4 electrons because 6 protons cannot hold 10 electrons.
It can share 4 electrons to form covalent bonds.
Covalent compounds do not conduct electricity because these do not form ions. They have low melting and boiling points due to weak force of attraction between molecules.

Question: Why is homologous series of carbon compounds so called? Write the chemical formula of two consecutive members of any two homologous series and state the part of these compounds that determines their (a) physical and (b) chemical properties. 
Answer : Homologous means members of same family that is why series of carbon compounds having same functional group and similar properties is called homologous series.
Homologous series of alcohol.
CH₃OH Methanol
C₂H₅OH Ethanol 
CH₃— and C₂H₅— groups determine physical properties and —OH group determines chemical properties. Homologous series of aldehyde.
CH₃OH Ethanol
C₂H5OH Propanal
Here, CH₃—and C₂H₅— groups determine physical properties while —CHO group determines chemical properties.

 Question: Write any three physical properties and three uses of ethanol.
Answer : 
Properties
a. Ethanol has specific smell.
b. It is soluble in water.
c. It has burning taste.
Uses
a. It is used as solvent.
b. It is used as an antiseptic.
c. It is used in wine, beer, whisky, etc.
d. It is used for preparation of ethanoic acid, ethyl ethanoate (esters).

Question: The number of carbon compounds is more than those formed by all other elements put together. Justify the statement by giving two reasons.
Answer.
- Due to self linking ability of carbon/catenation
- Since carbon has a valency of four it can form bonds with four other atoms of carbon or atoms of some other mono-valent element.
- Due to small size of carbon it forms very strong and (or) stable bonds with other elements

Question: What are covalent compounds? Why are they different from ionic compounds? List their three characteristic properties. 
Answer. Those compounds which are formed by equal sharing of electrons are called covalent compounds.
They are different from ionic compounds since ionic compounds are formed by transfer of electrons from one atom to another.
Properties:
(i) They have low melting and boiling points.
(ii) They do not conduct electricity in molten state and in aqueous solution.
(iii) They are mostly insoluble in water but soluble in organic solvents except glucose, sugar, urea, ethyl
alcohol, etc.

Question: Compare the ability of catenation of carbon and silicon. Give reasons. 
Answer. Carbon shows catenation property to more extent than silicon. It is because C–C bond is stronger than Si–Si bond because carbon is smaller in size than silicon.

Question: Give a test that can be used to confirm the presence of carbon in a compound. With a valency of 4, how is carbon able to attain noble gas configuration in its compounds? 
Answer.
– Burn compound in air/ oxygen; Gas evolved turns lime water milky
– By sharing its four valence electrons with other elements.

Question: Carbon, a member of group 14, forms a large number of carbon compounds estimated to be about three million. Why is this property not exhibited by other elements of this group? Explain. 
Answer. Carbon shows the property of catenation.
It forms strong covalent bonds with other atoms of carbon forming long straight, branched and closed chain compounds.
Carbon is smallest in size in group 14 with tatravalency, it can form double as well as triple bonds,therefore, it can show property of catenation to maximum extent and forms 3 million compounds other elements cannot show property of catenation to this extent due to larger size form weaker covalent bond and cannot form double or triple bonds.