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NCERT Solutions For Class 8 Maths

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CBSE Chemsitry Notes For Class 11 Aliphatic Hydrocarbons Alkanes

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Class 11 Chemistry Hydrocarbons Aliphatic Hydrocarbons Alkanes

Open-chain saturated hydrocarbons are referred to as alkanes. At ordinary temperature and pressure, they generally do not show any affinity towards most of the reagents such as acids, bases, oxidizing, and reducing agents and because of this inertness, they are called paraffin (Latin: param = litde, affinis= affinity).

⇒ Each C-atom present in an alkane molecule is sp³ -hybridized. Four σ -bonds formed by each sp³ -hybridized carbon are directed towards the comers of a regular tetrahedron.

⇒  Thus, alkanes have a tetrahedral structure around each carbon atom. The molecular formula of alkanes is CnH2n + 2 [where n = 1, 2, ].

⇒  Their general formula is RH (R: alkyl group).

1. Nomenclature of alkanes

The nomenclature of alkanes according to the IUPAC system has been thoroughly Here, only the trivial names of the isomers of butane and pentane and the IUPAC names of some higher alkanes are mentioned

CBSE Chemsitry Notes For Class 11 Hydrocarbons IUPAC Names Of Some Higher Alkanes

2. Structure of alkanes

Alkanes contain only carbon-carbon and carbon-hydrogen single bonds. They have the following structural
characteristics:

  • Each C-atom is sp³ -hybridized. Four sp³ -hybrid orbitals are directed towards the comers of a regular tetrahedron. The carbon atom lies at the center of the tetrahedron.
  • All C—C and C—H bonds are strong sigma bonds. Each C —C cr -bond is formed as a result of the axial overlapping of two sp³ orbitals, one from each carbon atom, and each C—H bond is formed by the axial overlapping of one sp³ orbital of carbon with the s -orbital of hydrogen.
  • C—C and C—H bond lengths are 1.54A & 1.12A respectively. lv] All bond angles in alkanes (C —C —C, C —C —H, and H—C—H) have a value of 109°28′. Thus, alkanes possess tetrahedral structure

CBSE Chemsitry Notes For Class 11 Hydrocarbons Structure Of Ethane

  • Carbon atoms in an alkane molecule having three or more carbon atoms do not lie along a straight line. Instead, they form a zig-zag pattern. This is because each carbon atom is sp³ -hybridized and naturally the C—C— C bond angle is 109°28′ instead of 180°. It becomes clear from the structure of propane

CBSE Chemsitry Notes For Class 11 Hydrocarbons Structure Of Propane

  • C—C and C—H bond dissociation enthalpies are 83kcal -mol-1 and 99 kcal-mol-1 respectively

CBSE Chemsitry Notes For Class 11 Hydrocarbons Benzenoid Three And Two Dimensional Representation

3. Structural isomerism in alkanes

Alkanes (except methane, ethane, and propane) exhibit chain isomerism, a type of structural isomerism. This type of isomerism arises due to the difference like the carbon chain or the skeleton of the carbon atoms.

Example:

1. The two chain isomers having molecular formula (C4H10) are n-butane and isobutane. If a 1° or 2° H atom of a propane molecule is replaced by a methyl group, then these two isomers are formed.

CBSE Chemsitry Notes For Class 11 Hydrocarbons Two Chain Isomers of Molecular N butane And Isobutane

Example:

2. Three chain isomers of molecular formula C5H12 are n -pentane (CH3CH2CH2CH2CH3), isopentane [(CH3)2CHCH2CH3] and neopentane [(CH3)4C].

CBSE Chemsitry Notes For Class 11 Hydrocarbons Three Chain Form Of Isomers

3. These isomers are formed on the replacement of different H -atoms of n-butane and isobutane by methyl group

4 . Five chain isomers have molecular formula C6H14 and these by obtained by replacement of different types of H-atoms of n-pentane, isopentane, and neopentane by a methyl group.

These are as follows:

CBSE Chemsitry Notes For Class 11 Hydrocarbons Methyl Group

4. Conformational isomerism in alkanes

Conformational isomerism definition:

Electronic distribution of the sigma molecular orbital of a C—C bond is cylindrically symmetrical around the internuclear axis and as this is not disturbed due to rotation about its axis, free rotation about the C—C single bond is possible. An infinite number of spatial arrangements of atoms that result through rotation about a single bond are called conformations or conformational isomers or rotational isomers or simply conformers or rotamers and the phenomenon is called conformational isomerism.

The difference in potential energy between the most stable conformation and the conformation under consideration is called the conformational energy of the given conformation.It is to be noted that the rotation around a C—C single bond is not completely free.

It is hindered by a very small energy barrier of 1-20kl-mol-1due to very weak repulsive interaction between the electron clouds of different σ -bonds. Such repulsive interaction is called torsional strain.

Conformations are three-dimensional.

These are generally represented in paper by three projection formulae:

Flying wedge formula, sawhorse projection formula and Newman projection formula.

Conformations of ethane:

A molecule of ethane (CH3—CH3) contains a carbon-carbon single bond (σ -bond) and each carbon atom is attached to three hydrogen atoms. The two —CH3 groups can rotate freely around the C—C bond axis.

Rotation of one carbon atom keeping the other fixed results into an infinite number of spatial arrangements of hydrogen atoms attached to the rotating carbon atom concerning the hydrogen atoms attached to a fixed carbon atom.

  • These are called conformational isomers or conformations or conformers.
  • Thus, there are an infinite number of conformations of ethane. However, there are two extreme cases. The conformation in which the hydrogen atoms attached to two carbons are as close together as possible.
  • In which the dihedral angle between the two nearest C —H bonds of two — CH3 groups is zero, is called the eclipsed conformation.
  • The conformation in which the hydrogen atoms are as far apart as possible, i.e., the dihedral angle between two C —H bonds is 60° is called the staggered conformation.
  • The eclipsed conformation suffers from maximum torsional strain whereas in staggered conformation this strain is minimal.
  • So, the eclipsed conformation is much less stable than the staggered conformation.
  • Any other intermediate conformation i.e., the conformation in which the dihedral angle is between 0-60°, is called the skew conformation.

Its stability is in between the two extreme conformations. Therefore, the order of stability of these three conformations is:

Staggered > skew > eclipsed.

It is to be noted that in all these conformations, the bond angles and the bond lengths remain the same.

Saturated hydrocarbons containing more than two carbon atoms have different conformations. However, as there is only one carbon atom in methane, it does not exist in the above-mentioned conformations. The eclipsed and the staggered conformations of ethane can be represented by the flying wedge formula, sawhorse projection formula and

Newman projection formula is as follows:

1. Flying wedge formula:

In this representation, the two bonds attached to a carbon atom are shown in the plane of the paper and of the other two, one is shown above the plane and another below the plane. The bonds that are in the plane are shown by normal lines (—) but the bond

Above the plane is shown by a solid wedge ( —) bond below the plane is shown by a hashed wedge

CBSE Chemsitry Notes For Class 11 Aliphatic Hydrocarbons Alkanes

2. Sawhorse projection formula:

In this projection, the molecule is viewed along the molecular axis. It is then projected on paper by drawing the central C —C bond as a somewhat elongated line. The upper end of the line is slightly tilted towards the righthand side. The front carbon is shown at the lower end of the line, whereas the rear carbon is shown at the upper end.

Each carbon has three lines attached to it corresponding to three H -atoms. The lines are inclined at a 120° angle to each other.

CBSE Chemsitry Notes For Class 11 Hydrocarbons Sawhorse Conformation Formula

3. Newman projection formula:

In this projection, the molecule is viewed along the C —C bond. The C-atom nearer to the eye of the viewer (i.e., the front carbon) is represented by a point and the three H-atoms attached to the front C-atom are shown by the three lines drawn at an angle of 120° to each other. The C-atom situated farther from the eye of the viewer (i.e., the rear carbon) is represented by a circle, and the three hydrogen atoms attached to it are represented by three shorter lines drawn at an angle of 120° to each other.

Eclipsed and staggered conformations of ethane in I H H terms of the

Newman projection formula (along with dihedral angles, ) are shown below:

CBSE Chemsitry Notes For Class 11 Hydrocarbons Eclipsed And Staggered Conformation

The energy barrier between two extreme conformations is tiny and so, the rotation of two —CH3 groups takes place extremely rapidly. Due to this, it is not possible to separate the conformations of ethane. However, at any moment, the majority of ethane molecules exist in the staggered  conformation of minimum energy {i.e., maximum stability)

The eclipsed conformation is least stable because hydrogens and bonding pairs of electrons eclipsed C —H bonds involving adjacent C-atoms are very close to each other causing maximum repulsion. The staggered conformation is most stable because the hydrogens and bonding pairs of electrons of each pair of C —H bonds involving adjacent C-atoms are at a maximum distance. This causes minimum electronic as well as steric repulsion

The potential energy of the molecule is minimal for staggered conformation. It increases with rotation and reaches a maximum at eclipsed conformation. Experimentally, it has been found that the staggered conformation of ethane is 2.8 kcal-mol-1 more stable than the eclipsed conformation. (Eeclipsed  eclipsed –  Estaggered   = 2.8 kcal-mol-1 ).

Therefore, rotation about C—C bond is not completely free. However, this energy barrier is not large enough to prevent rotation at room temperature as collisions between the molecules supply sufficient kinetic energy to overcome this energy barrier

CBSE Chemsitry Notes For Class 11 Hydrocarbons Eclipsed And Staggered Conformation Potential Energy

Dihedral angle:

The dihedral angle (Φ) is the angle between the X—C—C and the C—C—Y plane of X—C—C—Y unit in a molecule. In ethane, it is the

CBSE Chemsitry Notes For Class 11 Hydrocarbons Dehydration Angle

The angle between the H—1C— 2C plane and 1C—2C—H plane, 1 2 i.e., it is the angle between the 2C—H bond and the C—H bond in the Newman projection formula. It is also called the angle of torsion.

Conformations of propane (1CH3– 2CH2–3CH3):

In propane molecules, both C1—C2 & C2—C3 bonds are equivalent. An infinite number of conformations of propane can be obtained as a result of rotation about the C1—C2 (or C2—C3) bond. The two extreme conformations are the eclipsed conformation (I) and the staggered conformation

The staggered conformation is more stable than the eclipsed conformation by 3.4 kcal-mol-1

Conformations of n-butane (CH3-CH2-CH2-CH3):

n-butane contains two kinds of C —C bonds. So, conformations likely to be generated depend on that particular C —C bond around which C-atoms are made to rotate

CBSE Chemsitry Notes For Class 11 Hydrocarbons Conformations Of n Butane

1. Rotation about the C1—C2 bond:

Keeping C1 fixed, when C2 is rotated around the C1—C2 bond axis, infinite numbers of conformations are obtained. Among these, twoprincipal conformations are eclipsed (I) and staggered (II) conformations.

Their order of stability is:

Staggered > eclipsed, i.e., molecules of n-butane spend most of their time in staggered conformation (II).

2. Rotation about the C2-C3 bond:

An infinite number of conformations are possible if C3 is made to rotate around C2 — C3 bond axis, keeping C2 fixed.

Among these, the four chief conformations are:

  1. Anti-staggered (1)
  2. Gauchestaggered (3)
  3. Eclipsed (2)
  4. Fully eclipsed (4).

In anti-staggered conformation, the two —CH3 groups exist anti to each other, i.e., they are oriented at an angle of 180° (Φ = 180°). In the gauche-staggered conformation, the two —CH3 groups make an angle of 60° with each other (Φ = 60°). In the eclipsed conformation, the two pairs of —CH3 and H and one pair of H -atoms are in direct opposition, while in the fully eclipsed conformation, the two pairs of H-atoms and one pair of CH3 groups are in direct opposition.

The order of their stability:

1 >3 > 2 > 4, i.e., the molecules of n-butane pass most of their time in anti-staggered conformation (I).

Their Newman projection formulae are shown below:

CBSE Chemsitry Notes For Class 11 Hydrocarbons Newman Projection Formulae

The most stable and least stable conformations of n-butane are anti-staggered and fully eclipsed conformations respectively. The angular distance between two similar bonds in the anti-staggered conformation is maximum (180°). Thus, repulsion between electrons of such a bond pair is minimal.

Again, two —CH3 groups are located farthest from each other so, no steric hindrance or steric strain acts between them. On the other hand, the angular distance between two similar bonds in the fully eclipsed conformation is minimum (0°). Thus, the repulsion between electrons of each bond pair is maximum.

Again, two —CH3 groups are in direct opposition and hence there occurs severe steric strain involving these two CH3 groups. For this reason, anti-staggered conformation is the most stable while fully eclipsed conformation is the least stable conformation of  n-butane

The potential energy changes during rotation about the C2—C3 bond of n-butane is shown in the following diagram

CBSE Chemsitry Notes For Class 11 Hydrocarbons The Potential Energy Changes Rotation Of Bond Of n Butane

CBSE Class 12 Maths Important Question and Answers

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NCERT Notes For Class 6 Maths

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NCERT Notes For Class 6 Maths

NCERT Class 6 Science Chapter 4 Getting To Know Plants Multiple Choice Questions

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NCERT Class 6 Science Chapter 4 Getting To Know Plants Multiple Choice Questions

Question 1. The plant which cannot be classified as a shrub is

  1. Jasmine
  2. Bougainvillea
  3. Carrot
  4. Lemon

Answer: 3. Carrot

Question 2. Which one of the following best describes the characteristics of a tree?

  1. Jasmine
  2. Bougainvillea
  3. Carrot
  4. Cotton

Answer: 2. Bougainvillea

Read and Learn More NCERT Class 6 Science MCQs

Question 3. Which of the following is the correct match between the characteristics of the stem and the category of the plant?

  1. Weak stem which cannot stand upright- creeper
  2. Green tender stem-shrub
  3. Thick, hard stem with branching near the base-tree
  4. Thick, hard stem with brandies high on the plant-herb

Answer: 1. Weak stem which cannot stand upright- creeper

Question 4. The picture shows a pumpkin. The spreading stems shown to indicate that a pumpkin should be classified as competency

Class 6 Science Chapter 4 Getting To Know Plants The spreding stems a pumpkin

  1. Herb
  2. Shru
  3. Creeper
  4. Tree

Answer: 3. Creeper

Question 5. The part of the plant which grows towards light and it also transports water, minerals and food.

  1. Stem
  2. Roots
  3. Leaf
  4. Flower

Answer: 1. Stem

Question 6. Which of the following is not the primary function of the stem?

  1. Conduction of water
  2. Photosynthesis
  3. Formation of branches
  4. Bears flowers and fruits

Answer: 2. Photosynthesis

Question 7. Which of the following is not a correct match?

  1. Petiole: attaches the leaf to the stem
  2. Lamina: green flat part of the leaf
  3. Margin: gives shape to the leaf
  4. Veins: transpiration

Answer: 4. Veins: transpiration

Question 8. Which of the following combinations of features would you observe in grass?

  1. Parallel venation and fibrous root
  2. Parallel venation and tap root
  3. Reticulate venation and fibrous root
  4. Reticulate venation and tap root

Answer: 1. Parallel venation and fibrous root

Question 9. Read the following sentences about photosynthesis.

  1. Sunlight, carbon dioxide, chlorophyll and water are necessary.
  2. Oxygen is absorbed.
  3. Leaves carry out photosynthesis.
  4. Proteins are made during photosynthesis.

Choose the correct pair of sentences that is true to photosynthesis

  1. 3 And 4
  2. 1 And 3
  3. 2 And 4
  4. 1 And 4

Answer: 2. 1 And 3

Question 10. Sarita pulled a herb out of the soil and observed that a plant part came out with it. Rohlni was watching the activity and saw some hair-like structures coming out from that part what could be the plant part?

  1. Flower
  2. Leaf
  3. Root
  4. Stem

Answer: 3. Root

Question 11. Which of the following plants does not have a tap root?

  1. Marigold
  2. Mango
  3. Maize
  4. Turnip

Answer: 3. Maize

NCERT Class 6 Science Chapter 4 Getting To Know Plants MCQs

Question 12. Which part of the plant grows in the soil?

  1. Stem
  2. Leaf
  3. Root
  4. Seed

Answer: 3. Root

Question 13. In the given diagram which part of the flower contains yellow powdery substances?

Class 6 Science Chapter 4 Getting To Know Plants Parts Of Flowers

  1. Ovary
  2. Filament
  3. Style
  4. Anther

Answer: 2. Filament

Question 14. Reproductive parts what characteristics would that plant portion have?

  1. Presence of stomata
  2. Presence of stamens and pistil
  3. Presence of midrib
  4. Presence of root hairs.

Answer: 2. Presence of stamens and pistil

Question 15. The male parts of the flower are called

  1. Pistil
  2. Carpel
  3. Stamen
  4. Style

Answer: 3. Stamen

Question 16. Which one of the following statements is incorrect?

  1. Leaves can only make food when there is light
  2. Male flowers will develop into fruits
  3. Roots hold the plant firmly to the ground
  4. Plants need air, water and sunlight to grow

Answer: 2. Male flowers will develop into fruits

Question 17. Which of the following terms constitutes the female part of the flower?

  1. Sepals, petals and stamen
  2. Stigma, style and ovary
  3. Ovary, stamen and stigma
  4. Ovary, style and stamen

Answer: 2. Stigma, style and ovary

Question 18. The underground plant part which anchors the plant to the soil is

  1. Stem
  2. Internode
  3. Leaves
  4. Roots

Answer: 2. Internode

Question 2. What part of the plant do we eat as food in turnip?

  1. Roots
  2. Stem
  3. Flower
  4. Trunk

Answer: 1. Roots

Question 3. Taproot is found in

  1. Onion
  2. Marigold
  3. Millet
  4. Wheat

Answer: 2. Marigold

Question 4. Which of the following plants does not have a tap root?

  1. Mustard
  2. Maize
  3. Tulsi
  4. Balsam

Answer: 2. Maize

Question 5. The lowermost and swollen part of the pistil is catted

  1. Ovule
  2. Ovary
  3. Style
  4. Filament

Answer: 2. Ovary.

NCERT Class 6 Science Chapter 5 Body Movement Multiple Choice Questions

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NCERT Class 6 Science Chapter 5 Body Movement Multiple-Choice Questions

Question 1. Which of the following parts of our body help us in movement?

  1. Bones
  2. Skin
  3. Muscles
  4. Organs

Choose the correct answer from the option given below.

  1. 1 And 3
  2. 2 And 4
  3. 1 And 4
  4. 2 And 3

Answer: 1. 1 And 3

Question 2. Which of the following joints is immovable?

  1. Shoulder and arm
  2. Knee and joint
  3. Upper jaw and skull
  4. Lower jaw and upper jaw

Answer: 3. Upper jaw and skull

Read and Learn More NCERT Class 6 Science MCQs

Question 3. Human skeleton comprises

  1. Skull and backbone
  2. Ribs and breastbone
  3. Shoulder and hip bone
  4. All of these

Answer: 4. All of these

Question 4. How does the structure of the skeleton system support the body?

  1. It protects the outer skin of the body from any injury
  2. It provides a framework that gives shape to the body
  3. It provides the site for storing all the nutrients in the body
  4. It allows free movement of all the bones during locomotion

Answer: 2. It provides a framework that gives shape to the body

Question 5. The organ that protects the main nerve cord is

  1. Skull
  2. Backbone
  3. Breast bone
  4. Chest bone

Answer: 2. Backbone

NCERT Class 6 Science Chapter 5 Body Movement Multiple Choice Questions

Question 6. The bone formed from the collarbone and shoulder blade is

  1. Shoulder bone
  2. Chest bones
  3. Hand bones
  4. Backbone

Answer: 1. Shoulder bone

Question 7. Cartilages are human body parts that are attached to the skeleton. They are not as hard as bones, but they break when hit badly. Which of these human body parts is made up of cartilage?

  1. Nail
  2. Hair
  3. Nose
  4. Eyelid

Answer: 3. Nose

Question 8. How many muscles work together to move a bone?

  1. One
  2. Two
  3. Three
  4. Pour

Answer: 2. Two

Question 9. Muscles work in pairs. They contract and relax simultaneously. How does this help an individual?

  1. It assists in the formation of the bones
  2. It prevents any injury to the internal organs
  3. It allows the movement of bones at the joints
  4. It helps in the absorption of nutrients in the body

Answer: 3. It allows the movement of bones at the joints

Question 10. Which of the following organisms does not have both muscles and skeletons for movement?

  1. Dog
  2. Snail
  3. Earthworm
  4. Human being

Answer: 3. Earthworm

Question 11. Snail moves with the help of its

  1. Shell
  2. Bone
  3. Muscular foot
  4. Whole body

Answer: 3. Muscular foot

Question 12. In cockroaches, the body parts helping in movement include

  1. Three pairs of legs and two pairs of wings
  2. Two pairs of legs and two pairs of wings
  3. Two pairs of legs and three pairs of wings
  4. None of the above

Answer: 1. Three pairs of legs and two pairs of wings

Question 13. Which one of the following are the characteristics of birds?

  1. Strong muscles
  2. Light bones
  3. Hollow bones
  4. All of these

Answer: 4. All of these

Question 14. Both cockroaches and birds have wings to fly in the air. However, only cockroaches can climb on the walls. What is the likely reason for this?

  1. They lack muscles
  2. They have hollow bones
  3. They have strong and broad wings
  4. They have three pairs of modified legs

Answer: 4. They have three pairs of modified legs

Question 15. Which of these represents one of the reasons that enable birds and not humans to fly?

  1. They have long bones
  2. They have extra forelimbs
  3. They have strong hind bones
  4. They have hollow and light bones

Answer: 4. They have hollow and light bones

Question 16. Fishes swim by

  1. Forming loops alternately on two sides of the body
  2. Forming loops on a single side
  3. Somersaulting
  4. Alternate dipping and coming up

Answer: 1. Forming loops alternately on two sides of the body

Question 17. Underwater divers wear fin-like flippers on their feet to

  1. Swim easily in water
  2. Look like a fish
  3. Walk on the water’s surface
  4. Walk over the bottom of the sea (sea bed)

Answer: 1. Swim easily in water

Question 18. How can fishes flow around easily in the water?

  1. Due to small-sized body
  2. Due to a streamlined body
  3. Due to the presence of thin skin
  4. Due to the presence ofscales on their body

Answer: 2. Due to a streamlined body

Question 19. The table describes the body shape of four animals.

Class 6 Science Chapter 5 Body Movements The Body Shape Of Four Animals

Which animal is likely to swim the fastest in water?

  1. Animal p
  2. Animal q
  3. Animal r
  4. Animal s

Answer: 2. Animal q

Question 20. The joint in the skull is a

  1. Gliding joint
  2. Ball and socket joint
  3. Fixed joint
  4. Hinge joint

Answer: 3. Ball and socket joint

Question 21. Which of the following is not correct regarding the human skeleton?

  1. All the bones are connected by joints
  2. Bones are made of calcium
  3. Bones can move by themselves
  4. Cartilage is also a part of the skeleton

Answer: 3. Bones can move by themselves

Question 23. The skeleton of the human body is made up of

  1. Bones
  2. Cartilage
  3. Both 1 and 2
  4. Muscles

Answer: 3. Both 1 and 2

Question 24. Which of the following is not a type of movable joint?

  1. Pivot joint
  2. Fixed joint
  3. Ball and socket joint
  4. Hinge joint

Answer: 2. Fixed joint

Question 25. How many bones are there in the human backbone?

  1. 31
  2. 33
  3. 32
  4. 35

Answer: 2. 33

NCERT Class 6 Science Multiple Choice Questions

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NCERT Class 6 Science Chapter 3 Separation Of Substances Multiple Choice Questions

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Separation Of Substances Multiple Choice Questions

Question 1. Paheli bought some vegetables such as French beans, ladyfinger, green chilies, brinjals, and potatoes all mixed in a bag. Which of the following methods of separation would be most appropriate for her to separate them?

  1. Winnowing
  2. Sieving
  3. Threshing
  4. Handpicking

Answer: 4. Handpicking

Question 2. Boojho’s grandmother is suffering from diabetes. Her doctor advised her to take ‘lassi’ with less fat content. Which of the following methods would be most appropriate for Boojho to prepare it?

  1. Filtration
  2. Decantation
  3. Churning
  4. Winnowing

Answer: 3. Churning

Read and Learn More NCERT Class 6 Science MCQs

Question 3. Which of the following methods would be most appropriate to separate grains from bundles of stalks?

  1. Handpicking
  2. Winnowing
  3. Sieving
  4. Threshing

Answer: 4. Threshing

Question 4. Which method is used for separating heavier and lighter components by blowing air?

  1. Sieving
  2. Threshing
  3. Winnowing
  4. Sedimentation

Answer: 3. Winnowing

Question 5. Four mixtures are given below.

  1. Kidney beans and chickpeas
  2. Pulses and rice
  3. Rice flakes and corn
  4. Potato wafers and biscuits

Which of these can be separated by the method of winnowing?

  1. 1 And 2
  2. 2 And 3
  3. 1 And 3
  4. 3 And 4

Answer: 4. 3 And 4

NCERT Class 6 Science Chapter 3 Separtion Of Substances MCQs

Question 6. While preparing chapatis, paheli found that the flour to be used was mixed with wheat grains. Which of the following is the most suitable method to separate the grains from the flour?

  1. Threshing
  2. Sieving
  3. Winnowing
  4. Filtration

Answer: 2. Sieving

Question 7. The easiest separating method which can be used to separate wheat bran from flour is

  1. Handpicking
  2. Sieving
  3. Evaporation
  4. Filtration

Answer: 2. Sieving

Question 8. A bottle contains either salt or chalk. What process would you use to identify them?

  1. Sedimentation
  2. Evaporation
  3. Winnowing
  4. Sieving

Answer: 1. Sedimentation

Question 9. You might have observed the preparation of ghee from butter and cream at home. Which method(s) can be used to separate ghee from the residue?

  1. Evaporation
  2. Decantation
  3. Filtration
  4. Churning

Which of the following combinations is the correct answer?

  1. 1 And 2
  2. 2 And 3
  3. 2 And 4
  4. Only 4

Answer: 2. 2 And 3

Question 10. Tea leaves are separated with a strainer while pouring tea.  What property of tea leaves is used to separate them from the tea?

Class 6 Science Chapter 3 Separation Of Substances Tea leaves are separted with a strainer, while pouring tea

  1. Size
  2. Mass
  3. Shape
  4. Thickness

Answer: 1. Size

Question 11. Which of the following mixtures would you be able to separate using the method of filtration?

  1. Oil in water
  2. Cornflakes in milk
  3. Salt in water
  4. Sugar in milk

Answer: 2. Cornflakes in milk

Question 12. Which of the following processes is used to remove the pulp from the juice before drinking?

  1. Sedimentation
  2. Hand-picking
  3. Decantation
  4. Filtration

Answer: 4. Filtration

Question 13. The ponds and other water bodies dry up at a faster rate during summers by the process known as

  1. Evaporation
  2. Condensation
  3. Decantation
  4. Distillation

Answer: 1. Evaporation

Question 14. In the activity, a teacher dissolved a small amount of solid copper sulfate in a tumbler half-filled with water. Which method would you use to get back solid copper sulfate from the solution?

  1. Decantation
  2. Evaporation
  3. Sedimentation
  4. Condensation

Answer: 2. Evaporation

Question 15. During summer, boojho carries water in a transparent plastic bottle to his school. One day, he left his bottle in the school. The bottle still had some water left in it. The next day, he observed some water droplets on the inner surface of the empty portion of the bottle. These droplets of water were formed due to

  1. Boiling and condensation
  2. Evaporation and saturation
  3. Evaporation and condensation
  4. Condensation and saturation

Answer: 3. Evaporation and saturation

Question 16. A student has a solution of salt, sand, and water. Which option explains the processes required to separate the salt and sand from water?

  1. Evaporation to remove sand, filtration to obtain salt
  2. Filtration to remove sand, evaporation to obtain salt
  3. Filtration to remove sand, sedimentation to obtain salts
  4. Sedimentation to remove sand, filtration to obtain salt

Answer: 2. Filtration to remove sand, evaporation to obtain salt

Question 17. Paheli asked for a glass of water from Boohoo. He gave her a glass of ice-cold water. Paheli observed some water droplets on the outer surface of the glass and asked Boojho, how these droplets of water were formed. Which of the following should be Boojho’s answer?

  1. Evaporation of water from the glass
  2. Water that seeped out from the glass
  3. Evaporation of atmospheric water vapor
  4. Condensation of atmospheric water vapor

Answer: 4. Condensation of atmospheric water vapor

Question 18. Which of the following can dissolve in water?

  1. Iron dust
  2. Oil
  3. Chalkdust
  4. Salt

Answer: 4. Salt

Question 19. A salt solution gets saturated when a student mixes 10 gms of salt in 60ml of water in a beaker. The student further added logos of salt in the solution that does not dissolve in water. The student adds 20ml of water to a beaker and observes some of the salt is dissolved.  The amount of water needed to dissolve the remaining salt is?

  1. 5 Mb
  2. 10Ml
  3. 20 Ml.
  4. 40 Ml

Answer: 4. 40 Ml

Question 20. A student did the following activity to separate the constituents of a mixture as shown below

Separation Of Substances water,sand,glass

What could have been the mixture?

  1. Water + sand + glass
  2. Oxygen + water + salt
  3. Stones + rice + water
  4. Sand + sugar + water

Answer: 4. Sand + sugar + water

Question 21. A student takes some cold water in a beaker and dissolves two tablespoons of salt in it. When the student adds one more tablespoon of salt, it gets settled at the bottom of the beaker. The student warms the water and observes that the salt disappears. What can be the reason for this observation?

  1. Heat increases the solubility of water
  2. Heat evaporates the excess salt in solution
  3. After heating the solution becomes saturated
  4. Two tablespoons of salt make the solution unsaturated

Answer: 1. Heat increases the solubility of water

Question 22. Raman had kept three things, salt, and rice grains separately to do some experiments.  Somehow everything got mixed up. Choose the correct option that contains a correct sequence of methods which is used to separate all these things again.

  1. Add water → evaporation → sieving → sedimentation
  2. Add water → sedimentation → sieving → evaporation
  3. Add water → sieving → evaporation → sedimentation
  4. Sieving → add water → sedimentation evaporation

Answer: 4. Sieving → add water → sedimentation evaporation

Question 21. Choose the correct statement about decantation from the following.

  1. The process of settling down heavier, insoluble particles in a mixture
  2. The process of changing a solid into a vapor state
  3. Separating insoluble solids from a liquid using filter paper
  4. The process of transferring the clear liquid without disturbing the sediments

Answer: 4. The process of transferring the clear liquid without disturbing the sediments

Question 22. The property which forms the basis of sieving is a difference of components in

  1. Size
  2. Color
  3. Shape
  4. Weight

Answer: 1. Size

Question 3. The first process after harvesting is

  1. Reaping
  2. Threshing
  3. Sieving
  4. Winnowing

Answer: 2. Threshing

Question 4. Common salt is recovered from seawater by the process of

  1. Filtration
  2. Evaporation
  3. Sublimation
  4. Decantation

Answer: 2. Evaporation

Question 5. Threshing is done by

  1. Wilting
  2. Bullocks
  3. Machines
  4. All of these

Answer: 4. All of these

NCERT Class 6 Science Chapter 2 Sorting Materials Into Groups Multiple Choice Questions

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Sorting Materials Into Groups Multiple Choice Questions

Question 1. Which object is commonly made up of plastic?

  1. House gate
  2. Sleeping cot
  3. Cooking vessel
  4. Water bottle

Answer: 4. Water bottle

Question 2. Neeraj spilt some water on the floor. He cleaned the floor using a mop. Which material is best suited for making the mop?

  1. Iron scrubber
  2. Cotton cloth
  3. Plastic sheet
  4. Copper sheet

Answer: 2. Cotton cloth

Question 3. Which among the following are commonly used for making a safety pin?

  1. Wood and glass
  2. Plastic and glass
  3. Leather and plastic
  4. Steel and plastic

Answer: 4. Steel and plastic

Read and Learn More NCERT Class 6 Science MCQs

NCERT Class 6 Science Chapter 2 Sorting Materials Into Groups MCQs

Question 4. Find the odd one out from the following.

  1. Tawa
  2. Spade
  3. Pressure cooker
  4. Eraser

Answer: 4. Eraser

Question 5. Rakesh collected spoons made up of plastic, metal, glass and wood. Which of the following observations regarding each will be correct?

  1. Glass spoon will not break if dropped on the floor
  2. A wooden spoon will let liquid pass through it
  3. Plastic spoons will deform in hot temperature
  4. A metallic spoon can easily bend with pressure

Answer: 5. Metallic spoon can easily bend with pressure

Question 6. The picture shows two hollow pipes. One pipe is made up of copper and the other is made up of plastic.

Sorting Materials Into Groups The Two Hallow Pipes

Which of the following will help to identify the pipe made up of copper?

  1. Place the pipes in water and check if they absorb water
  2. Rub the pipes with sandpaper and check if they appear shiny
  3. Hold the pipes under a glowing bulb and check if they produce shadows
  4. Bring the pipes near a magnet and check if they are attracted by the magnet

Answer: 4. Bring the pipes near a magnet and check if they are attracted by the magnet

Question 7. An iron nail is kept in each of the following liquids. In which case would it lose its shine and appear dull?

  1. Mustard oil
  2. Soft drink
  3. Coconut oil
  4. Kerosene

Answer: 4. Kerosene

Question 8. Which of the following materials is not lustrous?

  1. Gold
  2. Silver
  3. Wood
  4. Diamond

Answer: 3. Wood

Question 9. The table shows objects sorted into two groups.

Sorting Materials Into Groups The objects between papers and metal

Which property was used to sort the objects into two groups?

  1. Hard/soft
  2. Shiny/dull
  3. Transparent/opaque
  4. Water soluble/water insoluble

Answer: 1. Hard/soft

Question 10. Arrange the following objects in order from hardest to softest.

  1. Rubber ball
  2. Cricket ball
  3. Stone
  4. Cotton ball

The correct order would be

  1. 1,2, 3, 4
  2. 4, 1,2,3
  3. 2,1,3,4
  4. 3, 2, 1,4

Answer: 4. 3, 2, 1,4

Question 11. Which of the following materials is rough?

  1. Sheet of glass
  2. Steel
  3. Stone
  4. Rubber

Answer: 3. Stone

Question 12. Pick one material from the following which is completely soluble in water.

  1. Chalk powder
  2. Tea leaves
  3. Glucose
  4. Sawdust

Answer: 3. Glucose

Question 13. Liquids that mix completely are called

  1. Volatile
  2. Immiscible
  3. Miscible
  4. Solution

Answer: 3. Miscible

Question 14. Oil floats on water. This is because

  1. It is denser than water
  2. It is less dense than water
  3. It is soluble in water
  4. Both have equal density

Answer: 2. It is less dense than water

Question 15. Rajiv dropped a silver and a gold coin each in a jar of water.

Sorting Materials Into Groups Rajiv Dropped A Silver And A Gold Coin Each In A Jar Of Water

Which question can be answered from the activity?

  1. Do gold and silver coins float on water?
  2. Is the gold coin harder than the silver coin?
  3. Is the gold coin heavier than the silver coin?
  4. Do gold and silver coins change size in water?

Answer:  1. Do gold and silver coins float on water?

Question 16. A coin, a sheet of paper and a gold ring were dropped in a glass of water. Which of these will sink and which will float?

  1. Coin and gold ring will float, while a sheet of paper will sink
  2. The coin will float, while the gold ring and sheet of paper will sink
  3. Sheet of paper will float, while gold rings and coins will sink
  4. The coin, gold ring and sheet of paper would all sink down

Answer: 3. The Sheet of paper will float, while the gold ring and coin will sink

Question 17. Which pair of substances among the following would float in a tumbler half-filled with water?

  1. Cotton thread, thermocol
  2. Feather, plastic ball
  3. Pin, oil drops
  4. Rubber band, coin

Answer: 2. Feather, plastic ball

Question 18. You are provided with the following materials

  1. Magnifying glass
  2. Mirror
  3. Stainless steel plate
  4. Glass tumbler

Answer: 3. Stainless steel plate

Question 19. Which of the above materials will you identify as transparent?

  1. 1 and 2
  2. 1 and 3
  3. 1 and 4
  4. 3 and 4

Answer: 1. 1 and 2

Question 20. Which type of the following materials is used for making the front glass (windscreen) of a car?

  1. Transparent
  2. Translucent
  3. Opaque
  4. All of these

Answer: 3. Translucent

Question 20. While doing an activity in class, the teacher asked Paheli to hand a translucent material. Which among the following materials will Paheli pick and give to her teacher?

  1. Glass tumbler
  2. Mirror
  3. Muslin cloth
  4. Aluminium foil

Answer: 3. Glass tumbler

Question 21. Which of these is a translucent object?

  1. An iron plate
  2. A glass sheet
  3. A concrete slab
  4. A sheet of tissue paper

Answer: 4. A sheet of tissue paper

Question 22. Boojho found a bag containing the following materials

  1. Mirror
  2. Paper stained with oil
  3. Magnet
  4. Glass spectacles

Help boojho in finding out the material(s) which is/are opaque.

  1. Only 1
  2. Only 4
  3. 1 and 3
  4. 2 and 4

Answer: 3. 1 and 3

Question 23. You are provided with a cardboard, a piece of glass, ice and a sheet of steel. Which of the following is the correct observation about the above materials?

  1. Only ice is opaque
  2. Only piece of glass is transparent
  3. Cardboard is translucent
  4. Ice and pieces of glass are transparent

Answer: 4. Ice and pieces of glass are transparent

Question 24. Glass can be made opaque by

  1. Spreading oil on it
  2. Spreading water on it
  3. Painting one side of it
  4. Pasting a thin sheet of paper on one side of it

Answer: 3. Painting one side of it

Question 25. Which of the following statements is not true?

  1. Materials are grouped for convenience
  2. Materials are grouped to study their properties
  3. Materials are grouped to remember their names
  4. Materials are grouped according to their uses

Answer: 3. Materials are grouped to remember their names

Question 26. Which of the following objects is not made up of metal?

  1. Wallet
  2. Knife
  3. Neavy machine
  4. Utensils

Answer: 1. Wallet

Question 27. Which one of the following objects will not tarnish in water?

  1. Iron piece
  2. Gold ring
  3. Silver ring
  4. Copper wire

Answer: 2. Gold ring

Question 28. A pair of objects having the same physical properties is

  1. Iron, bread
  2. Honey, sand
  3. Gold, silver
  4. Wood, cotton ball

Answer: 3. Gold, silver

Question 29. Pick one material from the following which is completely soluble in water.

  1. Chalk powder
  2. Tea leaves
  3. Glucose
  4. Sawdust

Answer: 3. Glucose

NCERT Class 6 Science Chapter 8 Light Shadows And Reflections Multiple Choice Questions

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Light Shadows And Reflections Multiple Choice Questions

Question 1. Observe the picture given in the figure carefully.

Class 6 Science Chapter 8 Light Shadows And Reflections Screen And Torch

A patch of light is obtained at B when the torch is lighted as shown. Which of the following is kept at position A to get this patch of light?

  1. A wooden board
  2. A glass sheet
  3. A mirror
  4. A sheet of white paper

Answer: 3. A mirror

Read and Learn More NCERT Class 6 Science MCQs

Question 2. Shadows may give us information regarding the

  1. Size of the object
  2. Surface
  3. Shape of the object
  4. Shape of the source

Answer: 3. Shape of the object

Question 3. The diagram shows a light source, an opaque object m and a screen

Class 6 Science Chapter 8 Light Shadows And Reflections Light Source And An Opaque And Screeen

What will be the shape of the shadow on the screen?

Class 6 Science Chapter 8 Light Shadows And Reflections Shape On The Screen

Answer: 3

Question 4. Which of the following is not always necessary to 1 observe a shadow?

  1. Sun
  2. Screen
  3. Source of light
  4. Opaque object

Answer: 1. Sun

Question 5. Paheli observed the shadow of a tree at 8:00 AM, 12:00 noon and 3:00 PM. Which of the following statements is the closest to her observation about the shape and size of the shadow?

  1. The shape of the shadow of the tree changes but the size remains the same.
  2. The size of the shadow of the tree changes but the shape remains the same.
  3. Both the size and shape of the shadow of the tree change.
  4. Neither the shape nor the size of the shadow changes.

Answer: 3. Both the size and shape of the shadow of the tree change.

NCERT Class 6 Science Chapter 8 Light Shadows And Reflections MCQs

Question 6. Which of the following can never form a circular shadow?

  1. A ball
  2. A flat disc
  3. A shoe box
  4. An ice cream cone

Answer: 3. A shoe box

Question 7. A student observes a tree given in the figure through a pinhole camera. Which of the diagrams given in figures (1) to (4) depicts the image seen by her

Class 6 Science Chapter 8 Light Shadows And Reflections Tree Given Through Pinhole Camera

Answer: 4

Question 8. Four students A, B, C and D looked through pipes of different shapes to see a candle flame 

Class 6 Science Chapter 8 Light Shadows And Reflections Candle Flames

Who will be able to see the candle flame?

  1. 1
  2. 2
  3. 3
  4. 4

Answer: 4. 4

Question 9. Two students while sitting across a table looked down True/False onto its top surface. They noticed that they could see their own and each other’s image. The table top is likely to be made of

  1. Unpolished wood
  2. Red stone
  3. Glass sheet
  4. Wood top covered with cloth

Answer: 3. Glass sheet

Question 10. The bouncing back of ray of light from the shining surface on which it was incident is known as

  1. Refraction
  2. Bending
  3. Reflection
  4. Dispersion

Answer: 3. Reflection

Question 11. Abha keeps a potted plant in front of a mirror

Class 6 Science Chapter 8 Light Shadows And Reflections Potted Plant Front Of A Mirror

From which point, can Abha see the image of the plant in the mirror?

  1. Point 1
  2. Point 2
  3. Point 3
  4. Point 4

Answer: 3. Point 3

Question 12. Which of the following is a luminous object?

  1. Chair
  2. Book
  3. Moon
  4. Torch

Answer: 4. Torch

Question 13. Which of the following cannot give off its light?

  1. Planet
  2. Electric bulb
  3. Torch
  4. Sun

Answer: 1. Planet

Question 14. Sachin can see through the glass because the glass is

  1. Transparent
  2. Translucent
  3. Opaque
  4. Reflective

Answer: 1. Transparent

Question 15. Which of the following is always necessary to observe a shadow?

  1. Screen
  2. Opaque object
  3. Source of light
  4. All of the above

Answer: 4. All of the above

Question 16. There are mainly three types of objects, based on their properties. Are you able to look through a transparent object? Yes, you can. Because it has a property to pass the light through it. Objects that allow light to pass through them completely are known as transparent objects. Pure water, plane glass, air, etc., are examples of such objects. Can you look through a brick wall? Probably you cannot. Because brick walls cannot allow light to pass through them. Those objects which do not allow light to pass through them are known as opaque objects. Wall and wood are examples of such objects. The third type of object is one which partially allows light to pass through them. Such types of objects are known as translucent objects. Examples are tracing paper, bathroom window glass, butter paper, etc.
Answer:

1. Which of the following is an opaque object?

  1. Glass
  2. Cardboard
  3. Air
  4. Pure water

Answer: 2. Cardboard

2. A transparent object allows light to

  1. Transmit completely
  2. Bounce back
  3. Partially pass
  4. None of these

Answer: 1. Transmit completely

3. A butter paper is an example of

  1. Translucent object
  2. Transparent object
  3. Luminous object
  4. All of these

Answer: 1. Translucent object

Question 17. Kabir has four sheets made of different materials. He tries to see a burning candle through each of the four sheets.

The table shows Kablr’s findings:

Class 6 Science Chapter 8 Light Shadows And Reflections Kabirs Finding And Sheets

Class 6 Science Chapter 8 Light Shadows And Reflections Kabirs Finding

1.  What can be concluded from Kabir’s activity?

  1. Sheet 2 is made of a transparent material.
  2. Sheet 4 is made of a translucent material.
  3. Sheet 2 and Sheet 3 are made of opaque materials.
  4. Sheet 1 and Sheet 4 are made of transparent materials.

Answer: 4. Sheet 1 and Sheet 4 are made of transparent materials.

2. Which of these should Kabir keep the same for the activity?

  1. Size of the sheets
  2. Size of the candle
  3. Thickness of the sheets

Answer: 3. Thickness of the sheets

3. A burning candle emits light. Which of these objects can also emit light?

  1. LED
  2. Gold
  3. Water
  4. Mirror

Answer: 1. LED

4. Which of these works on the principle of reflection of light?

  1. Television
  2. Traffic signal
  3. Periscope
  4. Electric torch

Answer: 2. Traffic signal