Our Environment | Term 3 Chapter 1 | 3rd Science - Questions with Answers

Our Environment | Term 3 Chapter 1 | 3rd Science

EVALUATION

I. Choose the correct answer.

1. Which of these is an example for biotic factor?

a. Water
b. Goat
c. Air

Answer : b. Goat

2. Our environment is surrounded by _______

a. biotic factors
b. abiotic factors
c. both biotic and abiotic factors

Answer : c. both biotic and abiotic factors

3. Human beings depend on _______ for their food.

a. plants
b. soil
c. wood

Answer : a.plants

4. ________are the primary producers.

a. Non green plants
b. Green plants
c. Dry leaves

Answer : b. Green plants

5. Which is an example for decomposer?

a. Mango tree
b. Bacteria
c. Deer

Answer : b. Bacteria

6. Which of these living things would die if there were no green plants on earth?

(a) a and c only
(b) b and d only
(c) d and a only
(d) a, b, c and d

Answer : (d) a, b, c and d

II. Fill in the blanks.

1. Cow is a consumer. (Cow / Soil )

2. A young plant is known as sapling. ( tree / sapling )

3. Planting of sapling provides oxygen (oxygen / land )

4. World Environment Day is June 5th ( June 15th / June 5th )

5. Decomposers get food from dead plants and animals. ( Decomposers / Producers ).

III. Match the following.

Try to match the items on the left with the correct category on the right before looking at the answers below.

Questions:

1. Stone - Consumer
2. Bacteria - Abiotic factor
3. Plants - Decomposer
4. Buffalo - Producers

Answer:

1. Stone - Abiotic factor
2. Bacteria - Decomposer
3. Plants - Producers
4. Buffalo - Consumer

IV. Say true or false.

1. Abiotic factors are important for biotic factors. (True)

2. River is an example for biotic factor. (False)

3. ‘Van Mahotsav’ is organised during the first week of July every year. (True)

4. Plants are the consumers. (False)

5. Plants provide food and shelter to living things. (True)

V. Answer the following.

1. Vijay placed two things ‘P’ and ‘R’ (one living and one non-living) in separate cages with food and water.

a. Which thing is likely to be a living thing? Give reason for your answer.

P thing is likely to be living thing. Because the weight increases from week 1 to week 4

b. What will be the weight of living thing in week 6?

12 kg

2. Write two examples for biotic and abiotic factors.

Biotic - Plants, Human beings
Abiotic - Water, Sun

3. Write any three differences between living and non-living things.

Living things
They can breathe and grow
They need food to live
They can feel

Non -living things
They cannot breathe and
They do not need food to live
They cannot feel

4. List the abiotic factors needed for insects.

Air, Soil

5. What are the biotic factors of a balanced ecosystem?

The biotic factors of a balanced ecosystem are producers, consumers and decomposers.

6. Why plants are called primary producers?

Green plants make their own food by the process of photosynthesis. Hence, they are called primary producers.

7. Write any four benefits of plants.

i) Provide oxygen for breathing
ii) Provide food and shelter to living things
iii) Help in bringing rainfall
iv) Offer a good environment to live.

VI. Project

Make an album by collecting pictures of different kinds of biotic and abiotic factors.

Let Us Try

1. Write the names of the animals that you see in the previous page picture.

Cow, Buffalo, Goat
Rabit, Monkey, Turtle

2. Classify the following into natural things and man-made things.

(Dam, river, coconut tree, building, jasmine flower, hill, cloud, silver vessel, cell phone, temple, cake, air, sun, ship, water, pencil, book, doll, football, sunflower, crocodile, aeroplane)

Natural things: River, hill, cloud, air, sun, water, coconut tree, jasmine flower, sun flower, crocodile

Man-made things: Dam, building, silver vessel, cell phone, temple, cake, ship, pencil, book, doll, foot ball, aeroplane

Let Us Enjoy

Shall we mimic like the animals?

Crow, Cuckoo, Elephant, Parrot, Donkey, Cow, Goat, Dog

Let Us Connect

Match the following sources with their products and uses.

Let Us Try

1. Classify the following as Biotic / Abiotic factors.

2. Think and Answer

a. A swing goes to and fro. Is it living or non-living?

Answer: non-living

b. We get wood from trees which are the living things. A chair is made from wood. Is the chair a living thing or a non-living thing?

Answer: non-living thing

Try to Answer

Look at the picture and answer the question. Which of the non-living things can float?

a. Iron rod
b. Stone
c. Air filled ball
d. Coin

Answer: c. Air filled ball

Let Us Try

The following statements describe some of the characteristics of living things. Identify and write the characteristic features using the given hints.

(Characteristics Hints: Move, Breathe, Feel, Needs Food, Grow, Reproduce)

Let Us Play

Divide the class into two groups and ask the first group to write any five biotic factors and the second group to write any five abiotic factors seen around the school.

Write the needs of the following.

1. Birds :

Air, Water, Sunlight, Insects, Trees

2. Insects :

Soil, Air, Plants, Small creatures

3. Human beings:

Air, Water, Plants, Sunlight, Animals.

Let Us Discuss

1. There is a large banyan tree in a park. Monkeys and birds have made the tree their home. Humans too spend time under the tree. Discuss with your friends, how the tree, monkeys, birds and humans are interdependent.

Birds and monkeys feed on the fruit. Birds build their nests in the tree. The tree gives shade to human beings when the day is hot. The wood of the tree is useful to human beings. The droppings of the birds are a manure to the tree. Birds play a vital role in dispersal of seeds. Thus the tree, monkeys, birds and human beings are interdependent.

2. Why is plant the most important living thing?

Because they make food from abiotic factors.

3. Discuss in a group and create an interlink of living and non-living factors.

Biotic and abiotic factors are linked to each other by the flow of energy through food.

Let Us Try

1. Write the abiotic factors needed for the following biotic factors to survive.

(Air, Water, Sunlight, Soil, Land, Wheat, Fruits, Grass, Hen)

a. Animals: Air, Water, Sunlight, Land, Grass

b. Plants: Air, Water, Sunlight, Soil

c. Human beings: Air, Water, Sunlight, Land, Wheat, Fruits, Hen

2. An animal that

a. flies in the air is: aerial

b. lives in water is: aquatic animals

c. moves on the ground is: Terrestrial animals

d. eats only plants is: Herbivores

Let Us Try

Classify the following biotic factors.

(Tulsi, Fungi, Mango tree, Rabbit, Eagle, Cat, Dog, Cucumber plant, Human, Grass, Crocodile, Crow, Bacteria)

Producers : Tulsi, Mango tree, Cucumber plant, Grass

Consumers : Rabbit, Eagle, Cat, Dog, Human, Crocodile, Crow

Decomposers : Fungi. Bacteria

Let Us Discuss

1. Let us discuss and write.

Plants and human beings are living things. Why do human beings depend on plants?

Human beings obtain food from plants and oxygen for respiration. So they depend on plants.

2. Divide the students into three groups and give them some pictures of living things. Ask them to classify the pictures based on their food habits.

3. Take your students outside the classroom or to a park. Ask them to note down the producers and consumers they could identify there.

Let Us Try

The names of several natural resources are hidden in the box below. Find as many as possible. Some words are repeated.

Let us Connect

Link the animals as herbivores, carnivores and omnivores.

Let Us Do

A. Write any two uses of trees.

1. Help in bringing rainfall
2. Provide oxygen

B. Conduct an awareness campaign on ‘Save Our Environment’.

C. Plant saplings in your school campus.

D. Preparation of seed ball

Take some clay, humus, add water and mix well. After mixing, place the available seeds inside them and make a seed ball. Then dry and keep it safe. Distribute the seed balls to public on special occasions of your school.

E. Write some slogans on ‘Save Plants’ and paste them on the tree in your school campus/road sides. (E.g., Take care of the Earth and it will take care of you. It’s not yours, nor mine, it’s ours)

1. Trees look fair, they clean the air.
2. Forests are our wealth. They preserve our health.

The nature of our future depends on the future of our nature.

Force | Term 1 Unit 3 | Class 3 Science | Complete Lesson & Activities

Unit 3 FORCE

Learning Objectives

After learning this lesson, students will be able to

* define movements and actions

* define force

* know different types of forces

* know the force of friction

* understand the need and significance of frictional force

1. Simple movements and actions

In our daily life, we do different actions such as pushing, pulling, twisting and turning. By doing these actions we move or change the shape of an object.

* Change in position of an object is called movement.

* Action is the motion which gives the required result.

Let us look at the pictures below to understand movement and action better

The player hits the ball with hockey stick,

Boys are riding bicycle.

In the above pictures,

What moves? The ball, The cycle.

What is the action? Hitting the ball , Riding the bicycle.

Motion

When an object or a thing moves from one place to another, it is said to be in motion.

Let us speak

2. Force

Force is a push or a pull on an object which make it move, changes its shape or stops it from moving.

* Force involves an interaction between two or more objects.

* Force can lift or drop an object.

Without force, we can‛t move any object.

Observe and Discuss

1. Push

Look and say: What kind of actions do the pictures denote?

Here, all the pictures show pushing action.

When a force is applied in the direction of an object, it is called push.

2. Pull

Look and say: What kind of actions do the pictures say?

Here all the actions show pulling action.

When a force is applied in the direction opposite to the direction of an object, it is called pull.

Put a tick (✓) mark for the pictures of motion.

Classify the following - Push or Pull?

Activities - Push/Pull

(i)

Riding the bicycle Push

(ii)

Moving the table towards you Pull

(iii)

Dragging the chair Pull

(iv)

Moving a car to start Push

(v)

Opening the window Push

(vi)

Stretching the rubber band Pull

(vii)

Removing the shoe laces Pull

3. Effect of forces

Energy is needed to apply force

Force helps us to do the following things:

*

Force can change the direction

*

Force can change the speed

*

Force can stop a moving object

*

Force can change the shape

Force changes direction

Here, in the picture, a boy hits the shuttlecock and it reaches the other boy. He hits it again with the racket to move it to the opposite direction.

Force changes motion

* The cycle moves forward because force is applied on the cycle by pedaling.

* When we stop pedaling the force is removed and the cycle stops and comes to rest.

Some applications of force in everyday life

Force can change the speed

Force can change the speed of a body which is already in motion by providing more force on it. Ram and his brother are playing with a toy car. Ram tries to move the toy car and his brother stops it from the opposite direction to slow down the toy car.

Thus, force changes the speed of an object.

Force can stop a moving object

An object stops moving when we apply force in the opposite direction.

* Have you played football game?

* How will you stop the ball?

* The goal keeper applies force and stops the ball.

Force can change the shape

* When an inflated balloon or water balloon is pressed, some force is applied on both sides of the balloon. Thus, it changes its shape.

* While squeezing a plastic water bottle force is applied on all sides of the bottle. Thus, the shape and size of the bottle is changed.

Do you know

Less force is required in pulling than in pushing. So it is easy to pull than push an object.

Match the following.

4. Types of force

A . Contact Force

When a force is applied by touching the object, it is called contact force.

Eg : Lighting a match stick

Contact force is classified into three.

1. Muscular force 2. Mechanical force 3. Frictional force

B . Non-Contact Force

When a force is applied without touching an object, it is called non-contact force.

Eg. Vaccum cleaner, Magnet.

Non - contact force is classified into two.

1. Gravitational force 2. Magnetic force

Muscular force

The force applied by using the parts of our body is called muscular force.

I use my legs to pedal. The force used here is muscular force.

I use my hands to make pots. The force used here is muscular force.

Mechanical force

The force applied by a machine is called mechanical force.

Gravitational force

* When you throw a ball up in the air, why does it come down?

* When we jump, why do we come down? Why don’t we fly?

Why do fruits fall down from the tree?

Why this happens?

The Earth pulls all the objects towards itself. The force applied by the Earth to pull objects towards itself is called gravitational force.

Magnetic force

A magnet is a material that attracts things made of iron. The force that attracts things is called magnetic force.

Observe the picture and write the kind of force involved here.

Tick (✓) the muscular force.

Frictional force

When we roll down a ball on grass ground, it slows down and finally stops. We know that an object cannot stop without force. The force that stopped the ball is frictional force. Force exerted by the surface when an object moves over it is called Frictional force.

Think!

Why do we sprinkle powder on the carom board before playing carrom?

To reduce the friction between the surface of the carrom board, the striker and the coins.

5. Friction

When we use eraser on a paper, the shape of the eraser changes. Why? It is because of the friction between the eraser and the paper.

Friction is a force actions between two surfaces in contact or when they slide over one another.

Do you Know?

Early man accidentally discovered fire by rubbing two flint stones (chikimuki kal) together. The frictional force between two stones created a spark.

List out the push activities

(i)

Swing,

(ii)

Playing foot ball,

(iii)

Kids scooter, cycling.

List out the pull activity

(i)

Pulling wood,

(ii)

Pulling trolley,

(iii)

Kiting.

List the frictions here

(i)

Sliding,

(ii)

Playing in sand,

(iii)

See saws.

Rainwater Harvesting: Methods and Advantages | Environmental Management

10th Science : Chapter 22 : Environmental Management

Rainwater Harvesting

What is Rainwater Harvesting?

Rainwater Harvesting

Rainwater harvesting is a technique of collecting and storing rainwater for future use. It is a traditional method of storing rain water in underground tanks, ponds, lakes, check dams and used in future.

The main purpose of rainwater harvesting is to make the rainwater percolate under the ground so as to recharge ‘groundwater level’.

Methods of rainwater harvesting

(i) Roof top rainwater harvesting:

Roof-tops are excellent rain catchers. The rain water that falls on the roof of the houses, apartments, commercial buildings etc. is collected and stored in the surface tank and can be used for domestic purpose.

(ii) Recharge pit:

In this method, the rainwater is first collected from the roof tops or open spaces and is directed into the percolation pits through pipes for filtration. After filtration the rainwater enters the recharge pits or ground wells.

People living in rural areas adopt a variety of water collecting methods to capture and store as rain water. Some of the methods used are

(i) Digging of tanks or lakes (Eris):

It is one of the traditional water harvesting system in Tamil Nadu. Eris are constructed in such a way that if the water in one eri overflows, it automatically gets diverted to the eri of the next village, as these eris are interconnected.

(ii) Ooranis:

These are small ponds to collect rainwater. The water is used for various domestic purposes (drinking, washing and bathing). These ponds cater the nearby villages.

Advantages of rainwater harvesting

Rainwater harvesting helps to

• Overcome the rapid depletion of ground water levels.
• To Meet the increase demand of water.
• Reduces flood and soil erosion
• Water stored in ground is not contaminated by human and animal wastes and hence can be used for drinking purpose.

Electrical Energy Management: Conservation Methods | 10th Science

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail for 10th Science : Chapter 22 : Environmental Management : Electrical Energy Management

Electrical Energy Management

Electrical Energy Management

Electricity or electric power is produced by generators. The generators are operated by the turbines attached to it. The turbines are rotated by steam, moving water or wind power to produce electricity.

Conservation of electrical energy

The following measures can be taken even at home and school to save electricity

• Use energy efficient appliances to save electricity like Compact Fluorescent Lamps (CFL), Light Emiting Diode (LED) bulbs and other electric equipments.
• Switch off the lights and fans, television and other electrical appliances when not in use.
• Switch of the mobile phone chargers when not in use.
• Maximise the use of solar radiation. Solar water heating system can be used instead of electric geysers.
• Minimise the use of air conditioners.

Sewage Management: Sources and Treatment Methods | 10th Science Environmental Management

Chapter: 10th Science : Chapter 22 : Environmental Management

Sewage Management

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

Untreated sewage or wastewater generated from domestic and industrial process is the leading polluter of water sources in India. Sewage water results in agricultural contamination and environmental degradation.

Sewage Management

Untreated sewage or wastewater generated from domestic and industrial process is the leading polluter of water sources in India. Sewage water results in agricultural contamination and environmental degradation.

Sources of Sewage/wastewater

• Domestic purpose or household activities
• Dye and textile industries
• Leather industries
• Sugar and breweries industries
• Paper and pulp industries

Figure 22.4 A view of a sewage treatment plant.

Sewage/wastewater treatment method

The conventional wastewater treatment methods involve the following steps (a) Pre-screening (b) Aeration (c) Sludge Management and (d) Water Reuse.

Pre-screening: Wastewater generated from domestic and industrial activities is screened to remove soil and solid particulates.

Aeration: Screened wastewater is then pumped to an aeration tank. Here the microbial contaminants are removed by the biological degradation that occurs in the presence of air.

Sedimentation process: In this process, the solid particles in suspension form are allowed to settle. The particles that settle out from the suspension is known as sludge.

Sludge removal: The sludge generated by the degradation process is transferred periodically from the tank for safe disposal.

Disinfection: Chlorination and ultraviolet (UV) radiation of treated water is required to remove any microorganism contamination.

Water recycling: The water will then be supplied for domestic or industrial purposes.

Periodic Classification of Elements: Class 10 Science Book Back Answers

Book Back Questions with Answers - Periodic Classification of Elements

I. Choose the best answer.

1. The number of periods and groups in the periodic table are______.

• a) 6,16
• b) 7,17
• c) 8,18
• d) 7,18

2. The basis of modern periodic law is______.

• a) atomic number
• b) atomic mass
• c) isotopic mass
• d) number of neutrons

3. _____ group contains the member of halogen family.

• a) 17^th
• b) 15^th
• c) 18^th
• d) 16^th

4. _____ is a relative periodic property

• a) atomic radii
• b) ionic radii
• c) electron affinity
• d) electronegativity

5. Chemical formula of rust is ________.

• a) FeO.xH₂O
• b) FeO₄.xH₂O
• c) Fe₂O₃.xH₂O
• d) FeO

6. In the alumino thermic process the role of Al is _____.

• a) oxidizing agent
• b) reducing agent
• c) hydrogenating agent
• d) sulphurising agent

7. The process of coating the surface of metal with a thin layer of zinc is called______.

• a) painting
• b) thinning
• c) galvanization
• d) electroplating

8. Which of the following have inert gases 2 electrons in the outermost shell.

• a) He
• b) Ne
• c) Ar
• d) Kr

9. Neon shows zero electron affinity due to _____.

• a) stable arrangement of neutrons
• b) stable configuration of electrons
• c) reduced size
• d) increased density

10. ______ is an important metal to form amalgam.

• a) Ag
• b) Hg
• c) Mg
• d) Al

II. Fill in the blanks

1. If the electronegativity difference between two bonded atoms in a molecule is greater than 1.7, the nature of bonding is ionic.

2. 6^th is the longest period in the periodical table.

3. Atomic number forms the basis of modern periodic table.

4. If the distance between two Cl atoms in Cl₂ molecule is 1.98Å, then the radius of Cl atom is 0.99 Å.

5. Among the given species A^–, A⁺, and A, the smallest one in size is A⁺.

6. The scientist who propounded the modern periodic law is Henry Moseley.

7. Across the period, ionic radii decreases (increases,decreases).

8. Lanthanides and Actinides are called inner transition elements.

9. The chief ore of Aluminium is Bauxite.

10. The chemical name of rust is hydrated ferric oxide.

III. Match the following

Question:

• 1. Galvanisation : Noble gas elements
• 2. Calcination : Coating with Zn
• 3. Redox reaction : Silver-tin amalgam
• 4. Dental filling : Alumino thermic process
• 5. Group 18 elements : Heating in the absence of air

Answer:

• 1. Galvanisation Coating with Zn
• 2. Calcination Heating in the absence of air
• 3. Redox reaction Alumino thermic process
• 4. Dental filling Silver-tin amalgam
• 5. Group 18 elements Noble gas elements

IV. True or False: (If false give the correct statement)

1. Moseley’s periodic table is based on atomic mass.

False.

Correct Statement: Moseley's periodic table is based on atomic number.

2. Ionic radius increases across the period from left to right.

False.

Correct Statement: Ionic radius decreases across the period from left to right.

3. All ores are minerals; but all minerals cannot be called as ores.

True.

4. Al wires are used as electric cables due to their silvery white colour.

False.

Correct Statement: Al wires are used in electric cables as they are good conductors of electricity.

5. An alloy is a heterogenous mixture of metals.

False.

Correct Statement: An alloy is a homogeneous mixture of metals.

V. Assertion and Reason

Answer the following questions using the data given below:

• i. A and R are correct, R explains the A.
• ii. A is correct, R is wrong.
• iii. A is wrong, R is correct.
• iv. A and R are correct, R doesn’t explains A.

1.

Assertion: The nature of bond in HF molecule is ionic.

Reason: The electronegativity difference between H and F is 1.9.

i. A and R are correct, R explains the A.

2.

Assertion: Magnesium is used to protect steel from rusting.

Reason: Magnesium is more reactive than iron.

iii. A is wrong, R is correct.

3.

Assertion: An uncleaned copper vessel is covered with greenish layer.

Reason: copper is not attacked by alkali.

i. A and R are correct, R explains the A.

VI. Short answer questions

1. A is a reddish brown metal, which combines with O₂ at < 1370 K gives B, a black coloured compound. At a temperature > 1370 K, A gives C which is red in colour. Find A, B and C with reaction.

Reddish brown metal A is copper.

2. A is a silvery white metal. A combines with O₂ to form B at 800°C, the alloy of A is used in making the aircraft. Find A and B.

Silvery white metal is aluminium.

3. What is rust? Give the equation for formation of rust.

When iron is exposed to moist air, it forms a layer of brown hydrated ferric oxide on its surface. This compound is known as rust and the phenomenon of formation of rust is known as rusting.

4Fe + 3O2 + xH2O → 2Fe2O3.xH2O (rust)

4. State two conditions necessary for rusting of iron.

Two conditions necessary for rusting iron are (i) Oxygen and (ii) Water.

VII. Long answer questions

1. a) State the reason for addition of caustic alkali to bauxite ore during purification of bauxite.

b) Along with cryolite and alumina, another substance is added to the electrolyte mixture. Name the substance and give one reason for the addition.

a) Caustic soda solution at 150°C is added to bauxite ore to obtain Sodium Meta Aluminate.

b) Fluorspar is added to the electrolyte mixture so as to lower the fusion temperature of the electrolyte.

2. The electronic configuration of metal A is 2,8,18,1. The metal A when exposed to air and moisture forms B a green layered compound. A with con. H₂SO₄ forms C and D along with water. D is a gaseous compound. Find A, B, C and D.

Metal A is copper.

2Cu + O2 + CO2 + H2O → CuCO3.Cu(OH)2

2Cu [A:Copper] + O2 + CO2 + H2O → CuCO3.Cu(OH)2 [B:Basic copper carbonate]

Cu + 2H2SO4 → CuSO4 + SO2 ↑ + H2O

Cu [A:Copper] + 2H2SO4 → CuSO4 [C:Copper sulphate] + SO2 ↑ [D:Sulphur-di-oxide] + H2O

[A: Cu : Copper]

[B: CuCO₃.Cu(OH)₂ : Basic copper carbonate]

[C: CuSO₄ : Copper sulphate]

[D: SO₂ : Sulphur-di-oxide]

3. Explain smelting process.

Smelting: Smelting is the process of reducing the roasted metallic oxide from the metal in its molten condition. In this process, impurities are removed as slag by the addition of flux.

VIII. HOT questions

1. Metal A belongs to period 3 and group 13. A in red hot condition reacts with steam to form B. A with strong alkali forms C. Find A, B and C with reactions.

Metal A is Aluminium.

2Al + 3H2O → Al2O3 + 3H2

2Al [(A) Aluminium] + 3H2O → Al2O3 [(B) Aluminium oxide] + 3H2

2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2 ↑

2Al + 2NaOH + 2H2O → 2NaAlO2 [C: Sodium meta aluminate] + 3H2 ↑

(A) : Al : Aluminium

(B) : Al₂O₃ : Aluminium oxide

(C) : 2NaAlO₂ : Sodium meta aluminate

2. Name the acid that renders aluminium passive. Why?

Dilute or concentrated nitric acid does not attack aluminium, but it renders aluminium passive due to the formation of an oxide film on its surface.

3. a) Identify the bond between H and F in HF molecule.

b) What property forms the basis of identification?

c) How does the property vary in periods and in groups?

a) Ionic bond

b) Electronegativity

c) Along the period, from left to right in the periodic table, the electronegativity increases. On moving down a group, the electronegativity of the elements decreases.

Concept Map

Occurrence of Ores in Tamil Nadu | 10th Science Chapter 8

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

10th Science : Chapter 8 : Periodic Classification of Elements : Occurrence of Ores in Tamil Nadu |

Occurrence of Ores in Tamil Nadu

Chapter: 10th Science : Chapter 8 : Periodic Classification of Elements

(Reference: mineral resources of Tamil Nadu-ENVIS Centre, Tamil Nadu)

OCCURRENCE OF ORES IN TAMIL NADU

• Lime stone: Coimbatore, Cuddalore, Dindugul
• Gypsum: Tiruchi and Coimbatore Distiricts
• Titanium minerals: Kanyakumari, Tirunelveli and Tuticorin.
• Chromite: Coimbatore and Salem district.
• Magnetite: Dharmapuri, Erode, Salem, Thiruvannamalai.
• Tungsten: Madurai and Dindugal.

(Reference: mineral resources of Tamil Nadu-ENVIS Centre, Tamil Nadu)

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

10th Science : Chapter 8 : Periodic Classification of Elements : Occurrence of Ores in Tamil Nadu |

Understanding the Modern Periodic Table: Periods, Groups, and Properties

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail for 10th Science : Chapter 8 : Periodic Classification of Elements.

Modern Periodic Table

MODERN PERIODIC TABLE

With reference to the modern periodic law, the elements were arranged in the increasing order of their atomic numbers to form the modern periodic table. The modern periodic table is a tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of the elements. Figure 8.1 shows the modern periodic table of 118 elements discovered so far.

As you have studied the features of the modern periodic table in standard IX, here let us confine to the study of the features of periods and groups.

1. Features of Periods

The horizontal rows are called periods. There are seven periods in the periodic table.

• First period (Atomic number 1 and 2): This is the shortest period. It contains only two elements (Hydrogen and Helium).
• Second period (Atomic number 3 to 10): This is a short period. It contains eight elements (Lithium to Neon).
• Third period (Atomic number 11 to 18): This is also a short period. It contains eight elements (Sodium to Argon).
• Fourth period (Atomic number 19 to 36): This is a long period. It contains eighteen elements (Potassium to Krypton). This includes 8 normal elements and 10 transition elements.
• Fifth period (Atomic number 37 to 54): This is also a long period. It contains 18 elements (Rubidium to Xenon). This includes 8 normal elements and 10 transition elements.
• Sixth period (Atomic number 55 to 86): This is the longest period. It contains 32 elements (Caesium to Radon). This includes 8 normal elements, 10 transition elements and 14 inner transition elements (Lanthanides).
• Seventh period (Atomic number 87 to 118): Like the sixth period, this period also accommodates 32 elements. Recently 4 elements have been included by IUPAC.

2. Features of Groups

The vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the periodic table.

Based on the common characteristics of elements in each group, they can be grouped as various families.

The Lanthanides and Actinides, which form part of Group 3 are called inner transition elements.

Except 'group 0', all the elements present in each group have the same number of electrons in their valence shell and thus have the same valency. For example, all the elements of group 1 have one electron in their valence shells (1s1). So, the valency of all the alkali metals is ‘1’.

As the elements present in a group have identical valence shell electronic configurations, they possess similar chemical properties.

The physical properties of the elements in a group such as melting point, boiling point and density vary gradually.

The atoms of the 'group 0' elements have stable electronic configuration in their valence shells and hence they are unreactive.

Modern Periodic Law: Periodic Classification of Elements | Class 10 Science Chapter 8

Study Material | Class 10 Science | Chapter 8: Periodic Classification of Elements

Modern Periodic Law

MODERN PERIODIC LAW

Mendeleev’s periodic table had some discrepancies, which were difficult to overcome. For example, the atomic mass of argon (39.95 amu) is greater than that of potassium (39.10 amu), but argon comes before potassium in the periodic table. If elements were arranged solely according to increasing atomic mass, argon would appear in the position occupied by potassium in our modern periodic table. No chemist would place argon, a gas with no tendency to react, in the same group as lithium and sodium,which are two highly reactive metals. This kind of discrepancies suggested that some fundamental property other than atomic mass must be the basis of periodicity. The fundamental property turned out to be the number of protons in an atom’s nucleus, something that could not have been known by Mendeleev and his contemporaries.

Henry Moseley, a British scientist in 1912, discovered a new property of elements called atomic number, which provided a better basis for the periodic arrangement of the elements. It is a well-known fact that atomic number of an element is equal to the number of protons or the number of electrons present in the neutral atom of an element. The periodic law was, therefore, modified to frame a modern periodic law, which states that

“The physical and chemical properties of the elements are the periodic functions of their atomic numbers”.

Key Points to Remember: Atoms and Molecules | Class 10 Science Chapter 7

Atoms and Molecules: Points to Remember

Isotopes

Two or more forms of an element having the same atomic number, but different mass number are called Isotopes.

Example: (³⁵₁₇Cl, ³⁷₁₇Cl)

Isobars

Atoms of different elements having the same mass number, but different atomic numbers are called Isobars.

Example: (⁴⁰₁₈Ar, ⁴⁰₂₀Ca)

Isotones

Atoms of different elements having the same number of neutrons, but different atomic number and different mass number are called Isotones.

Example: (¹³₆C, ¹⁴₇N)

Relative Atomic Mass

Relative atomic mass of an element is the ratio between the mass of one atom of the element to 1/12th of the mass of the atom of carbon -12.

Average Atomic Mass

Average atomic mass of an element is calculated by adding the masses of its isotopes, each multiplied by their natural abundance on the Earth.

Relative Molecular Mass

Relative molecular mass of a molecule is the ratio between the mass of one molecule of the substance to 1/12th of the mass of the atom of carbon – 12.

Avogadro’s Law

The Avogadro’s law states that “equal volumes of all gases under similar conditions of temperature and pressure contain equal number of molecules”.

Vapour Density

The vapour density is defined as “the ratio between the masses of equal volumes of a gas (or a vapour) and hydrogen under the same condition”.

Atomicity

Atomicity of a monoatomic element can be calculated using the formula:

Atomicity = Molecular mass / Atomic Mass

Molecular Mass & Vapour Density

The relationship between molecular mass and vapour density is:

Molecular mass = 2 × Vapour density

Applications of Avogadro’s Law | 10th Science | Chapter 7: Atoms and Molecules

Applications of Avogadro’s Law

Chapter 7: Atoms and Molecules | Class 10 Science

Overview

It explains Gay-Lussac’s law. It helps in the determination of atomicity of gases.

APPLICATIONS OF AVOGADRO’S LAW

• It explains Gay-Lussac’s law.
• It helps in the determination of atomicity of gases.
• Molecular formula of gases can be derived using Avogadro’s law
• It determines the relation between molecular mass and vapour density.
• It helps to determine gram molar volume of all gases (i.e, 22.4 litre at S.T.P)

Mole Concept Explained: Class 10 Science Notes on Atoms and Molecules

Mole Concept

Introduction to the Mole Concept

So far we discussed about matters in terms of individual atoms and molecules. Atomic mass units provide a relative scale for the masses­ of the elements. Since the atoms have such small masses, no usable scale can be devised to weigh them in the calibrated units of atomic mass units. In any real situation, we deal with ­macroscopic samples containing enormous number of atoms­. Therefore, it is convenient to have a special unit to describe a very large number of atoms. The idea of a ‘unit’ to denote a ­particular number of objects is not new. For example, the pair (2 items) and the dozen (12 items), are all familiar units. Chemists measure atoms and molecules in ‘moles’. So, you can now understand that ‘mole’ denotes a number of particles.

In the SI system, the mole (mol) is the amount of a substance that contains as many elementary entities (atoms, molecules, or other particles) as there are atoms in exactly 12 g (or 0.012 kg) of the carbon-12 isotope. The actual number of atoms in 12 g of carbon-12 is determined experimentally. This is called Avogadro’s Number (N_A), named after an Italian scientist Amedeo Avogadro who proposed its significance. Its value is 6.023 × 10²³. So one mole of a substance contains 6.023 × 10²³ entities. Thus, 5 moles of oxygen molecules contain 5 × 6.023 ×10²³ molecules.

Mole Concept: The study of the collection of particles by using mole as the counting unit, in order to express the mass and volume of such unit particles in a bulk of matter is known as mole concept.

Calculating the Number of Moles

The number of moles of a substance can be calculated by various means depending on the data available, as follows:

• Number of moles of molecules.
• Number of moles of atoms.
• Number of moles of a gas (Standard molar volume at STP = 22.4 litre).
• Number of moles of ions.

Figure 7.3: Mole Concept Relationships

Note: STP-Standard Temperature and Pressure (273.15 K, 1.00 atm)

Mole of atoms:

One mole of an element contains 6.023 × 10²³ atoms and it is equal to its gram atomic mass.

i.e., one mole of oxygen contains 6.023 × 10²³ atoms of oxygen and its gram atomic mass is 16 g.

Mole of molecules:

One mole of matter contains 6.023 × 10²³ molecules and it is equal to its gram molecular mass.

i.e., one mole of oxygen contains 6.023 × 10²³ molecules of oxygen and its gram molecular mass is 32 g.

Molar volume:

One mole of any gas occupies 22.4 litre or 22400 ml at S.T.P. This volume is called as molar volume.

Calculation of number of moles by Different modes

Number of moles = Mass / Atomic Mass

Number of moles = Mass / Molecular mass

Number of moles = Number of Atoms / 6.023 × 10²³

Number of moles = Number of Molecules / 6.023 × 10²³

Figure 7.3: Mole Concept Summary

Difference Between Atoms and Molecules | Chapter 7 | 10th Science Study Notes

Difference Between Atoms and Molecules

DIFFERENCE BETWEEN ATOMS AND MOLECULES

Even though atoms are the basic components­ of molecules, they differ in many aspects when compared to the molecules. Table 7.5 consolidates the major difference between ­atoms and molecules.

Difference between atoms and molecules

Atom

1. An atom is the smallest particle of an element.
2. Atom does not exist in free state except in a noble gas.
3. Except some of noble gas, other atoms are highly reactive.
4. Atom does not have a chemical bond.

Molecule

1. A molecule is the smallest particle of an element or compound.
2. Molecule exists in a free state.
3. Molecules are less reactive.
4. Atoms in a molecule are held by chemical bonds.

Molecule and Molecular Mass: A Detailed Guide for Class 10 Science

Molecule and Molecular Mass

MOLECULE AND MOLECULAR MASS

Except noble gases, atoms of most of the elements are found in the combined form with itself or atoms of other elements. It is called as a molecule. A molecule is a combination of two or more atoms held together by strong chemical forces of attraction, i.e. chemical bonds.

1. Classification of molecules

A molecule may contain atoms of the same element or may contain atoms of two or more elements joined in a fixed ratio, in accordance with the law of definite proportions. Thus, a molecule may be an element or a compound. If the molecule is made of similar kind of atoms, then it is called homoatomic molecule.

The molecule that consist of atoms of different elements is called heteroatomic molecule. A compound is a heteroatomic molecule. The number of atoms present in the molecule is called its ‘atomicity’.

Let us consider oxygen. Oxygen gas exists in two allotropic forms: Oxygen (O₂) and Ozone (O₃). In oxygen molecule, there are two oxygen atoms. So its atomicity is two. Since both the atoms are similar, oxygen (O₂) is a homodiatomic molecule. Other elements that exist as diatomic molecules are hydrogen (H₂), nitrogen (N₂) and halogens: fluorine (F₂), chlorine (Cl₂), bromine (Br₂) and iodine (I₂).

Ozone (O₃) contains three oxygen atoms and hence it is called homotriatomic molecule. If a molecule contains more than three atoms, then it is called polyatomic molecule.

Conisder hydrogen chloride. It consists of two atoms, but of different elements, i.e. hydrogen and chlorine. So, its atomicity is two. It is a heterodiatomic molecule. Similarly, the water molecule contains two hydrogen atoms and one oxygen atom. So its atomicity is three. It is a heterotriatomic molecule.

2. Relative Molecular Mass (RMM)

As the molecules are made of atoms, they also have their own mass. The mass of the molecule of an element or compound is measured in the C-12 scale and hence called relative molecular mass.

The Relative Molecular Mass of a molecule is the ratio between the mass of one molecule of the substance to 1/12th mass of an atom of Carbon -12.

The relative molecular mass is obtained by adding together the relative atomic masses of all the atoms present in a molecule.

Calculation of relative molecular mass – Solved examples:

Example 1: Sulphuric acid (H₂SO₄)

Relative molecular mass of sulphuric acid (H₂SO₄) is calculated as follows: Sulphuric acid conatins 2 atoms of hydrogen, 1 atom of sulphur and 4 atoms of oxygen.

Therefore, Relative molecular mass of sulphuric acid = (2 × mass of hydrogen) + (1 × mass of sulphur) + (4 × mass of oxygen)

= (2 × 1) + (1 × 32) + (4 × 16)

= 98

i.e., one molecule of H₂SO₄ is 98 times as heavy as 1/12th of the mass of a carbon –12.

Example 2: Water (H₂O)

Relative molecular mass of water (H₂O) is calculated as follows: A water molecule is made of 2 atoms of hydrogen and one atom of oxygen.

So, the relative molecular mass of water = (2 × mass of hydrogen) + (1 × mass of oxygen)

= (2 × 1) + (1 × 16)

= 18

i.e., one molecule of H₂O is 18 times as heavy as 1/12th of the mass of a carbon –12.