GARBAGE IN GARBAGE OUT

 NOTES

What is Garbage?

All the waste materials and other household waste produced on a daily basis are termed as garbage. The different wastes of garbage contain peels of vegetable and fruits, leftovers cooked food products, waste paper, and plastic materials, and many other waste items.

Waste

Waste is any substance, which is discarded after primary use, or it is worthless, defective and of no use.

Composting and Vermicomposting

Compost

• Compost is an organic matter that has been decomposed and recycled as a fertilizer and soil nutrient.

Vermicomposting

• Vermicompost (or vermicompost) is the product of the composting process using various species of worms.
• Red wigglers, White worms and other earthworms are used to create a mixture of decomposing vegetables or food waste, garden waste, farm waste etc
• The product, vermicompost, is excellent manure for gardens, nurseries, farms etc.

Exercise Questions

1. (a) Which kind of garbage is not converted into compost by the red worms?

(b) Have you seen any other organism besides red worms, in your pit? If yes, try to find out their names. Draw pictures of these.

Solution:

a) Pieces of cloth, polythene bags, broken glass, aluminium wrappers, nails and broken toys are not converted into compost by the red worms.

b) Earthworms, small insects like ant, millipedes are found in pits.

2. Discuss:

(a) Is garbage disposal the responsibility only of the government?

(b) Is it possible to reduce the problems relating to disposal of garbage?

Solution:

a) No, not just the government, but everybody is responsible for garbage disposal. We should bifurcate wet and dry waste, recycle the non-biodegradable substances and we should also reduce the accumulation of garbage in our house and streets.

b) Yes, it is possible to reduce the problems of garbage by scientific disposal of garbage, we can do it by bifurcation of different waste and also by recycling the waste materials.

3. (a) What do you do with the leftover food at home?

(b) If you and your friends are given the choice of eating in a plastic plate or a banana leaf platter at a party, which one would you prefer and why?

Solution:

(a) Leftover food can be collected and used to form compost. Compost produces nutrients necessary for the growth and development of plants.

(b) We would prefer to eat food on a banana leaf plate because it acts as a harmless substance which helps to form  manure by the process of composting, whereas plastic plates cannot be converted into harmless substances by composting. Plastic plates are not degradable, hence can persist in the environment and cause many problems.

4. (a) Collect pieces of different kinds of paper. Find out which of these can be recycled.

(b) With the help of a lens look at the pieces of paper, you collected for the above question. Do you see any difference in the material of recycled paper and a new sheet of paper?

Solution:

(a) Papers such as newspapers, notebooks, magazines can be recycled easily. However, shiny and coated papers cannot be easily recycled

(b)  Recycled paper is usually thick or rough when compared to a new sheet of paper.

5. (a)Collect different kinds of packaging material. What was the purpose for which each one was used? Discuss in groups.

(b) Give an example in which packaging could have been reduced?

(c) Write a story on how packaging increases the amount of garbage.

Solution:

(a) Different kinds of packaging materials used commonly are:

Cardboard – used as shoe, soap, bulb and other boxes.

Plastic Bags – Toys covers, sarees bags, shopping bags, etc.

Wooden Boxes – Fruit baskets and boxes for hardware.

Jute Bags – School bags, shopping bags, vegetable bags, etc.

(b) By reusing the packaging material, we can reduce the accumulation of garbage.

(c) The basic purpose of packaging is to protect the product from tampering and to maintain its freshness and purity. However, most of the packaging material is used to beautify the boxes and make them look attractive on the shelves. Unfortunately, a large volume of packaging material goes waste and is thrown into the dustbin.

For example, in most of the places, the dustbins are full of chips and biscuit wrappers.

It unnecessarily increases the amount of garbage. It also increases the cost of the product due to unnecessary packaging. We should seriously consider how to reduce unnecessary packaging.

6. Do you think it is better to use compost instead of chemical fertilizers? Why?

Solution:

Yes, it is better to use compost instead of chemical fertilizers for the following reasons:

• It is easy to prepare compost
• Compost is environment friendly as it does not cause any health issues in humans and animals
• Compost will not cause pollution
• Compost increases soil fertility.
• Compost is biodegradable.

Air around us...

Excercise questions.

1. What is the composition of air?

Solution:

Air comprises water vapour, Oxygen, Nitrogen, Carbon dioxide, dust and smoke.

2. Which gas in the atmosphere is essential for respiration?

Solution:

Oxygen in the atmosphere is essential for respiration.

3. How will you prove that air supports burning?

Solution:

Place two candles of the same length on a table. Light both the candles. Cover one of the candles with an inverted glass tumbler. We observe that the candle covered with a glass tumbler got extinguished after some time, whereas the other candle continued burning. The candle gets extinguished because the component inside of the glass tumbler, which supports burning, is limited. Most of the component is used up by the burning candle. However, the other candle is getting continued supply of air. This component of air, which supports burning, is known as oxygen.

4. How will you show that air is dissolved in water?

Solution:

Take some water in a container. Heat it slowly on a tripod stand. Before water begins to boil, look at the inner surface of the container. We observe tiny bubbles inside. 

These bubbles come from the air dissolved in water. When you heat the water, to begin with, the air dissolved in it escapes. This experiment concludes air is present in the water.

5. Why does a lump of cotton wool shrink in water?

Solution:

The lump of cotton wool shrink in water because the air inside the cotton lumps are replaced by water which makes the layer stick together.

6. The layer of air around the earth is known as ___________.

Solution:

The layer of air around the earth is known as the atmosphere.

7. The component of air used by green plants to make their food, is ___________.

Solution:

The component of air used by green plants to make their food is carbon dioxide.

8. List five activities that are possible due to the presence of air.

Solution:

Activities that are possible due to air are:

Photosynthesis

Cloud formation

Respiration

Transpiration

Winnowing

9. How do plants and animals help each other in the exchange of gases in the atmosphere?

Solution:

During the process of respiration, animals and plants consume oxygen from the air and release carbon dioxide gas in the air. But green plants also release oxygen gas by utilizing carbon dioxide during the process of photosynthesis. Hence, in this way, plants and animals help each other in the exchange of gases in the atmosphere.

WATER

 NOTES

Water cycle: It is circulation of water through the process of evaporation or condensation as rain or snowfall. Water cycle is like a ring. In nature, the water cycle takes place from sea to land and back to sea again.

Evaporation

• The process of changing water to its vapour form is known as evaporation.
• Evaporation takes place from open surfaces of water all the time—day and night.
• Evaporation of water takes place continuously from oceans, rivers, lakes, wells and soil. Oceans, seas, rivers, lakes, ponds and wells together are often known as water bodies.
• During the day time, sunlight falls on the water in oceans, rivers, lakes. The fields, roads, rooftops and other land areas also receive sunlight. The sunlight also carries heat with it. As a result, water from oceans, rivers, lakes and the soil, and other land areas gets continuously changed into vapour.
• Thus, water vapour gets continuously added to air due to evaporation.

Transpiration

• Transpiration: It is the loss of water from the leaves of plants in the form of vapour.
• Every plant, whether it is in a crop field, a forest, on the roadside or in a kitchen garden, transpires to give off water vapour. The amount of water vapour that goes into air through the process of transpiration is very huge.

Condensation

• Condensation: The process of conversion of vapour into liquid form of water is called condensation.
• The process of condensation is opposite to evaporation.
• Cloud formation: The climate close to the earth’s surface is warm. It gets cooled as one goes up in atmosphere. Water vapour being lighter, rises up in the atmosphere. At the upper layer of atmosphere, where the temperature is lower, the vapour gets condensed into tiny water droplets and forms clouds.

Precipitation

• Precipitation: Clouds carry small droplets of water in them. It may so happen that many droplets of water come together to form larger sized drops of water. Such drops of water may become so heavy that they begin to fall. Falling of water drops is called precipitation.
• Rain: If the water during precipitation remains liquid till it reaches the surface of the earth, we have rains.
• Hail/Snow: Sometimes precipitation may be in the form of hail or snow. Water in a hail or snow is in its frozen or solid form.
• Dew: Many times, especially during winter nights, the air near the surface becomes quite cool. As a result, the water vapour present in it condenses to form water droplets. These water droplets appear as dew.
• Water table: If you take soil from ground, it has air as well as water. As you go down, the amount of water increases and air decreases. A level below surface, where it is only water, is called the water table.

Rainwater harvesting: The process of collecting and storing rainwater from roofs or a surface catchment is called rainwater harvesting.

Exercise Questions

1. Fill up the blanks in the following:

(a) The process of changing of water into its vapour is called _________________.

(b) The process of changing water vapour into water is called _________________.

(c) No rainfall for a year or more may lead to _________________ in that region.

(d) Excessive rains may cause _________________.

Solution:

(a) The process of changing of water into its vapour is called evaporation.

(b) The process of changing water vapour into water is called condensation.

(c) No rainfall for a year or more may lead to drought in that region.

(d) Excessive rains may cause floods.

2. State for each of the following whether it is due to evaporation or condensation:

(a) Water drops appear on the outer surface of a glass containing cold water.

(b) Steam rising from wet clothes while they are ironed.

(c) Fog appearing on a cold winter morning.

(d) Blackboard dries up after wiping it.

(e) Steam rising from a hot girdle when water is sprinkled on it.

Solution:

(a) Condensation

(b) Evaporation

(c) Condensation

(d) Evaporation

(e) Evaporation

3. Which of the following statements are “true” ?

(a) Water vapour is present in air only during the monsoon. ( )

(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.( )

(c) The process of water changing into its vapour, is called evaporation.( )

(d) The evaporation of water takes place only in sunlight.( )

(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.( )

Solution:

a) False

b) False

c) True

d) False

e) True

4. Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help? If yes, how?

Solution:

Spreading uniform near an anghiti or heater will help because it increases the rate of evaporation due to heat.

5. Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a droplets of water around it. Why?

Solution:

This is because the surface of the air around the bottle cools down and air condenses around the bottle.

6. To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet.

Solution:

The air we breathe out contains water vapour which condenses on the surface of the spectacles. So, the glass becomes wet and with the help of a small amount of water molecules, it becomes easier to clean the spectacles.

7. How are clouds formed?

Solution:

The process of condensation plays an important role in bringing water back to the surface of the earth. As we go higher from the surface of the earth, it gets cooler. When the air moves up, it gets cooler and cooler. At sufficient heights, the air becomes so cool that the water vapour present in it condenses to form tiny drops of water called droplets. It is these tiny droplets that remain floating in the air and appear to us like clouds.

8. When does a drought occur?

Solution:

If it does not rain for two or more years, water is lost from the soil due to evaporation and transpiration. Since it is not being brought back by rain, the soil becomes dry. The level of water in ponds and wells of the region goes down and some of them may even dry up. The ground water may also become scarce. This may lead to drought.

FUN WITH MAGNETS

 NOTES

Natural Magnet: Magnetite is called natural magnet.

Magnetic materials: The materials which get attracted towards the magnet are known as magnetic materials, e.g., iron, nickel, cobalt.

Non-magnetic materials: The materials which are not attracted towards the magnet are known as non-magnetic materials, e.g., leather, plastic, cloth, paper. Magnetic poles: Magnetic attraction is maximum near the ends of the magnet. These ends are called magnetic poles.

Magnets
Magnets are made of materials that attract objects made of certain substances like iron, cobalt, and nickel.
Magnets come in various shapes and sizes (Fig. 12.1). They can be found as horseshoe, ring, cylindrical, or bar shape.
Not all objects are attracted to magnets. Objects that are attracted by a magnet are said to be magnetic, e.g., iron and nickel. Objects that are not attracted by a magnet, are said to be non-magnetic, e.g., wood and plastic.

Exercise Questions

1. Fill in the blanks in the following

(i) Artificial magnets are made in different shapes such as __________, __________ and ____________.

(ii) The Materials which are attracted towards a magnet are called________.

(iii) Paper is not a ______ material.

(iv) In olden days, sailors used to find direction by suspending a piece of ___________.

(v) A magnet always has __________ poles.

Solution:

(i) Artificial magnets are made in different shapes such as bar magnet, horse shoe and cylindrical.

(ii) The Materials which are attracted towards a magnet are called magnetic.

(iii) Paper is not a magnetic material.

(iv) In olden days, sailors used to find direction by suspending a piece of magnet.

(v) A magnet always has two poles.

2. State whether the following statements are true or false:

(i) A cylindrical magnet has only one pole.

(ii) Artificial magnets were discovered in Greece.

(iii) Similar poles of a magnet repel each other.

(iv) Maximum iron filings stick in the middle of a bar magnet when it is brought near them.

(v) Bar magnets always point towards North-South direction.

(vi) A compass can be used to find East-West direction at any place.

(vii) Rubber is a magnetic material.

Solution:

i) False

ii) False

iii) True

iv) False

v) True (Freely suspended bad magnet)

vi) True

vii) False

3. It was observed that a pencil sharpener gets attracted by both the poles of a magnet although its body is made of plastic. Name a material that might have been used to make some part of it.

Solution:

Iron might have been used to make some part of it.

4. Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.

Column – I	Column – II
N-N	_______
N-___	Attraction
S-N	_____
___-S	Repulsion

Solution:

Column – I	Column – II
N-N	Repulsion
N- S	Attraction
S-N	Attraction
S– S	Repulsion

5. Write any two properties of a magnet.

Solution:

Properties of a magnet are as follows

• It attracts objects made of Nickel, Cobalt and Iron.
• Like poles of two magnets repel each other and opposite poles attracts each other.

6. Where are poles of a bar magnet located?

Solution:

On two ends of a bar magnet.

7. A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole is located?

Solution:

A bar magnet is hanged in the air and the end pointing to the north is the north pole of the magnet.

8. You are given an iron strip. How will you make it into a magnet?

Solution:

Take a bar magnet and keep in contact with one of its poles with one edge of the bar of iron.

• Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end.
• Lift the magnet and bring the pole (the same pole you started with) to the same point of the iron bar from which we began.
• Move the magnet again along the iron bar in the same direction as you did before.
• Repeat this process for about 30-40 times.

9. How is a compass used to find directions?

Solution:

A compass always shows north and south direction, by keeping this as a reference we can always find east and west directions also.

10. A magnet was brought from different directions towards a toy boat that has been floating in water in a tub. Affect observed in each case is stated in Column I. Possible reasons for the observed effects are mentioned in Column II. Match the statements given in Column I with those in Column II.

Column I	Column II
Boat gets attracted towards the magnet	Boat is fitted with a magnet with a north pole towards its head
Boat is not affected by the magnet	Boat is fitted with a magnet with a south pole towards its head
Boat moved towards the magnet when the north pole is brought near its head	Boat has a small magnet fixed along its length
Boat moves away from the magnet when the north pole is brought near its head	Boat is made up of magnetic material
Boat floats without changing its direction	Boat is made up of non-magnetic material

Solution:

Column I	Column II
Boat gets attracted towards the magnet	Boat is made up of magnetic material
Boat is not affected by the magnet	Boat is made up of non-magnetic material
Boat moved towards the magnet when the north pole is brought near its head	Boat is fitted with a magnet with the south pole towards its head
Boat moves away from the magnet when the north pole is brought near its head	Boat is fitted with a magnet with a north pole towards its head
Boat floats without changing its direction	Boat has a small magnet fixed along its length

ELECTRICITY AND CIRCUITS

 NOTES.

Electric current

The flow of electric charges in a circuit is called an electric current. The direction is taken from the positive terminal to the negative terminal of the battery in an external circuit.

Electric Cell

• A cell is a source of electric power, created inside by internal chemical reactions.
• When the chemicals inside the cell are exhausted, the cell needs to be replaced by a new one.
• Cells have two terminals: a positive and a negative terminal. In order for current to flow, the positive terminal must be connected to the negative terminal and this polarity must be maintained.

  Electric circuit

  • A closed-loop path, which the current takes is known as an electric circuit.
  • When the path of the circuit is closed, current flows through it.
  • When there is a break in the path (switch is open) then, the circuit is open and not conducting so the current does not flow.

  

• Conductors and insulators

  • Any material that allows the electric current to pass through it is called as the conductor. Eg: metals like copper
  • Materials that do not allow the free flow of current through it are known as bad conductors or insulators E.g.: Rubber, plastic

@An electric bulb is made up of thin filament which heats up on the passage of electricity and glow .this thin filament is made up of tungsten which has high melting point.

EXCERCISE

1. Fill in the blanks:
(a) A device that is used to break an electric circuit is called_______________
(b) An electric cell has___________
Ans:
(a) switch
(b) two

2. Mark ‘True’ or ‘False’ for the following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermocol.
Ans:
(a) True
(b) False
(c) False.

3.Explain why the bulb would not glow in the arrangement shown in fig

Ans: The bulb would not glow in the arrangement shown in figure because the one end of tester/screw driver is made up of plastic which does not allow the electric current to flow through it.

4. Complete the drawing shown in Fig. 12.9 to indicate where the free ends of the two wires should be joined to make the bulb glow.

Ans:

5.What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
Ans: Electric switch is used to make electric circuit open or closed for a particular appliance and hence with the help of a switch we can use an appliance according

6. Would the bulb glow after completing the circuit shown in Fig. 12.9 if instead of safety pin we use an eraser?
Ans: No, since eraser is an insulator so it does not allow the current to pass. Hence the bulb will not glow.

7. Would the bulb glow in the circuit shown in Fig. 12.11.

Ans: Yes, the electric circuit is closed so the bulb will glow.

Using the“conduction tester” on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
Ans: Yes, if the object is good conductor of electricity then current will pass through conduction tester and the bulb will glow. Hence the object will be a conductor of electricity.

9. Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
Ans: Our body is good conductor of electricity and rubber is insulator. During repairing work if the body comes in contact with current carrying wire then there will not be any accident as rubber does not allow the passage of current through it. Hence electrician uses rubber gloves while repairing an electric switch.

10. The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Ans: Plastic or rubber is an insulator which does not allow electric current to pass through it. The handles of the tools like screwdrivers and pliers used by electricians for repair have covering of plastic or rubber so that electric current may not pass through these tools to the body of the electrician to harm him.

LIGHT SHADOWS AND REFLECTIONS

 NOTES

Source of light: An object which emits light, is called a source of light. For example, sun, torch, etc.

Non-luminous objects: These are the objects which do not emit light of their own. Such a body becomes visible when light falls on it. For example, the moon, the planets, etc.

Ray of light: A straight thin beam of light from a source to an object is called a ray of light.

Obstacle: An object which comes to the path of the light is called an obstacle.

Formation of a shadow

• All the opaque objects seem to form a dark shadow of their own.
• We need a source of light, an opaque object in the way, and a screen to see a shadow.
• Screen: This is a surface on which the shadow is formed. It may be a butter paper or simply ground.
• Shadows give us some information about shapes of objects.
• The colour of the opaque object does not affect the colour of the shadow.
• All the space behind the opaque object, up to some distance behind it seems to be filled with the shadow.

Rectilinear propagation: Light travels in a straight line. It is called rectilinear propagation of light.

Image formation by a plane mirror: We are able to see images through a mirror. Image formed by a mirror (flat) has following features:

• Reflected image retains the colour of the object.
• Image is erect but laterally inverted.

Lateral inversion: Right side of the object appears as left side in the image formed by a plane mirror. For example, if we show our right hand, image in the mirror will show as left hand.

In a mirror, if you see another person, surely the other person can also see you in that mirror.

Luminous: Objects that give out or emit light of their own are called luminous objects.

Mirror: A smooth shining surface, which rebounds the light back in same or in different directions is called a mirror.

Opaque objects: If an object completely stops the passage of all the light falling on it, it is an opaque object.

Pinhole camera: It is a device which forms a photograph-like image of a bright object on a screen.

Reflection of light: When a ray of light falls on a smooth and polished surface, light returns back in the same medium. It is called reflection.

Shadow: Opaque objects do not allow light to pass through them and cast dark patches behind them. These dark patches are called shadows.

Translucent objects: Some objects allow only a part of light falling on them to pass through, such objects are called translucent objects. For example, a single thin sheet of paper.

Transparent objects: Those objects which allow all the light to pass through them are called transparent objects.

Characteristics of a Shadow:
A shadow has the following three characteristics:

• It is always black, regardless of the colour of the object used to make the shadow
• It only shows the shape or outline of the object and not the details.
• The size of a shadow varies depending on the distance between the object and the source of light, and the distance between the object and the screen.

Reflection Surfaces
We say light is reflected when it bounces off a surface. Reflection of light helps us to see most of the things around us.
Reflection of light by a surface depends on the nature of the surface. A rough and bumpy surface (also called an irregular surface) reflects a parallel beam of light incident upon it in different directions (Fig. 13.5). A good example of a rough surface is bark of a tree and blanket. This kind of reflection is called diffused reflection.

A smooth surface (a highly polished surface) reflects a parallel beam of light incident upon it in one direction. (Fig. 13.6). A good example of a smooth surface is a mirror. When you stand in front of a mirror, you can see yourself in the mirror. This is called your image.

NCERT QUESTION ANSWERS AND EXCERCISES

1. Rearrange the boxes given below to make a sentence that helps us understand opaque objects.

Ans:

2. Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the fame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
Ans:

3. Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Ans: Yes, there are many things which give a circular shadow if held in one way and a rectangular shadow if held in another way. For example: a cylinder, a circular disc etc.

4. In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Ans: No, in a completely dark room no image will be formed because there is no light in the room so no reflection of light takes place and no image will be formed.