The amount of oxygen decreases at high altitude. So, for normal breathing, mountaineers carry oxygen cylinders with them, while climbing high mountains.

The part of skeletal system that is inside the body and covered by soft tissues is endoskeleton. It cannot be seen from outside. One can feel or see it through X-ray photography only.

(i) Light helps us to see an object.
(ii) It converts chemical energy into light energy.
(iii) The values exhibited by Ravi are caring, love and presence of mind.

(a) Growth of plant-Irreversible change.
(b) Falling of rain-Irreversible change

(a) Eyes of the deer are located on the sides of its head. This helps it to see in all the directions.
(b) Exchange of gases in an earthworm takes place through its moist skin

If we make a metal red hot, it emits light. This is called incandescent body

A saturated solution of a substance is the one in which no more of that substance can be dissolved.

By measuring distance by a particular standard unit of measurement.

Yes

It is a thick paste made up of clay, paper pieces and some rice husk.

The ocean water contains high concentration of different salts rendering the water salty making it unfit for use.

Mustard oil and kerosene oil are the two liquids which are insoluble in the water.

Black soil is best for the cultivation of cotton crop.

Anther and filaments are male reproductive parts of a flower.

Yes, it can be very harmful to eat too much fat rich foods. Unused fats get deposited in our body.

Yes, sprouting of pulses can be done. In this form, pulses are highly nutritious.

We notice tiny water droplets, i.e., dew on leaves or metal surfaces like iron grills and gates on a cold morning.

The cells used in calculators are known as button cells, as they resemble the shape of a button. The plates of these cells are made from compounds of nickel and cadmium. The main advantage of these cells is that they can stay in an active stage for months without any leakage.

Sea water is allowed to stand in shallow pits. Due to solar heat, water in the pits get evaporated. After some days, the water evaporates completely and the solid salts remain in the pits. These salts are further purified to get pure common salt

(a) Land-motorcycle, car.
(b) Water-Boat, steamer.
(c) Air-Aeroplane, helicopter.

As, we know that like poles of a magnet repel each other and unlike poles attract each other.
Thus, the complete table is shown as below:

(a) We usually throw the left over food at home. But it is a biodegradable waste which can be converted into useful products by microorganisms.
So, left over food at home should be dumped into compost pits to convert them into manure. This manure can be used for growing plants.
(b) We will prefer a banana leaf platter because it is biodegradable and can be disposed easily. By the process of composting, it can be converted into manure, while a plastic plate is non-biodegradable and has a lot of difficulty in disposal. It also causes pollution.

Following are the non-living things from the list which were once part of living things:
Butter - Obtained from milk from dairy animals
Leather - From animal skin
Wool - From hair of sheep or goat
Cooking oil - Seeds of plants
Apple - Fruit from apple tree
Rubber - Latex of rubber tree

(a) Mask is covering the nose and mouth of the policeman.
(b) Policeman is putting a cover on his nose to save himself from dirt/polluted air.
(c) Air quality of the place is not good. It is due to the smoke and gases emitted by the automobiles along with dust particles present in the air.

Position A of the torch will form the image (a) and position B of the torch will form the image (b) of the football.

A muscle can only pull, it cannot push. Thus, two muscles are required to work together to move a bone. When one muscle contracts, bone is pulled. When another muscle of the pair pulls, it brings the bone in its original position.

(a) Objects or materials which are in the form of circle, are known as round shapes.

(b) The substances which we can eat, are known as eatable otherwise it is known as non-eatable.

Stems are modified to perform special functions. One of such function includes making of food. In some plants like cactus, fleshy stem is found which can perform the process of photosynthesis.

No, the changes which have occurred in the cement cannot be reversed because it is a irreversible chemical change.

Two items that are made from coconut fibre are
(i) Ropes
(ii) Mats

The drops of iodine are used to detect the presence of starch in the food item. The possible reason for appearance of blue-black colour on teacher's saree is due to the presence of starch. The saree would have been starched. Paheli's socks did not have starch on it, thereby their colour did not change.

The plant A is banana whose fruit is eaten raw and flowers are cooked as vegetable. The plant is B mustard. Its seeds are used to make mustard oil whereas its leaves are cooked to make green vegetable called 'sarson ka saag'.

There are following properties by which we can prove that these materials are different:

Cockroaches walk and climb as well as fly in the air. They have three pairs of legs which help them in walking. The body is covered with a hard outer skeleton. This outer skeleton is made of different units joined together which permit movement. There are two pairs of wings attached to the thorax. The cockroaches have distinct muscles-those near the legs move the legs for walking. The thoracic muscles move the wings when the cockroach flies.

Cactus is mostly found in the deserts.
It has the following special features to adapt itself to survive in the desert :
(i) Leaves are modified into the spines to reduce the rate of loss of water.
(ii) Stem becomes green and fleshy to take over the function of photosynthesis.
(iii) Stem is also covered with a thick layer of wax to retain water.
(iv) Its roots go deeper into the soil for better absorption of water.

Characteristics of plants are :
(i) They cannot move from one place to another.
(ii) They can prepare their own food.
(iii) These are the living organisms on the earth which are responsible for the formation of food for all the living forms directly or indirectly.
(iv) All other organisms on the earth depend on the plants and their products for their survival.
(v) Plants grow in the soil from where they take nutrients for their growth and propagation.

Water is used:
(i) for drinking and cooking
(ii) for bathing and cleaning.
(iii) in agriculture, to produce food.
(iv) in Industries, to perform different activities

To find out the magnet
(i) Take the bar magnet A in your hand.
(ii) Take the bar magnet B in other hand.
(iii) Bring one side of B towards South pole and note down it is attracted or repelled.
(iv) Bring other side of B towards South pole and again note down the same thing.
(v) If there is an attraction in both cases (iii) and (iv), then it is definitely an iron bar.
(vi) If there is an attraction in one case and repulsion in other case, then it is a bar magnet.
(vii) Do the same for the iron bar C.
To find out the poles:
If in case (iii) the bar is attracted, then it is North pole of the identified bar magnet. If bar is repelled, then it is obviously a south pole of the identified bar magnet.

(a) Papers are biodegradable wastes.
(b) Rahul used recycling of paper by making papier mache.
(i) use the materials again. (ii) reduce wastage,
(d) No, shiny paper contains plastic. hence they cannot be recycled.
(e) Rahul is thoughtful. creative and eager to use his knowledge.

An electric torch is a device which is used as a lamp. It has two or more than two cells, a bulb and a switch.

So, when we slide the switch of electric torch, circuit becomes complete and bulb starts glowing, while on sliding switch back, circuit gets broken and bulb goes OFF.

(a) There will be no life on the earth. Oxygen is vital for life. It helps in burning, respiration, photosynthesis, etc. Oxygen is basic need of all living beings.
(b) Nitrogen does not support burning. If nitrogen gas disappear from the atmosphere, things will burn very fast.
(c) Carbon dioxide is needed for photosynthesis which occurs in green plants. In its absence, plants will not be able to prepare their food and hence, there will be no life on the earth.

Yes, the shadow will be formed in all the cases but in all the cases, the darkness of the shadow will be different.
(i) Most of the light in case of transparent sheet will pass through the glass. So, the darkness of shadow will be very low.
(ii) Also most the light in case of muslin cloth will be reflected. So, the shadow will be darker than the transparent sheet.
(iii) While in case of plywood, all the light would be stopped completely by the plywood. So, the darkness strength will be highest in this case.

Elastic tapes are stretchable due to which their length can be increased during the measurement if it is not handle with care. Therefore, the measurement done by elastic tapes may be greater than the actual length of the object. So, we can say that elastic tapes are not accurate to measure a length.

Reversed changes are as follows:
(a) Simba blew balloons and put them on the wall.
(d) Making of some flowers by origami (paper folding) to decorate the house.
(e) Her father made dough balls.
(f) Mother rolled the dough balls to make puries.
(g) Mother heated oil in a pan.
Changes that cannot be reversed are as follows:
(b) Some of the balloons got burst.
(c) Paheli cut colourful strips of paper and put them on the wall with the help of tape.
(h) Father fried the puries in hot oil

Cotton is the most important of all plant fibres, used to make clothes.Cotton shirt can be prepared by following steps:
Cotton bolls \(\underset { \xrightarrow{}}{ Ginning } \) Cotton fibre \(\underset { \xrightarrow{}}{ Spinning } \) Cotton yarn \(\underset { \xrightarrow{}}{ Weaving} \) Cotton fabric \(\underset { \xrightarrow{}}{ sewing} \) Cotton shirt
The making of cotton shirt is a long process. From cotton bolls, cotton is usually picked by hand. Fibres are then separated from the seeds by combing. This process is called ginning.
In spinning process, the fibres from a mass of cotton wool are drawn out and twisted. This brings the fibres together to form a yarn.
Weaving is binding of two sets of yarns at right angles to make a fabric. Weaving is done on looms. Now, on sewing this cotton fabric by needle, we get the cotton shirt.

Paheli can make this water fit for drinking by work on following sequence:
Filtration using muslin cloth (cotton fabric).
                         \(\downarrow\)
Swirl with alum and leave water undisturbed for some time.
                          \(\downarrow\)
The clear liquid above the impurities is poured in another container(decantation).
                           \(\downarrow\)
Boil for 10 min in covered pan with lid.
                           \(\downarrow\)
Cool, filter and now, it is fit for drinking.

(a) Many vegetables contain most of the nutrients just below their skin surface. Thick peeling may lead to their removal.
(b) Washing of vegetables after peeling or cutting removes the water soluble vitamins and minerals from them and lowers their nutritive value.
(c) These components are called nutrients like minerals (iron, calcium, phosporous) and vitamins (B, A, C, D, E).
(d) Vegetables like tomatoes, potatoes, green leafy vegetables, etc.
(e) Yes, Radha is sincere, observant, helpful and knowledgeable. She used her knowledge in right place and stopped her mother for doing incorrect work.

(a) Yes, without food there is no energy in people and their body cannot fight against infections.
(b) Food is required because it gives us energy to carry out all life processes.
 It helps in growth and maintenance of body.
(c) Malnutrition.
(d) Ashu is sincere, caring and a helpful boy. He is eager to provide his support and encourages his friends in helping him to help villagers.