~Reversible changes
~Irreversible changes
~Physical change
~Chemical change
Oral and Explanation Online with some written work and slides.
1. Reversible changes
2. Irreversible changes
Reversible changes can be described as changes that can be reversed by reversing the action or changing the conditions. Example: freezing of water, rolling of a chapati from dough etc.
Irreversible changes can be described as changes that cannot be reversed even after bringing about changes in the conditions. Example: rusting of iron, cooking of vegetables etc.
Physical change: This represents a change not in the chemical identity but the physical form of a substance. When substances undergo a physical change, there is no formation of a new substance and more or less these changes can be reversed. Example: boiling of water and melting of ice represent reversible physical changes while growing of height is an irreversible physical change.
Chemical change: This represents a change in the chemical identity of a substance. These are irreversible changes because the original substance gets converted into a new substance and cannot be brought back. Example: cooking of rice, burning of matchstick etc.
There are other ways to bring about changes in substances:
Mixing two substances together: A small amount of curd is added to warm milk which leads to conversion of that milk into curd. This is an irreversible change.
When we add a salt to water it becomes salty but this is a reversible change.
Expansion and Contraction: In order to make tools like an axe, the ring of its iron blade is heated which allows it to expand i.e. become larger in size and then is allowed to cool down which makes it contract again i.e. become smaller in size leading to a tight fit of the handle.
Figure 5 Curd is added to milk to allow it to set into curd
To separate two dissimilar but useful elements like in the case of butter and milk. Milk is churned in order to obtain butter.
To segregate useless elements from the useful ones like in the case of separating tea leaves from tea.
To remove and discard impurities or potentially harmful substances like picking out small pieces of stones and other impurities from rice and wheat.
Figure 1 Separating tea leaves from tea
Methods of Separation
Handpicking: The simple process of separating slightly bigger sized harmful substances or other useful substances or impurities like small pieces of stones, husk and dirt from grains of wheat, pulses and rice is called handpicking. In situations when the quantity of such impurities is not very large, handpicking turns out to be a time-saving and convenient procedure of separating substances.
Thus, Threshing can be defined as the process of separating the edible part i.e. grain seeds from the stalk by either with the help of machines, bullocks or sometimes by beating them.
Winnowing can be defined as the method of separating lighter husk particles and heavier grain seed components by blowing a current of air through them. The lighter husk particles are carried away by the wind and the grain seeds get separated. This husk can be further used as fodder for the cattle.
Sieving: Sometimes even after the grain seeds have passed through the stages of threshing and winnowing, husk may still be attached to the grain or it may have collected stones and dirt in the earlier stages which need to be removed and this separation is usually done with the help of a sieve.
Sieving is a very simple, convenient and time-saving process through which particles of varying sizes can be separated from each other with the help of a sieve. A sieve is nothing but a simple device with small pores in it which allow finer materials like flour to pass through leaving behind any impurities it might contain.
Sedimentation, Decantation and Filtration
Sedimentation: Sedimentation can be defined as the process through which dirt and other heavier particles in a mixture settle at the bottom of the vessel when water is added to it. When the dust and dirt particles have settled, the clear water which forms the upper layer is moved to a different container and the dirt and dust is done away with. This technique can also be used to separate two liquids which do not mix with each other (also called immiscible liquids) and is called decantation.
Decantation: Decantation can be defined as a technique through which immiscible liquids or a liquid and a solid substance are separated. For example, take the case of oil and water. These are two examples of immiscible liquids. Once we pour oil in water, oil forms the upper layer of water and can be easily separated by gently pouring the mixture in another container till all the oil has been removed. Sometimes smaller dirt particles get carried along with the water in the process of decantation which needs to be further removed. This can be achieved through the process of filtration.
Filtration: Filtration is the process through which smaller particles like dirt etc. are separated from a solution by making the solution pass through a medium (often a filter paper). This medium is such that only liquids are able to pass through it because of the presence of very tiny pores in it. The filter paper is molded to form a cone and this cone-like structure is then affixed to a funnel through which the dirty solution is allowed to pass. Sometimes, filtration can also be applied to separate pulp and seeds from the juice. It can also be used to separate cottage cheese or paneer from milk.
Evaporation: Evaporation is the process of converting liquid into gas or vapour by increasing the temperature or pressure of the liquid. This process is often used to separate salt from salt water or salty sea water. Sea water has a number of salts present in it. Shallow pits called evaporation ponds are constructed and salt water is allowed to stand in these. After some time, the water gets evaporated, leaving behind the salts. Common salt is separated from this mixture upon further purification.
Often, we are faced with mixtures and solutions that cannot be separated by use of a single separation technique. A number of such techniques need to be applied simultaneously to achieve the desired result.
Take for example the case of a salt and sand mixture. We know handpicking will not work and considering both of them weigh just about the same, neither will winnowing.
And hence we try to separate the two with the help of filtration or decantation.
We take a beaker and add water to the said mixture of salt and sand. While the salt dissolves in water, the sand deposits at the bottom of the beaker and can be separated from the salt solution with the help of a filter paper or by gently pouring the salt solution in another container. We now have to separate the salt from water, for which we will simultaneously use the methods of evaporation and condensation. While heating the solution in a kettle, we observe that vapour or steam starts to rise from the spout of the kettle. What we then do is allow this steam to come in contact with a metal plate which has some ice on it. When this happens, the steam gets converted to small drops of water which we transfer to another container and thus successfully manage to separate salt which gets left behind in the kettle and the water which we collect in a separate container.
Even though water can dissolve a number of substances and solutions in it, it has a limit to how much it can dissolve. After a certain point, it stops dissolving any more of that substance and the substance collects at the bottom of the vessel. We say that the solution has become saturated.
A saturated solution is one that contains the maximum possible concentration of a particular solute. For example, if we continue to add increasing amounts of salt to a small quantity of water, there will come a point that the salt will not get mixed with the water and instead deposit at the bottom. At this point, we say that the solution has become saturated i.e. it is now incapable of dissolving any more of the given solute which is in this case, salt.
A salute is defined as a very small element in a solution that is dissolved in a solution.
One way of ensuring that the given amount of water takes more salt even after it has reached its saturation point is by heating the said water. This is because heating the solution helps to increase the solubility of salt or any solute and hence more amount of the same solute can now be dissolved in the same amount of water.
Some Important Definitions
Churning: The process of shaking milk or cream in order to allow lighter particles to come to the surface in order to make butter is called churning.
Pure Substance: This can be defined as a substance composed of only a single type of particle.
Impure Substance: A substance composed of more than one type of particles.
Sublimation: When a solid directly gets converted into vapour, this process is known as sublimation.
Magnetic Separation: This is another method of separation which allows metals (and other articles which are attracted to a magnet) to be separated from a mixture with the help of a magnetic or by applying a magnetic force to it. For example, a mixture of salt and iron filings can be separated with the help of a magnet.
NOW WATCH THE VIDEOS
Oral and Explanation Online with some written work and slides.
Fig 1: Shows the advancement in transport
Distance: How far an object travels constitutes distance!! The GPS system introduced these days accurately measures the distance from one place to another.
Arbitrary ways to measure the length or width:
Measuring using handspan and measurement by a string were used in ancient times but these methods are not so reliable and hence some standard units of measurement have been introduced.
Fig 2: The Handspan Method
Standard Units of Measurement
Take a thread and tie a knot at one end.
From this end measure a small portion of the curved line which is somewhat straight and put the thumb.
Now again start from the thumb marked position and measure another small portion of the line.
Repeat this process until you reach the end of the line. Tie a knot on the thread on reaching the end. Now measure the two knots using a metre scale.
Oral and Explanation Online with some written work and slides.
We can find many things around us, from mountains and oceans to plants and animals. The earth in which we live is made up of several things. These “things” can be categorized into two different types – Living and Non-living Things.
- All living things breathe, eat, grow, move, reproduce and have senses.
- Non-living things do not eat, grow, breathe, move and reproduce. They do not have senses.
Living things exist and are alive and are made of microscopic structures called cells. They grow and exhibit movement or locomotion. They experience metabolism, which includes anabolic and catabolic reactions.
Living things are capable of producing a new life which is of their own kind through the process of reproduction. Living things have a particular life span and are not immortal.
Examples of living things are animals, birds, insects, human beings.
- Living things exhibit locomotory motion, they move. Animals are able to move as they possess specialized locomotory organs, for example – Earthworms move through the soil surface through longitudinal and circular muscles. Plants move in order to catch sunlight for photosynthesis
- Living things respire. Respiration is a chemical reaction, which occurs inside cells to release energy from the food. Transport of gases takes place. The food that is ingested through the process of digestion is broken down to release energy that is utilized by the body to produce water and carbon dioxide as by-products.
- Living things are sensitive to touch (and other stimuli as well) and have the capability to sense changes in their environment.
- They grow. Living things mature and grow through different stages of development.
- One of the striking features is that living things are capable of producing offsprings of their own kind through the process of reproduction, wherein genetic information is passed from the parents to the offsprings.
- They acquire and fulfil their nutritional requirements to survive through the process of nutrition and digestion, which involves engulfing and digesting the food. Some living organisms are also autotrophic, which means they can harness the sun’s energy to make their food (also known as autotrophs).
- The digested food is eliminated from the body through the process of excretion.
Non-living things are not alive. They do not possess life. They do not have cells and do not grow or show locomotion/movement. They do not undergo metabolism with anabolic and catabolic reactions. They do not reproduce.
Non-living things do not have a life span. They do not respire as they do not require food for energy and hence do not excrete. They do not fall into any cycle of birth, growth or death. They are created and destroyed by external forces.
Examples of non-living things include stone, pen, book, cycle, bottle, etc.
Characteristics Of Non-living Things
The important characteristics of non-living things are mentioned below:
- Non-living things are lifeless. They do not have cells, and there is no protoplasm which forms the basis for life to exist.
- Lack of protoplasm leads means no metabolic activities.
- They do not have a definite and certain size of their own. They take the shape of the substance they are contained in, for example, a liquid takes the shape of its container. Stones, rocks and boulders are moulded by the changing environment and landscape. The change in the state of a non-living thing is due to an external influence.
- Non-living things “grow” by accretion. It occurs through adding materials externally. For example, A snowball may increase in size due to the accumulation of smaller units of its own to its outer surface.
- Non-living things never die as they do not have cells with a definite lifespan. Immortality is a distinguishing factor.
- Fundamental life processes such as reproduction, nutrition, excretion, etc. are absent in non-living things.
Here are some of the major differences between living and non-living things:
| Living Things | Non-Living Things |
| They possess life. | They do not possess life. |
| Living things are capable of giving birth to their young one. | Non-living things do not reproduce. |
| For survival, living things depend on water, air and food. | Non-living things have no such requirements |
| Living things are sensitive and responsive to stimuli. | Non-living things are not sensitive and do not respond to stimuli. |
| Metabolic reactions constantly occur in all living things. | There are no metabolic reactions in Non-living things. |
| Living organisms undergo growth and development. | Non-living things do not grow or develop. |
| They have a lifespan and are not immortal. | They have no lifespan and are immortal. |
| Living things move from one place to another. | Non-living things cannot move by themselves. |
| They respire and exchange of gases takes place in their cells. | Non-living things do not respire. |
| Example: Humans, animals, plants, insects. | Example: Rock, pen, buildings, gadgets. |
Complete all the questions given below in your OCB (Online Class Ex-books)
A. Choose the correct option in the following
- The tiny pores present in the leaves.
- The process of taking food by organisms.
- The process of getting rid of wastes.
- The process of removal of wastes in plants.
- The factors like food, water, light, temperature to which organisms respond.
- Production of new organisms of own kind.
- Increase in the size along with mass using energy.
Oral and Explanation Online with some written work and slides.
WHAT PEOPLE WORE
Yarn: Yarn is defined as a long, twisted and continuous strand composed of interlocked fibres or filaments which are used in knitting and weaving to form cloth.
Fibres: The thin threads or filaments which form a yarn are called Fibres.
Where do fibres come from?
Fibres can be broadly classified into two broad categories:
Natural Fibres: Fibres that come from plants and animals i.e. are found in nature are called Natural Fibres. Examples:
We get jute and cotton from plants.
Wool is acquired from the fleece of a goat or sheep. It can also be acquired from the hair of yak, rabbits and camels.
Silk fibre can be procured from the cocoon of silkworms.
Synthetic Fibres: Fibres that are made of chemical substances i.e. substances not found directly in nature are classified as synthetic fibres. Examples include nylon, acrylic and polyester.
1. Cotton
A field of cotton
Where does cotton wool come from?
Cotton plants are grown in fields usually at places having a warm climate and black soil.
Some cotton producing Indian states are Punjab, Gujarat, Madhya Pradesh, Karnataka, Maharashtra etc.
Cotton plants bear fruits the size of a lemon called Cotton Balls which burst open upon maturing and the seeds wrapped up in cotton fibre become visible. Cotton is generally picked by hand from these balls.
Ginning: Ginning of cotton can be defined as the process of separating cotton fibres from cotton seeds. Traditionally, ginning used to be done by hand but these days machines called double roller cotton ginning machines are widely in use.
In the above figure, we see a boy ginning by hand.
2. Jute
A jute plant
Jute fibre is obtained from the stem of the plant.
Unlike cotton, jute is cultivated in the rainy season.
Some jute producing Indian states are Bihar, Assam and West Bengal.
The plant is harvested during its flowering stage.
The stems of these harvested plants are then soaked in water for four to five days
The stems are left to rot and then the fibres are picked out by hand.
Yarn: Yarn is the spun thread that is made from fibres in order to produce a fabric.
Spinning Cotton Yarn
Spinning: Spinning is the process of constructing yarn from fibres in which fibres from a huge heap of cotton wool are taken out and twisted which brings them together to form a yarn.
There are two major devices called Takli which is a hand spindle and Charkha which is also a hand-operated device, are used for spinning.
The spinning of yarn on a bigger scale is done using spinning machines following which these yarns are used to weave fabric.
Khadi was the term used to denote clothes which were made from homespun yarn.
On the left we can see a charkha and on the right we can see a simple takli.
Yarn to Fabric
There are two major ways using which yarn is converted to fabric, namely, Weaving and Knitting.
Weaving: The process of entwining two sets of yarn simultaneously to make fabric is called Weaving. The process is done using a loom (which can either be operated by hand or by a machine) which interlaces two sets of yarn at right angles to each other.
The above figure represents the process of weaving.
Knitting: Knitting is the process by which a single strand of yarn is used to make a piece of fabric. Socks, sweaters, mufflers and a lot of other winter clothes are made of knitted fabrics. Knitting can be done by hand as well as by machines.
History of Clothing Material
In earlier times, when people did not have access or the knowledge to process fibre, big leaves and the bark of trees were used by people to cover themselves.
After settlement began in agricultural communities, they learnt how to weave. They used grass and twigs to make mats and baskets. Animal hair or fleece and vines were warped together into stretched out strands which were then woven into fabrics.
There was an abundant growth of cotton in areas near Ganga, which the early Indians readily used to make fabrics for themselves.
There is another plant named flax which yields natural fibres.
The early Egyptians cultivated both cotton and flax and used them for creating fabrics. These plants grew near the river Nile.
But in those days, people were not aware of the process of stitching. They simply used to wrap around the fabric around different parts of their bodies. Even today unstitched clothes like sarees, dhotis, lungis or turbans are widely in use.
It was with the advent of the sewing needle that people learnt how to stitch fibres to make fabric.
Oral and Explanation Online with some written work and slides.
Oral and Explanation Online with some written work and slides.
How are living beings different from non-living things ?
Certain criteria’s can differentiate living beings from non living things-
1. Need of food
- Like all animals; plants also need food for growth and development which they prepare by photosynthesis.
- But non-living things do not grow and thus do not need food.
- All livings beings grow and show different stages of growth.
- Young ones of animals grow into adults. For example- Pups of a dog grow into adults,chicken from a hatched egg grows into a hen or a cock.
Fig. Young ones of a hen grows into adult
3. Respiration –
- The process of breathe in oxygen and using by the body to obtain energy and releasing carbon dioxide produced in this process is called respiration.
- Breathing is a part of respiration.
- Different organisms use different ways to exchange gases. For example- earthworms breathe through air, fishes through gills , plants by the tiny pores present in the leaves.
- In sunlight, plants take carbon dioxide to produce food and release oxygen. This process is called photosynthesis.
- Photosynthesis in plants take place only during day time but respiration takes place day and night.
- Non living things do not breathe and hence do not respire.
4. Response to stimulus-
- Any change in the external environment is called stimuli and reaction of organisms against the stimulus is called response.
- Examples- Shut down of eyes in bright light, Running away of wild animals in response to bright light, Blooming of plants only after sunset, Folding of touch me not plants when touched
- But non-living things do not show any response against stimulus.
Fig. Blooming of plants at night
5. All living organisms excrete-
- Digestion of food takes place inside the body and used by the cells but undigested food remains as waste.
- The process of removal of waste from the body is called excretion.
- Excretion is shown by all plants and animals, some plants can store the waste as harmless products and some plants use the method of secretion to excrete the waste.
6. Reproduction-
- The process of giving rise to the young ones is called reproduction.
- Some animals produce young ones through eggs and some give birth.
- Some plants reproduce from seed which germinates and grow into a new plant.
- Some plants reproduce through other parts of the plant body. For example, a part of a potato with bud can give rise to a new plant.
- Some plants reproduce through cuttings in the plant body.
- All non-living things are man-made and thus cannot give rise to the new one.
Fig. Reproduction gives rise to similar young ones of human and monkey
7. Movement-
- All living beings can move from one place to another except plants.
- Plants cannot move from one place to another because these are anchored in soil by roots, but minerals, water and foods present in the plant move from one part to other parts of the plant.
- Closing and opening of flowers of a plant is another phenomenon which shows that plants can move.
- Non-living things are constant in their places where they are kept and hence cannot move.
Fig. Running of a cat, flying of birds show movement of living beings.
- Bus, clocks, clouds can also move but these do not show other characteristics of living beings so these are non living.
Fig. A tiger, flowers, a cat represent living beings
Fig. A clock, a car, a monument represent non-living things
- A moong seed can stay in a shop for months but do not show characteristics of life. After planting and watering it turns into a whole plant. This shows that in some cases a thing has all characteristics of living being but we cannot easily say it living.
Fig. Moong seeds
- Dipping hand inside a sack of wheat gives a feeling of heat production which is due to respiration but other criteria’s to become a living being are not found.
- Cloud shows movement and also grows in size but other features to become a living being are absent.
Deciding living or non living is really difficult but seeing at the diversities of life it can be concluded that life is beautiful.
Oral and Explanation Online with some written work and slides.
Oral and Explanation Online with some written work and slides.
Plants are a source of a wide variety of nutrients required to keep the human body in perfect working condition. Humans get everything from fruits, flowers, even the stem of some plants, leaves and stem-like lettuce, celery, roots of some plants like carrots, beetroot, and seeds like wheat, rice, etc. All the food that is consumed comes from plants, even the animals depend on plants. Hence, it can be concluded that we obtain food from plants directly or indirectly. The reason one is advised to consume fruits and vegetables on a daily basis is that it is a source of rich nutrients.
Vegetables, coffee, cereals, pulses, fruits, sugar, spices, oil, etc. can be obtained from plants. Let's have a look at the different types of plants food source -
Vegetables are obtained from the plants. Some nutrient-rich vegetables such as beetroot, turnip, spinach, cauliflower, etc. are obtained from plants. Roots, leaves, and stems of some plants are edible.
Radish, turnip, carrot, beetroot are some of the roots that are eaten as vegetables.
Potato and ginger are the stems that are eaten as vegetables.
Spinach, cabbage, lettuce are the leaves eaten as vegetables.
Broccoli and cauliflower are the flowers eaten in the form of vegetables.
Fruits
Fruits are a perfect example of a healthy source from plants. We get fruits like orange, mango, apple and other fruits consumed by humans.
Oil
Oil can be extracted from the seeds and leaves of the plants. Some of the plants producing oil are castor, mustard, and sunflower.
2. Food From Animals
Animal products are a rich source of nutrients. The food chain is made up of exactly these animals starting with organisms that use the energy of the sun to the end by which the organisms are predators and rely on producers.
Let's have a look at the different types of animal products consumed for their nutritional benefits -
Cows, buffaloes, sheep, goat, and camels are a great source of milk. Milk is also called as an ideal food. It is rich in vitamins, minerals, proteins, carbohydrates, and fats.
Chickens, ducks, geese, and quails are raised for eggs and meat. The egg is a rich source of protein and vitamin. The yolk of the egg is mostly made up of egg. It also contains vitamins, phosphorus, calcium and iron.
Meat is of two types- red meat and white meat.
The meat of cow, goat, sheep and pigs has a lot of fat and is called red meat. White meat contains less fat and is obtained from chicken and fish. White meat is healthier and can be easily digested as compared to the red meat. Meat is rich in proteins, vitamins, zinc, phosphorus and iron.
1. What is a balanced diet? What should it contain?
2. Why is it important to include roughage in diet?
3. What are deficiency diseases? What happens to children who do not get enough to eat?
4. Describe how vegetables reach our homes from the field where they are grown?
Oral and Explanation Online with some written work and slides.
