class 10th Science cbse ncert notes

The process in which a substance goes under chemical change and new product or producs are formed is called chemical reaction.In other words, changes in chemical nature of substance generally denote the chemical reaction.

In a chemical reaction changes take place are: (a) Change in nature of substance. (b) Formation of new product.

Chemical reactions are generally irreversible in normal conditions. All chemical changes denote the taking place of chemical reaction. . .

Living organisms move in the response to change in the environment. Living organisms move to get advantage of the change. Getting advantage of change in environment is necessary for organisms to survive. Movement in the response to change in environment is called stimuli. For example, a cat may jump or start running after seeing a mouse to catch it to satisfy its hunger. On the other hand mouse flees after seeing a cat to protect itself, a plant grows out in sunshine, We drive our hand away as we touch a hot object.

All these types of movements are not taken place in haphazard manner. Rather all these movements are controlled and coordinated properly. Movements made by living organisms depend on the event that triggered it. Such controlled movements are connected to the recognition of various events in the environment followed by only the correct movement in response. . .

Taste of foods makes our life tasty. Every food we eat has some taste. Those tastes are sour, sweet or salty. Some food items have bitter taste because of base present in them. Cold drinks taste slightly bitter because of presence of base in them.

Acids : Acids are sour in taste. Food items having acids are sour in taste. For example Lemon, curd, tamarind, curd, unripe fruits etc. are some most common food items that are used in households. As these items contain acids, hence these are sour in taste.

Chemical substances that are detected commonly by their sour taste are called ACIDS.

On the basis of occurrence Acid can be divided into two types: these are Natural acid and Mineral acid . . .

Substances can be divided into two types on the basis of some properties. These types are Metals and Non-metals.

Metals are hard, lusturous, sonorous, malleable, ductile, good conductor of heat and electricity. Along with these metals have high melting and boiling point. For example, iron, copper, alulminium, gold, silver, etc.

Metals are solid at room temperature, however mercury is the only metal which is liquid at room temperature.

On the other hand Non-Metals are soft, non-lustrous, non-sonorous, non-malleable, brittle, bad conductor of heat and electricity and have low melting and boiling points. For example, carbon, oxygen, chlorine, bromine, fluorine, etc. . .

Electricity is a type of energy that can be controlled and used to make our life comfort. Flow of water through a water body, such as river, ocean etc. is called water current. Flow of wind is called wind current. Similar to that electric charge flows through a conductor and this flow of electric charge is called electric current.

Substances which allow the flow of electric charge through them are called conductor and metals are good conductor of electricity. This means metals allow flow of electric charge through them. That's why electric wires are made of metals.

According to some Egyptian Texts of about 2750 BC back, people were aware about electric current. People know about a type of fish which gave shock. Such fish were called 'THUNDER OF NILE' and were considered as protector of fish. . .

When a compass is brought near an electric current carrying conductor, the needle of compass gets deflected; this happens because of magnetic field produces by electric current. This phenomenon is called magnetic effect of electric current.

Electricity and Magnetism are related phenomenon. This was first observed by Hans Christian Oersted, a Danish scientist in 1820. In his honour the unit of magnetic field strength is named as Oersted.

Direction of the magnetic field associated with a current carrying conductor can be understood easily with Right-Hand Thumb Rule.

Right – Hand Thumb Rule states that if one holds a straight current carrying conductor with right hand such that the thumb points towards the direction of current, then fingers will wrap around the conductor in the direction of field lines of the magnetic field. . .

Capacity of doing work is called energy. We use our muscular energy to do many works. Apart from that we use many natural sources of energy, for example burning of wax is used in candle to get light. Burning of diesel or petrol is used to run vehicles.

One form of energy can be converted into other form, for example to lit an electric torch we convert chemical energy into light energy.

There are many sources of energy we have, such as fossil fuels, wood, solar energy, wind energy, water energy, etc. which we use to make our life comfortable.

Fossil Fuels are one of the most used sources of energy. Many millions of years ago living organisms, such as trees and plants, got buried. Over the time period because of anaerobic decomposition dead organisms were converted into forms sources of energies. These sources of energy are called FOSSIL FUELS.

Coal, petroleum and natural gases are example of fossil fuels. Today human depends almost completely on these fossil fuels to get energy. . . .

Light travels in straight line. An opaque object obstructs rays of light when it comes in the path of light, and casts a shadow, this phenomenon tells that rays of light travels in straight line.

When rays of light fall on an object, they bounce back and come to our eyes. Bouncing back of light after falling on an object to our eyes enables us to see a particular object. We cannot see an object in dark, because there is no light present in dark which can be bounced back to our eyes.

Bouncing back of rays of light from an object is called the REFLECTION OF LIGHT.

A highly polished surface reflects most of the light falling on it. For example a mirror, which has polished surface, reflects most of the light falling on it. . . .

Carbon is the 15th most abundant element in earth's crust and fourth most abundant element in universe by mass after hydrogen, helium and oxygen. Carbon constitutes of only 0.2% of earth's crust and only 0.03% of carbon compound in the form of carbon dioxide present in atmosphere. Inspite of this small amount of carbon available in nature, carbon plays very important role in our life.

Carbon is the common element found in all known form of life. Structure of all living organism contains carbon. Carbon present in living organism even after death. Coal, petroleum and its products are compounds of carbon. Carbon is an element and a non-metal.

Carbon has two unique properties, i.e. tetravalency and catenation. Because of these properties carbon forms a large number of compounds. There are more than three million compounds of carbon known so far. . .

No organism survives forever and therefore, if a species is to continue to exist, its members must reproduce their own kind. Hence, all the living organisms reproduce their own kind to maintain the continuity of their race. Reproduction therefore, helps in the increase in population of the species. It transfers the characteristics of parents into offspring.

The process by which living organisms produce new individuals similar to themselves is called REPRODUCTION. It is one of the most important characteristics of living organisms as it ensures perpetuation and survival of a race. The process of reproduction has ensured continuity of life on earth.

There are two basic types of reproduction: Asexual Reproduction and Sexual Reproduction

When reproduction occurs without the fusion of gametes, it is called Asexual Reproduction. In Asexual Reproduction a single organism is capable of producing its own kind. . .

With the increasing number of discovery of elements, scientists started to need their classification. Periodic Table is a tabular compilation in which elements are arranged according to their unique properties.

There are two types of Periodic Tables laid the milestone in the classification of elements. First is the Mendeleev's Periodic Table and second is the Modern Periodic Table or Long form of Periodic Table.

In the Mendeleev's Periodic Table elements are arranged in increasing order of their atomic mass. And in the Modern Periodic Table elements are arranged in the increasing order of their atomic number. . .

Eye is one of the most important sense organs. It is the eye which enables us to see and understand the colourful world around us. There are many persons who cannot see and are called blind.

Eye works like a camera, rather camera was invented after observing the working pattern of eye and it can be said that camera works like an eye.

The structure of human eye is similar to a spherical ball. Light coming from an object enters into eye ball through the lens and cast the inverted image at retina, which is a light sensitive screen located at the back portion of the eye ball. Optic nerves send this image to the brain which interprets the correct picture and we see the object or anything.

Eye ball, Cornea, Iris, Pupil, Lens and Retina are the main parts of an Eye. . .

The branch of science which deals with the transmission of characters from one generation to another is known as heredity and it can be defined as the science which deals with the inheritance of characters from one generation to next generation or from parents to offspring.

Variation is the differences in the trait among the organisms of a species. An offspring does not exactly resemble to either of its parents. It receives 50% of its characters from father and 50% from mother. Parents may differ in many characters like height, skin, color, eye color, types of hair, shape of nose, chin and so many other characters. All these differences are called variations.

These variations are also observed in animals and plants. The greatest advantage of variation in a species is that they increase the chances of survival in a changing environment. . .

Question (1) Reema took 5 ml of Barium Chloride solution in a beaker and added approximately 4 ml of Potassium Sulphate solution to it. What would she observe?

(A) The solution turned red.

(B) Yellow precipitate was formed

(C) White precipitate was formed.

(D) The reaction mixture became hot.

Answer (C) White precipitate was formed.