NCERT Solutions for Class 9 Science

NCERT Solutions for Class 9 Science is prepared by experts of HT and all the questions asked in the NCERT textbook are solved with proper explanation of all points given in the theory part of the textbook to score good marks in school exams. We provide the best and most detailed NCERT solutions for class 9 Science subjects!

Do you look for detailed solutions in your NCERT books?

NCERT 9th Grade Science solutions help students eliminate any doubt quickly and effectively. These NCERT Solutions guide students to learn key concepts in the CBSE Class 9

Science syllabus. Students need to solve the exercise questions included in the book to build a proper understanding of the topics. HT experts prepared NCERT Solutions all the questions asked in the NCERT exercise are solved as per the CBSE school Requirements do check NCERT Solutions for class 9. 

NCERT complete solution for class 9 Science

While the textbook questions are being resolved, doubts among students arise that lead to later confusion. NCERT Solutions for Class 9 comes in handy at such times, as it incorporates precise explanations and detailed answers to those questions. These CBSE Science NCERT Grade 9 solutions include solutions for all the important chapters in the textbook, such as Matter, Atom, Tissues, Living Organisms, Motion, Force, Laws of Motion, Gravitation, Energy, and Work, Sound, Natural Resources, etc.

You can look for the solutions in the PDF provided on our website. Our qualified experts well design these.

Here are Important chapters Wise introduction of NCERT Solutions for Class 9 Science:

Here, we are providing the complete chapter-wise NCERT Solutions for Class 9 Science. Keeping in mind the language barrier, we have provided these solutions in two languages: English and Hindi.

A brief introduction to a few chapters of NCERT solutions for class 9 science

• NCERT Solutions for Class 9 Science Chapter 4 Structure of the Atom

The first useful theory about the atom was put forward by John Dalton in 1808.

• The main postulates of Dalton’s atomic theory are:

1. The matter is composed of tiny individual particles called atoms.
2. Atom cannot be created nor be destroyed, or transformed into atoms of another element.
3. Atoms of a given element are identical in all respects. Atoms of different elements are different from each other.
4. Atom is the smallest particle of an element which takes part in a chemical reaction
5. Atoms of different elements combine in a fixed ratio of small whole numbers to form compound atoms, called Molecules

• NCERT Solutions for Class 9 Science Chapter 5 The Fundamental Unit of Life

The history of biology traces the study of the living world from ancient to modern times. Although the concept of biology as a single coherent field arose in the 19th century, the biological sciences emerged from traditions of medicine and natural history reaching back to Ayurveda, ancient Egyptian medicine.

1. Cells form the basis of all living things. They are the smallest single unit of life, from the simplest bacteria to blue whales and giant redwood trees. Differences in the structure of cells and the way that they carry out their internal mechanisms for the basis of the first measure division of life, into the three kingdoms of Archaea (ancient bacteria, Eubacteria (modern bacteria) and Eukaryote (everything else, including us). An understanding of cells is therefore vital in any understanding of life itself
2. Cell biology (formerly cytology, from the Greek ketos, "contain") is a scientific discipline that studies cells – their physiological properties, their structure, the organelles they contain, interactions with their environment, their life cycle, division and death. This is done both on a microscopic and molecular level. Cell biology research encompasses both the great diversity of single-celled organisms like bacteria and protozoa, as well as the many specialized cells in multicellular organisms such as humans, plants, and sponges.

Knowing the components of cells and how cells work is fundamental to all biological sciences. Appreciating the similarities and differences between cell types is particularly important to the fields of cell and molecular biology as well as to biomedical fields such as cancer research and developmental biology. These fundamental similarities and differences provide a unifying theme, sometimes allowing the principles learned from studying one cell type to be extrapolated and generalized to other cell types. Therefore, research in cell biology is closely related to genetics, biochemistry, molecular biology, immunology, and developmental biology.

• NCERT Solutions for Class 9 Science Chapter 6 Tissues

The higher plants and animals have highly complex bodies made up of various kinds of cells. These groups or clusters of cells are called tissues. Tissues improve the efficiency with which the body functions by allowing division of labour, that is, sharing of tasks. Each tissue is specialized for a particular job.

Thus, a tissue can be defined as a group of similar or dissimilar cells of common origin that perform or help to perform a common function.

The term ‘tissue; was coined by N.Grew and was referred to as animal tissue too by a French biologist Bichat. The study of tissue is called histology. How does a whale survive in cold water?

The poison dart frog is the most poisonous. Which tissue is responsible for the secretion of toxins?

TISSUES

Introduction:

• The study of tissues is known as histology.
• The concept of histology includes understanding the structure of cells, tissues, organs and organ systems, which can better be described as Microscopic Anatomy.
• Marie Xavier Bichat is known as the father of modern histology and pathology.
• He worked without a microscope and first introduced the notion of tissues.
• He maintained that diseases attacked tissues rather than organs.

Xavier Bichat

Tissue

Nehemiah Grew: (1641-1712) was an English plant anatomist and physiologist. His great work on the anatomy of plants appeared in 1862. It was divided into four books: Anatomy of vegetable, anatomy of roots, Anatomy of trunks, and Anatomy of leaves, flowers, Fruits and Seeds. The anatomy of plants is especially notable for its descriptions of plant structure. He described nearly all key differences in the morphology of stem and root, showed that the flowers of Asteraceae are built of multiple units, and correctly hypothesised that statement is male organs. The anatomy of plants also contains the first known microscopic description of pollens. Linnaeus named a genus of trees Grewia in his honour. He is called the father of plant anatomy.

1. In multicellular organisms there is a division of labour.
2. A group of cells that are specialized to carry out functions effectively.
3. Tissue is a group of cells similar in structure and function. Various tissues of an organism work in co-ordination with each other to perform various functions
4. In plants and animals tissue are found but these tissues have differences in various aspects which are the following:

• NCERT Solutions for Class 9 Science Chapter 7 Diversity in Living Organisms

The Living world includes an incredible number of diverse fascinating organisms. Living beings are found wherever life is possible. They are found in cold mountains, forests, oceans, lakes, deserts and hot water springs. There are so many varieties of living organisms that it would be almost impossible to study them all in a lifetime.

The branch of science that deals with the identification, naming and classification of organisms are called systematics or taxonomy.

It is not possible to study every organism existing on this earth. If we can arrange the organisms into groups and study one of the organisms from each group, it gives sufficient information about the essential features of that particular group. But without any system of classification, organisms cannot be studied Further, extinct organisms cannot be studied without the help of a well-established system of classification. Thus, the classification enables us to know the relationship among different groups of organisms. Based on this relationship existing among various groups, an evolutionary tendency can be established.

• How do we study such vast diversity?
• What is the need of being systematic to study diversity?
• Biodiversity: A general idea

Every organism of this living world, whether an animal, a point or a microorganism is unique in itself. The uniqueness is the basis of the diversity (or species richness) in life forms, which is the most important aspect of the biological world.

Diversity simply means a variety of forms. Thus, Biodiversity means different forms of living organisms or a variety of life forms found in a particular region.

For example, compare yourself with your friend. Both of you have different looks, different heights and different qualities. Now, compare ourselves and our friends with a monkey. The monkey is quite different from us because we and our friends have close similarities. The distinction becomes sharper if we compare ourselves with a monkey and a cow.

• NCERT Solutions for Class 9 Science Chapter 10 Gravitation

When a body is held in hand and then released, the body falls vertically downwards. Let us think as to why the body falls towards the earth? Why is it not going up? It was Sir Issac Newton who posed this question and he answered it.

It is said that when Newton was sitting under a tree, an apple fell on him. The fall of the apple made Newton think. He thought that if the earth can attract an apple can it not attract the moon? Is the force the same in both cases? He conjectured that the same type of force is responsible in both cases.

Newton was sitting under an apple tree when an apple fell on him. He thought that the apple fell due to the downward pull of the Earth on the apple.

When a body is thrown up, it reaches a certain height and then falls. The downward pull of the Earth, on the body, decreases its velocity in the upward direction to zero at some height. The body cannot rise further. This is, therefore, the maximum height attained by that body. The same downward pull of the Earth on the body makes it fall downwards from the maximum height.

Consider a piece of stone tied to one end of a string. Hold the other end of the string in hand and whirl it around. The stone moves in a circular path at a certain speed, but its direction of motion changes continuously. The change in direction of motion involves a change in velocity or acceleration of the stone. The external force F that causes this acceleration and keeps the stone moving uniformly along the circular path is acting towards the centre of the circular path.

This is called centripetal force, i.e., centre-seeking force. At any instant, if we release the string, the stone flies along the tangent to the circular path at that instant. This is because, the moment the string is released, centripetal force is no longer provided. The stone is free to fly off along the tangent. Based on this activity, we can perceive that the motion of the Moon around the Earth is due to centripetal force, provided by the force of attraction of the Earth on the Moon.

Gravitation is the phenomenon of attraction between any two objects in the universe. The objects may be terrestrial (which are on the Earth) or celestial (which are in outer space such as stars, planets, satellites etc.). Further, the objects may be of any size, shape or mass and they may be any distance apart (small or large), with any medium between them. The force gravitation is always the force of attraction and it is never repulsive.

• NCERT Solutions for Class 9 Science Chapter 11 Work, Power And Energy

1. Definition: Work is said to be done by a force on a body when the force displaces the body through, a certain distance in the direction of the force.
2. Measurement of Work:

The amount of work done by a body depends upon.

1. the magnitude of the force and
2. the displacement of the body.

So, by knowing the force and displacement, we can measure the work done. The amount of work done is equal to the product of the force and the displacement of the body from the point of application of the force, in the direction of the force.

Formula :

Work = Force × displacement of the body

• Nature of quantity: Even though force and displacement are vectors, work is a scalar quantity.
• Work is a scalar quantity. Work is independent of time.
• Units of work:

The work has the following units:

• Absolute units: SI units: joule (J)
• CGS unit: erg
• Joule: The work done is said to be 1 joule. If 1 N of the force displaces the body through 1m in the direction of the force
• Erg: The work done is said to be 1 erg, if 1 dyne of the force displaces the body through 1cm in the direction of the force. Other than these units, work also has units called ‘gravitational units’.
• Gravitational units: SI unit: kg-wt-m
• CGS unit: g-wt-cm

• NCERT Solutions for Class 9 Science Chapter 12 Sound

A wave is a vibratory disturbance in a medium which carries energy from one point to another, without there being a direct contact between the two points.

1. Type of waves based on the material medium

• Elastic waves or mechanical waves: Those waves which need a material medium for their propagation are called elastic waves or mechanical waves e.g., sound waves and water waves are elastic or mechanical waves
• Electromagnetic waves: Those waves which do not need a material medium for their propagation are called electromagnetic waves. These waves can travel through a vacuum as well as through medium e.g. light waves and radio waves are electromagnetic waves.
• Seismic waves: The disturbances inside the earth which cause waves moving in all directions are called seismic waves. It is these waves which cause earthquakes.

2. Types of waves based on their direction of propagation

• Transverse waves: The waves in which the particles of the medium vibrate up and down ‘at right angles’ to the direction in which the wave is moving, are called transverse waves. Eg., light waves, radio waves, water waves etc.

The water waves (or ripples) formed on the surface of the water in a pond are transverse waves. This is because, in a water wave, the molecules of water move up and down in the vertical direction when the wave travels in the horizontal direction along the water surface. When a stone is dropped in a pond of water, transverse water waves are produced on the surface of the water.

• NCERT Solutions for Class 9 Science Chapter 13 Why Do We Fall Ill

Health is a state of physical, mental, and social well-being. Physical health includes anything concerned with our bodies. It ensures the performance of many activities such as walking, running and exercising. Mental health includes the ability to express emotions appropriately, learn, take the right decisions etc. Social wellness includes social networks, level of interdependence, care, safety, acceptance of diversity, etc. Health is not just a disease-free condition.

Health is very precious. Nutrition, habits, exercise and relaxation are essential factors for good health. A person may be regarded as suffering from the disease when his body does not function properly. Minor and major disorders of the body may lead to diseases. Infectious diseases are caused by germs One way is to use medicines that kill germs (Pathogens). Many vaccines are now available for preventing a whole range of infectious diseases and provide a disease-specific means of prevention.

• People living in which of these two places do you think are more prone to diseases?
• Do you know that dogs can also cause a deadly disease, rabies?

Health and diseases in human communities are very complex issues with many interconnected causes.

All living organisms are made up of cells. The cell is the basic unit of life and is made up of a variety of inorganic [e.g. water, minerals, gases, salts etc.] and organic chemical substances [e.g. Proteins, lipids, carbohydrates etc.]. Cells regularly receive materials from extracellular fluid/outside environment and also regularly discharge certain material, extracellular. All these activities involve different tissues, organs and systems. This means that in the tissues or organs, many specialized activities are taking place which is interconnected. For example, if kidneys do not form urine properly, poisonous substances (e.g., urea) will start accumulating in the body. Under such circumstances, functions of the brain, heart and lungs will get affected.

For their functioning, cells require energy and raw materials. The same is obtained from food. Proper food is, therefore, a basic necessity for the proper functioning of cells, their tissues and organs. Anything that disturbs the proper functioning of cells, tissues and organs will result in the improper activity of the body. It may be poor or imbalanced food, injury, infirmity, or mental or social problems. A person can say to be healthy if one shows:

1. Absence of any infection.
2. Absence of physical deformity.
3. Absence of any hereditary defect.
4. Absence of sufficient diet.
5. Complete physical fitness
6. Absence of mental problems
7. Freedom from anxiety.
8. Freedom from psychological tensions.
9. Congenial surroundings.
10. Absence of social tensions.
11. Purposeful living.

• NCERT Solutions for Class 9 Science Chapter 15 Improvement in Food Resources

Food is any substance or material eaten to provide nutritional support to the body. Humans obtain food from both plants and animals that contain essential nutrients such as carbohydrates, fats, proteins, vitamins, and minerals and are ingested and assimilated to produce energy, stimulate growth and maintain life. Food-yielding plants and animals are reared by human beings under their supervision.

Agriculture helps to meet the basic needs of humans and their civilization by providing food, clothing, shelter and medicine. Hence, it is the most important enterprise in the world.

In India, population pressure is increasing while the area under cultivation is static or even shrinking, which demands intensification of cropping. India is endowed with a tropical climate with abundant solar energy throughout the year, which favours growing crops around the year.

There is a vast scope to increase irrigation potential through river projects and minor irrigation projects. In addition to this, India is blessed with more labour availability. Because agriculture is the primary sector, other sectors are dependent on agriculture.

• Why do sunflower plots tend to have few weeds?
• Can living plants also act as manure?

INTRODUCTION

All living organisms require food, though the type of food needed by different organisms may vary.

Food is the combination of various organic substances which is capable of providing

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1. Energy for the various metabolic activities.
2. Materials for repair/replacement of worn-out tissues in the body.
3. Materials for growth & reproduction.
4. Regulatory substances, body secretions and metabolic activities etc.