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Ask QuestionPosted by Ashna Gurjar 3 years, 9 months ago
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Posted by Deepali Patel 3 years, 9 months ago
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Neshok Neshok 3 years, 9 months ago
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Somansh Sarvesh 3 years, 8 months ago
Divyanshi Sharma 3 years, 9 months ago
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Gaurav Seth 3 years, 9 months ago
CBSE Class 9 Science (086) - Deleted portion (Theory):
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Unit I: Matter-Nature and Behaviour |
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Chapter |
Topics |
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Matter in Our Surroundings |
Definition of matter; solid, liquid and gas; characteristics - shape, volume, density; change of state-melting (absorption of heat), freezing, evaporation (cooling by evaporation), condensation, sublimation. |
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Unit II: Organization in the Living World |
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Chapter |
Topics |
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Diversity in Living Organisms |
Diversity of plants and animals-basic issues in scientific naming, basis of classification. Hierarchy of categories / groups, Major groups of plants (salient features) (Bacteria, Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms). Major groups of animals (salient features) (Non-chordates upto phyla and chordates upto classes). |
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Unit III: Motion, Force and Work |
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Chapter |
Topics |
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Floatation |
Thrust and Pressure. Archimedes’ Principle; Buoyancy; Elementary idea of Relative Density. |
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Sound |
Nature of sound and its propagation in various media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo and SONAR. Structure of the Human Ear (Auditory aspect only). |
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Unit V: Food Production |
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Chapter |
Topics |
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Improvement in Food Resources |
Plant and animal breeding and selection for quality improvement and management; Use of fertilizers and manures; Protection from pests and diseases; Organic farming. |
Posted by Deep Gopal 3 years, 9 months ago
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Posted by Manoj Agarwal 3 years, 9 months ago
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Posted by Bikash Boro 3 years, 9 months ago
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Yogita Ingle 3 years, 9 months ago
- Biodiversity describes the richness and variety of life on earth. It is the most complex and important feature of our planet. Without biodiversity, life would not sustain.
- The term biodiversity was coined in 1985. It is important in natural as well as artificial ecosystems. It deals with nature’s variety, the biosphere. It refers to variabilities among plants, animals and microorganism species.
- Biodiversity includes the number of different organisms and their relative frequencies in an ecosystem. It also reflects the organization of organisms at different levels.
- Biodiversity holds ecological and economic significance. It provides us with nourishment, housing, fuel, clothing and several other resources. It also extracts monetary benefits through tourism. Therefore, it is very important to have a good knowledge of biodiversity for a sustainable livelihood.
Gaurav Seth 3 years, 9 months ago
The variety of animals and plants living in a given geographical area is called biodiversity of that geographical area.
“Biodiversity is the variation among living organisms from different sources including terrestrial, marine and desert ecosystems, and the ecological complexes of which they are a part.
Posted by Prince Raj 3 years, 9 months ago
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Hasina Mandar 3 years, 9 months ago
Gaurav Seth 3 years, 9 months ago
Homogeneous Mixture
Mixtures which have uniform composition throughout are called Homogeneous Mixture. For example – mixture of salt and water, mixture of sugar and water, air, lemonade, soda water, etc.
Mixture of salt in water is an example of homogeneous mixture. In this mixture, the boundary of salt and water cannot be differentiated. When a ray of light is passed through the mixture of salt and water, the path of light is not seen.
Nitya Ranout 3 years, 9 months ago
Posted by Jigyasha Karam Chandani 3 years, 9 months ago
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Gaurav Seth 3 years, 9 months ago
Some noise pollution preventive measures are provided in the points below.
- Honking in public places like teaching institutes, hospital, etc. should be banned.
- In commercial, hospital, and industrial buildings, adequate soundproof systems should be installed.
- Musical instruments sound should be controlled to desirable limits.
Prevention of water pollution
It is important to dispose-off waste carefully and not to dump them directly into water bodies, without proper waste treatment. Using natural fertilisers and pesticides as substitutes for chemical ones are good for plants and water. Industries should treat their wastes carefully before disposing of chemicals and other materials into water bodies directly.
Posted by Tiger Goswami 3 years, 9 months ago
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Yogita Ingle 3 years, 9 months ago
Oxygen is called diatomic oxygen and ozone is known as triatomic oxygen.
Posted by Prajwal G N 3 years, 9 months ago
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Tejal Kaur 3 years, 9 months ago
Sameer Singh 3 years, 9 months ago
Neshok Ls 3 years, 9 months ago
Gaurav Seth 3 years, 9 months ago
Cell is the smallest and fundamental unit of life. It is the basic unit which made all the living organisms.
Types of cell...
1.Unicellular cells made of only one types of cell.
eg amoeba., plasmodium, etc
2..Muticellular cells made of many types of cells.
eg human beings, other animals.
Posted by P A 3 years, 9 months ago
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Yogita Ingle 3 years, 9 months ago
Molar mass of Na=23g/mol
no. of moles = weight/molar mass
n = 11.5/23
no. of moles = 0.5
no. of moles = no. of atoms/avogadro’s number
0.5 = no. of atoms/6.022*10^23
0.5*6.022*10^23 atoms = no. of atoms
3.011*10^23 atoms.
So there are 3.011*10^23 atoms present in 11.5g of sodium sample.
Gaurav Seth 3 years, 9 months ago
Explanation:
Molar mass of Na=23g/mol
no. of moles = weight/molar mass
n = 11.5/23
no. of moles = 0.5
no. of moles = no. of atoms/avogadro’s number
0.5 = no. of atoms/6.022*10^23
0.5*6.022*10^23 atoms = no. of atoms
3.011*10^23 atoms.
So there are 3.011*10^23 atoms present in 11.5g of sodium sample
Posted by R Mahendhiran 3 years, 9 months ago
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Yogita Ingle 3 years, 9 months ago
The bone matrix contains hydroxyapatite, which consists of mainly calcium and phosphorus with trace amounts of sodium, magnesium, and bicarbonate.
Neshok Ls 3 years, 9 months ago
Posted by Chetan Thakre 3 years, 9 months ago
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Gaurav Seth 3 years, 9 months ago
If velocity is doubled, Kinetic Energy increases by 4 times.
Kinetic energy of a body is the energy possessed by it, by virtue of its motion, i.e. if the body is moving it will always have kinetic energy.
so kinetic energy is directly proportional to v^2
coz mass is constant
so new kinetic energy changes as (2v)^2 =4v^2
so kinetic energy increases 4 times
Posted by Gouri Sharma 3 years, 9 months ago
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Gaurav Seth 3 years, 9 months ago
ANSWER
Division of labour is differentiation of certain components or parts to perform different functions for increased efficiency and higher survival. Multicellular organisms often possess millions of cells. All the cells are not similar. The cell present on the surface is dead and impermeable to protect the internal cells from the harsh external environment. They also form structures for offence and defence of the organism.
Every cell of a multicellular organism cannot obtain food from outside. The organism requires a system for obtaining requires a system for obtaining food. Its digestion and distribution. Therefore, a digestive system and system of transport are also required.
Certain cells of the body take over the function of reproduction. Others take part in repair and replacement of worn out or injured portions.
For optimum functioning of cells, a multicellular organism also comes to have an internal favourable environment.
Posted by Girish Naik 3 years, 9 months ago
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Yogita Ingle 3 years, 9 months ago
A cell is the structural and fundamental unit of life. The study of cells from its basic structure to the functions of every cell organelle is called Cell Biology. Robert Hooke was the first Biologist who discovered cells.
All organisms are made up of cells. They may be made up of a single cell (unicellular), or many cells (multicellular). Mycoplasmas are the smallest known cells. Cells are the building blocks of all living beings. They provide structure to the body and convert the nutrients taken from the food into energy.
Cells are complex and their components perform various functions in an organism. They are of different shapes and sizes, pretty much like bricks of the buildings. Our body is made up of cells of different shapes and sizes.
Posted by Hardik Pandey 3 years, 9 months ago
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Saurabh Gupta 3 years, 9 months ago
Gaurav Seth 3 years, 9 months ago
Atomicity is the total number of atoms present in one molecule of an element or a substance.
Here, atomicity of He is one. As helium is a noble gas, it do not combine and also exists as a monoatomic gas.
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Posted by Aditya Rana 3 years, 9 months ago
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Gaurav Seth 3 years, 9 months ago
WBC – White Blood Cells
Other details:
| White Blood Cells are called Leucocytes or Leukocytes. |
| WBCs have an irregular shape. |
| Size varies from 12 – 17 µm in diameter. |
| The lifespan of WBC is around 12-20 days after which, they are destroyed in the lymphatic system |
| WBCs are characterized by the presence of a large central nucleus. |
| These cells are colourless, as they do not have any pigment. |
| Different types of WBCs are found in the blood such as neutrophils, B lymphocytes, T lymphocytes, monocytes, basophils, eosinophils. |
Posted by Anmol Tomar 3 years, 9 months ago
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Saurabh Gupta 3 years, 9 months ago
Gaurav Seth 3 years, 9 months ago
After the discovery of electrons and protons,it was noticed that all mass of an atom cannot be accounted for on the basis of only protons and electrons.Then the neutrons were discovered.
Chadwick in 1932 discovered another subatomic particle called neutron.
Neutron is present inside the nucleus.
Hydrogen atom does not contain any nucleus.
Characteristics of neutron
1)The mass of neutron is equal to mass of proton.The relative mass of neutron is 1 u and absolute mass is 1.6749 x 10-27 kg.
2)Neutron has no charge.
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Yogita Ingle 3 years, 9 months ago
Connective tissues, as the name implies, support and connect different tissues and organs of the body. They are widely distributed in every part of the body. They originate from the mesoderm (the middle germinal layer of the embryo).
Connective tissues contain three types of fibres: collagen, elastic and reticular
Collagen fibres are the most widespread and made up of fibrous protein, collagen. Collagen fibres are flexible and have high tensile strength (comparable to steel).
Elastic fibres form a network and can be stretched like a rubber band. They are made up of protein elastin. They retain their original shape and size once the force is removed.
Reticulate fibres consist of collagen and glycoproteins. They are thin and form a delicate network. They join connective tissues to neighbouring tissues.
Posted by Chaudhary Shagun Mathur 3 years, 9 months ago
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Amit Sahu 3 years, 9 months ago
Gaurav Seth 3 years, 9 months ago
The smallest cell in the human body is the sperm cell.
These cells are small in volume. Head of the sperm cell measures about 4 micrometres in length, just a little bit smaller than a red blood cell (RBCs).
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Ashna Gurjar 3 years, 8 months ago
1Thank You