Revision Term 1 Ncert Science Grade 10

# Revision Term 1: NCERT Science Grade 10

Welcome to your comprehensive revision guide for the NCERT Class 10 Science Term 1 examination. This course is meticulously designed to provide you with a thorough understanding of the fundamental concepts and principles that form the bedrock of your scientific knowledge. Our goal is to empower you with the expertise, authoritativeness, and trustworthiness (E-E-A-T) you need to excel in your exams and beyond. We will delve into the fascinating worlds of chemistry, biology, and physics, exploring the intricate mechanisms that govern our universe.

This guide is structured to align with the CBSE Term 1 syllabus, ensuring that you cover all the essential topics in a systematic and organized manner. We will supplement our explanations with engaging YouTube videos from reputable educational channels to provide you with a dynamic and interactive learning experience. Furthermore, we will cite authoritative sources to ensure the accuracy and credibility of the information presented.

## Unit 1: Chemical Substances – Nature and Behaviour

### Chapter 1: Chemical Reactions and Equations

Chemical reactions are the processes in which new substances with new properties are formed. In this chapter, we will explore the different types of chemical reactions, how to write and balance chemical equations, and the various factors that influence the rate of a reaction. Understanding these concepts is crucial for comprehending the chemical changes that occur around us every day.

#### Balancing Chemical Equations

A balanced chemical equation has an equal number of atoms of each element on both sides of the equation. This is in accordance with the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. [1]

#### Types of Chemical Reactions

There are several types of chemical reactions, each with its unique characteristics. The main types of reactions are:

* **Combination Reaction:** Two or more reactants combine to form a single product.
* **Decomposition Reaction:** A single reactant breaks down into two or more simpler products.
* **Displacement Reaction:** A more reactive element displaces a less reactive element from its compound.
* **Double Displacement Reaction:** Two compounds react by an exchange of ions to form two new compounds.
* **Redox Reaction:** A reaction in which both oxidation and reduction take place simultaneously.

> “A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another.” [2]

We will now explore each of these reaction types in detail, with examples and explanations to solidify your understanding.

#### Combination Reactions

In a combination reaction, two or more reactants combine to form a single product. A classic example is the formation of water from hydrogen and oxygen:

2H₂ + O₂ → 2H₂O

Another example is the burning of magnesium in air to form magnesium oxide:

2Mg + O₂ → 2MgO

Combination reactions are often exothermic, meaning they release energy in the form of heat and light. This is why the burning of magnesium produces a bright white flame.

#### Decomposition Reactions

Decomposition reactions are the opposite of combination reactions. In these reactions, a single reactant breaks down into two or more simpler products. For example, when calcium carbonate is heated, it decomposes into calcium oxide and carbon dioxide:

CaCO₃ → CaO + CO₂

Another example is the electrolysis of water, where an electric current is used to decompose water into hydrogen and oxygen:

2H₂O → 2H₂ + O₂

Decomposition reactions often require energy input in the form of heat, light, or electricity.

#### Displacement Reactions

In a displacement reaction, a more reactive element displaces a less reactive element from its compound. For example, when zinc is added to copper sulfate solution, zinc displaces copper:

Zn + CuSO₄ → ZnSO₄ + Cu

The reactivity series of metals helps us predict which metals will displace others from their compounds. Metals higher in the reactivity series can displace metals lower in the series.

#### Double Displacement Reactions

In double displacement reactions, two compounds react by an exchange of ions to form two new compounds. For example, when silver nitrate solution is mixed with sodium chloride solution, silver chloride precipitates out:

AgNO₃ + NaCl → AgCl + NaNO₃

These reactions often result in the formation of a precipitate, a gas, or water.

#### Redox Reactions

Redox reactions involve both oxidation (loss of electrons) and reduction (gain of electrons). For example, when magnesium reacts with oxygen, magnesium is oxidized (loses electrons) and oxygen is reduced (gains electrons):

2Mg + O₂ → 2MgO

Understanding redox reactions is crucial in many fields, including electrochemistry and corrosion science.

### Chapter 2: Acids, Bases and Salts

Acids, bases, and salts are three important classes of chemical compounds that we encounter in our daily lives. From the citric acid in lemons to the sodium bicarbonate in baking soda, these compounds play a vital role in various biological and industrial processes. In this chapter, we will delve into the properties of acids and bases, their reactions, and the formation of salts. [3]

#### Properties of Acids and Bases

Acids are substances that produce hydrogen ions (H+) in an aqueous solution, while bases are substances that produce hydroxide ions (OH-) in an aqueous solution. The table below summarizes their key properties:

| Property | Acids | Bases |
| :— | :— | :— |
| Taste | Sour | Bitter |
| Litmus Test | Turn blue litmus red | Turn red litmus blue |
| pH | Less than 7 | Greater than 7 |
| Reaction with Metals | Produce hydrogen gas | Generally do not react with metals |

#### pH and its Importance

The pH scale is a measure of the acidity or alkalinity of a solution. It ranges from 0 to 14, with 7 being neutral. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic or alkaline solution. The pH of a solution is a critical factor in many chemical and biological processes. For example, our bodies need to maintain a specific pH range for enzymes to function correctly. [4]

#### Reactions of Acids and Bases

Acids and bases undergo various chemical reactions that are important in both laboratory and industrial settings. Some key reactions include:

**Reaction with Metals:** Acids react with metals to produce hydrogen gas and a salt. For example:

Zn + 2HCl → ZnCl₂ + H₂

**Reaction with Metal Carbonates:** Acids react with metal carbonates to produce carbon dioxide gas, water, and a salt:

Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

**Neutralization Reaction:** When an acid reacts with a base, they neutralize each other to form salt and water:

HCl + NaOH → NaCl + H₂O

This reaction is the basis for many applications, including the treatment of acid indigestion and the neutralization of acidic soils.

#### Indicators

Indicators are substances that change color depending on the pH of the solution. Common indicators include litmus, phenolphthalein, and methyl orange. These indicators help us determine whether a solution is acidic or basic.

### Chapter 3: Metals and Non-metals

Metals and non-metals are two major classes of elements that exhibit distinct physical and chemical properties. This chapter will explore these properties, their reactions, and their applications in various fields. Understanding the differences between metals and non-metals is fundamental to comprehending the periodic table and the behavior of elements.

#### Physical Properties of Metals and Non-metals

| Property | Metals | Non-metals |
| :— | :— | :— |
| State | Generally solid at room temperature (except mercury) | Can be solid, liquid, or gas at room temperature |
| Luster | Have a shiny appearance | Have a dull appearance |
| Malleability | Can be beaten into thin sheets | Are brittle and cannot be beaten into sheets |
| Ductility | Can be drawn into wires | Are not ductile |
| Conductivity | Good conductors of heat and electricity | Poor conductors of heat and electricity (except graphite) |

#### Chemical Properties of Metals and Non-metals

Metals and non-metals also differ significantly in their chemical properties. For instance, metals tend to lose electrons to form positive ions (cations), while non-metals tend to gain electrons to form negative ions (anions). These differences in reactivity are crucial in determining how they interact with other elements and compounds. [5]

**Reaction with Oxygen:** Metals react with oxygen to form metal oxides, which are generally basic in nature:

4Al + 3O₂ → 2Al₂O₃

Non-metals react with oxygen to form non-metal oxides, which are generally acidic in nature:

C + O₂ → CO₂

**Reaction with Water:** Some metals react with water to form metal hydroxides and hydrogen gas:

2Na + 2H₂O → 2NaOH + H₂

**Reaction with Acids:** Metals react with acids to produce hydrogen gas and a salt:

Mg + 2HCl → MgCl₂ + H₂

#### Reactivity Series

The reactivity series is a list of metals arranged in order of their decreasing reactivity. Metals at the top of the series are more reactive than those at the bottom. This series is useful in predicting the outcome of displacement reactions and the extraction of metals from their ores.

#### Extraction of Metals

Metals are extracted from their ores through various processes, depending on their reactivity. Highly reactive metals like sodium and potassium are extracted by electrolysis, while less reactive metals like iron and zinc are extracted by reduction with carbon. The extraction of metals is a crucial industrial process that provides us with the materials we need for construction, manufacturing, and technology.

## Unit 2: World of Living

### Chapter 6: Life Processes

Life processes are the essential functions that living organisms perform to maintain and perpetuate life. In this chapter, we will explore the fundamental life processes, including nutrition, respiration, transportation, and excretion. A comprehensive understanding of these processes is key to appreciating the complexity and beauty of living organisms.

#### Nutrition

Nutrition is the process by which an organism obtains and utilizes food. There are two main modes of nutrition: autotrophic nutrition, where organisms produce their own food (e.g., plants through photosynthesis), and heterotrophic nutrition, where organisms obtain food from other organisms. [6]

#### Respiration

Respiration is the process of releasing energy from food. It can be aerobic (in the presence of oxygen) or anaerobic (in the absence of oxygen). Aerobic respiration is more efficient and releases more energy than anaerobic respiration.

#### Transportation

Transportation is the process of moving substances from one part of the body to another. In plants, water and minerals are transported through the xylem, while food is transported through the phloem. In animals, the circulatory system, consisting of the heart, blood, and blood vessels, is responsible for transportation.

#### Excretion

Excretion is the process of removing waste products from the body. In humans, the excretory system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter waste products from the blood to form urine.

**Excretion in Plants:** Plants also excrete waste products, but they do so in different ways. Some waste products are stored in leaves that eventually fall off, while others are stored in the bark or excreted as gums and resins.

#### Photosynthesis

Photosynthesis is the process by which green plants use sunlight to synthesize food from carbon dioxide and water. This process is essential for life on Earth, as it produces oxygen and provides the energy that sustains most ecosystems. The overall equation for photosynthesis is:

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

Photosynthesis occurs in the chloroplasts of plant cells, which contain the green pigment chlorophyll. Chlorophyll absorbs light energy, which is then used to convert carbon dioxide and water into glucose and oxygen.

#### Control and Coordination

Living organisms need to respond to changes in their environment to survive. This requires a system for control and coordination. In animals, the nervous system and the endocrine system work together to coordinate various activities. The nervous system uses electrical signals to transmit information quickly, while the endocrine system uses hormones to regulate long-term processes.

**The Nervous System:** The nervous system consists of the brain, spinal cord, and nerves. It receives information from sensory organs, processes it, and sends signals to muscles and glands to produce a response.

**The Endocrine System:** The endocrine system consists of glands that secrete hormones directly into the bloodstream. These hormones regulate various functions, including growth, metabolism, and reproduction.

## Unit 3: Natural Phenomena

### Chapter 10: Light – Reflection and Refraction

Light is a form of energy that enables us to see the world around us. This chapter explores the fascinating phenomena of reflection and refraction of light. We will learn about the laws of reflection, the formation of images by mirrors and lenses, and the principles of refraction.

#### Reflection of Light

Reflection is the bouncing back of light when it strikes a surface. The two laws of reflection are:

1. The angle of incidence is equal to the angle of reflection.
2. The incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.

#### Refraction of Light

Refraction is the bending of light as it passes from one medium to another. This phenomenon is responsible for the apparent bending of a straw in a glass of water. The laws of refraction, also known as Snell’s law, describe the relationship between the angles of incidence and refraction and the refractive indices of the two media. [7]

**Snell’s Law:** The relationship between the angles of incidence and refraction is given by:

n₁ sin θ₁ = n₂ sin θ₂

where n₁ and n₂ are the refractive indices of the two media, and θ₁ and θ₂ are the angles of incidence and refraction, respectively.

#### Lenses and Image Formation

Lenses are transparent optical devices that refract light to form images. There are two main types of lenses: convex lenses and concave lenses.

**Convex Lenses:** Convex lenses are thicker in the middle than at the edges. They converge light rays to a focal point and are used in magnifying glasses, cameras, and eyeglasses to correct farsightedness.

**Concave Lenses:** Concave lenses are thinner in the middle than at the edges. They diverge light rays and are used in eyeglasses to correct nearsightedness.

The lens formula relates the object distance (u), image distance (v), and focal length (f) of a lens:

1/f = 1/v – 1/u

#### Mirrors and Image Formation

Mirrors are reflective surfaces that form images by reflecting light. There are two main types of mirrors: plane mirrors and spherical mirrors (concave and convex).

**Plane Mirrors:** Plane mirrors form virtual, erect images of the same size as the object.

**Spherical Mirrors:** Spherical mirrors can be concave (converging) or convex (diverging). The mirror formula for spherical mirrors is:

1/f = 1/v + 1/u

where f is the focal length, v is the image distance, and u is the object distance.

### Chapter 11: The Human Eye and the Colourful World

The human eye is a remarkable and complex organ that allows us to perceive the vibrant world around us. This chapter will explore the structure and functioning of the human eye, common vision defects and their correction, and the beautiful phenomenon of the dispersion of light.

#### The Human Eye

The human eye works on the principle of refraction of light. It consists of several parts, including the cornea, iris, pupil, lens, and retina. The lens focuses light onto the retina, which contains light-sensitive cells that send signals to the brain, allowing us to see.

#### Defects of Vision

Common defects of vision include:

* **Myopia (Nearsightedness):** The inability to see distant objects clearly. It is corrected using a concave lens.
* **Hypermetropia (Farsightedness):** The inability to see nearby objects clearly. It is corrected using a convex lens.
* **Presbyopia:** The gradual loss of the eye’s ability to focus on nearby objects, which occurs with age. It is corrected using bifocal lenses.

#### Dispersion of Light

Dispersion is the splitting of white light into its constituent colors when it passes through a prism. This phenomenon is responsible for the formation of a rainbow. The band of seven colors obtained is called a spectrum.

The seven colors of the spectrum, in order of increasing wavelength, are: violet, indigo, blue, green, yellow, orange, and red (VIBGYOR). Each color has a different wavelength and frequency, which is why they are refracted at different angles when passing through a prism.

#### Atmospheric Refraction and Scattering

Atmospheric refraction is the bending of light as it passes through the Earth’s atmosphere. This phenomenon is responsible for several optical effects, including the twinkling of stars and the apparent flattening of the Sun at sunrise and sunset.

Scattering of light is the phenomenon in which light is deflected in various directions by particles in the atmosphere. The scattering of sunlight by air molecules is responsible for the blue color of the sky. Shorter wavelengths (blue and violet) are scattered more than longer wavelengths (red and orange), which is why the sky appears blue during the day and red or orange during sunrise and sunset.

## Conclusion

This comprehensive revision guide has covered the essential topics from the NCERT Class 10 Science Term 1 syllabus. We have explored the fascinating worlds of chemistry, biology, and physics, delving into the fundamental concepts and principles that govern our universe. From understanding chemical reactions and equations to exploring the properties of acids, bases, and salts, from examining the characteristics of metals and non-metals to investigating the life processes that sustain living organisms, and from studying the reflection and refraction of light to understanding the structure and functioning of the human eye, this guide has provided you with a solid foundation for your Term 1 examination.

As you prepare for your exams, remember that consistent practice and revision are key to success. Work through the practice problems in your NCERT textbook, review the key concepts and formulas, and watch the embedded YouTube videos to reinforce your understanding. With dedication and hard work, you will be well-prepared to excel in your Class 10 Science Term 1 examination.

We encourage you to use this guide as a reference throughout your studies and to revisit the concepts as needed. Science is a subject that builds upon itself, so a strong understanding of these fundamental topics will serve you well in your future studies. Good luck with your exams, and may your scientific journey be filled with discovery and wonder!

## References

[1] NCERT. (n.d.). *Science – Class X*. National Council of Educational Research and Training. Retrieved from https://ncert.nic.in/textbook.php?jesc1=0-16

[2] BYJU’S. (n.d.). *Chemical Reactions and Equations Class 10 Notes*. Retrieved from https://byjus.com/cbse-notes/class-10-science-notes-chapter-1-chemical-reactions-and-equations/

[3] Vedantu. (n.d.). *CBSE Class 10 Science Revision Notes*. Retrieved from https://www.vedantu.com/revision-notes/cbse-class-10-science-notes

[4] Khan Academy. (n.d.). *Acids, bases, and pH*. Retrieved from https://www.khanacademy.org/science/chemistry/acids-and-bases-topic/acids-and-bases/a/acids-bases-and-ph

[5] Toppr. (n.d.). *Metals and Non-metals*. Retrieved from https://www.toppr.com/guides/science/metals-and-non-metals/

[6] BYJU’S. (n.d.). *Life Processes Class 10 Notes*. Retrieved from https://byjus.com/cbse-notes/class-10-science-notes-chapter-6-life-processes/

[7] Physics Classroom. (n.d.). *Refraction of Light*. Retrieved from https://www.physicsclassroom.com/class/refrn/Lesson-1/Refraction