CBSE Class 9 Science Revision Notes Chapter 1

CBSE Class 9 Science Revision Notes Chapter 1 – Matter in Our Surroundings 

All objects with mass and space are considered to be matter. For example, water, air, oxygen, fruits, etc. All these are classified as solids, liquids and gases and are considered to be matter in our surroundings. They are made up of molecules that are microscopic particles (which are tightly, loosely and very loosely packed, respectively). 

Class 9 Science Chapter 1 Notes – Notes on the chapter Matter in Our Surroundings provided by Extramarks can be of immense help to students during their revisions. Along with the textbooks, referring to these notes for a detailed understanding of the topics will also help them better perform in exams. 

To access Class 9 Chapter 1 Science Notes provided by Extramarks, all one has to do is create an account and log in on the website. The students can then focus on studying these notes before their exams to get a comprehensive overview of the whole chapter.

Matter in our Surroundings Notes Free Download 

Everything around us is made up of matter: from a pencil, a pen and a table, to the food we consume, the clothes we wear and even the walls of our homes. But what exactly is matter? Anything that occupies space and has mass, and can be sensed by our senses, is considered to be matter. In other words, the term “matter” refers to all the materials and substances that make up the cosmos. 

Chapter 1 Science Class 9 Notes by Extramarks can be easily availed from Extramarks’ website. Students can access them and make a revision guide for both unit tests and examinations. By doing so, they will no longer need to prepare a list of important topics and explanations by themselves. Besides, the usage of simple and easy-to-understand language makes it a perfect revision guide. It is curated by subject matter experts as per the latest CBSE Syllabus.

Class 9 Chapter 1 Science Notes – Summary 

The notes of Chapter 1 Science of Class 9 start with an introduction to the matter in our surroundings, what it is made up of, i.e. its composition, etc. Though this is covered in earlier classes, students must study it again to have a proper understanding of this concept. 

The next part of Class 9 Science Notes Chapter 1 explains the properties of matter. Matter is made up of tiny particles that possess unique characteristics. Additionally, these characteristics of matter are provided by a theory known as the Kinetic Theory of Matter which states the following key points:

• There is space between particles of matter.
• Particles of matter are continuously in motion–rotational and vibrational motion.
• Particles of matter generally attract each other.

Diffusion 

In the next section of Science Class 9 Chapter 1 Notes, students will get to learn about diffusion; the provided diagram will make it easy to understand. They also learn that diffusion occurs at a faster rate in gases. The reason for this is elaborated upon with suitable examples in the notes. Diffusion in liquids and solids is also discussed in detail, which will help students comprehend this concept clearly.

When the mixing and spreading out of a substance with another substance takes place, due to the movement or motion of its particles, it is called diffusion.

The diffusion process of a substance with another continues until a homogenous mixture is achieved. An illustration of this is:

Put a crystal of potassium permanganate which is purple in colour in a beaker full of water. Gradually, you will notice that the purple-coloured crystal begins to dissolve or diffuse into the water, and after a while, the water will turn purple.

States of Matter 

A detailed explanation of the three states of matter– solid, liquid and gas – is accurately laid out in this Class 9 Matter in our Surroundings Notes alongside their various properties. Also, a tabular representation of differences between the three states of matter is given.

Interconversion of the States of Matter 

Matter can change from one form to another with a change in temperature and pressure. This section of Class 9 Science Chapter 1 Notes deals with this concept. After going through these notes, students will learn about the changes in states of matter, like solidification, vaporisation, melting, condensation, sublimation, etc. 

Therefore, changing the pressure, temperature, or both can cause matter to change its physical condition.

1. Melting – Conversion of solid into liquid
2. Solidification – Conversion of liquid into solid
3. Vaporisation – Conversion of liquid into gas
4. Condensation – Conversion of gas into liquid
5. Sublimation – Conversion of solid into gas

Note: While pressure is increased in a gas, it will cause the gas to liquefy to bring the particles closer together and not change the physical conditions of the gas. Vaporisation is promoted by decreasing pressure over the surface of a liquid. 

Latent Heat and Latent Heat of Vaporisation and Fusion 

This section deals with latent heat and its different types – latent heat of fusion and latent heat of vaporisation. The values of latent heat of different things are also given. Students can go through the Matter in our Surroundings Class 9 Notes to increase their understanding of the chapter.

The amount of heat that any substance needs to change its condition without increasing its temperature is known as latent heat (hidden heat). It is called so as it is buried in the substance undergoing a state transition and doesn’t show up as a rise in temperature. “The latent heat is utilised in overcoming the force of attraction between the particles of the substance during a transition of state. It does not affect the kinetic energy of the particles of substances since the substance’s temperature does not rise.”

The amount of heat in Joules needed to turn a unit quantity of 1 kg liquid into vapours without a temperature change is known as latent heat of vaporisation. Experiments have made it clear that it takes 22.5 × 105 joules of heat to convert 1 kilogramme of water at its boiling point, 100°C (to steam at the same temperature). Hence, as a result, the latent heat of the vaporisation of water is 22.5 × 105 joules per kilogramme (or 22.5 × 105 J/kg). 

The latent heat of vaporisation depends on the substance, and therefore, it varies. 

As a general rule, “if the liquid freezes to form a solid and steam condenses to convert into the water, the substance will emit an equal amount of latent heat of vaporisation and fusion.” 

Sublimation, Evaporation and Cooling Effect 

In the last section of Chapter 1 Class 9 Notes of Science, students will learn about evaporation, sublimation and cooling effects. All these processes of changes in state are explained thoroughly in the notes with appropriate examples. Here’s a quick brief of these processes: 

1. Sublimation is the process of transformation of a solid into vapours on heating and then back into a solid on cooling. 

Solid ⇄ Vapour (or Gas)  

Common chemicals that sublimate are iodine, anthracene, ammonium chloride, camphor, and naphthalene. Solid carbon dioxide, sometimes known as dry ice, is yet another instance of sublimation. Carbon dioxide gas is created when solid carbon dioxide (dry ice) sublimates.

2. When a liquid turns into a gaseous form below its boiling point, evaporation takes place.

Water molecules are drawn to one another in all directions, but those close to the water’s surface are only pulled inward or below the water’s surface.

Note: Evaporation is a process that occurs in all liquids in theory. In general, evaporation mostly refers to water evaporation.

Vapour is a substance that remains in a gaseous state at a temperature where it would ordinarily be a liquid or solid. Examples of solids that can exist in vapour form are naphthalene and camphor.

3. Cooling effect caused by evaporation- Energy is generally extracted from a liquid when it evaporates and, as a result, it continues to cool. As the liquid absorbs the energy lost by the surroundings, it causes the liquid to cool. For instance, during summer, air coolers are utilised to provide forced cooling.