Class 9 Science Chapter 1: Matter in Our Surroundings
In this article, we will learn about the first chapter of Class 9 Science, which is about matter and its properties. We will understand what matter is, how it is classified, how it behaves in different states, and what factors affect its state. We will also look at some important questions and answers related to this chapter.
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Introduction
What is matter?
Matter is anything that has mass and occupies space. Everything that we can see, touch, smell, taste, or hear is made up of matter. For example, air, water, soil, plants, animals, rocks, metals, plastics, etc. are all examples of matter.
How is matter classified?
Matter can be classified in different ways based on its physical properties and chemical nature. One way to classify matter is based on its physical state: solid, liquid, or gas. Another way to classify matter is based on its composition: pure substance or mixture. A pure substance is a type of matter that has a fixed composition and cannot be separated into simpler substances by physical methods. For example, iron, copper, oxygen, water, etc. are pure substances. A mixture is a type of matter that contains two or more pure substances mixed together in any proportion and can be separated by physical methods. For example, air, sea water, milk, soil, etc. are mixtures.
Physical nature of matter
Characteristics of particles of matter
Matter is made up of very small particles that are too tiny to be seen with naked eyes. These particles have some characteristics that determine the physical nature and behaviour of matter. Some of these characteristics are:
Particles of matter have space between them: The particles of matter are not tightly packed but have some empty space between them. This space varies depending on the state and type of matter.
Particles of matter are constantly moving: The particles of matter are not stationary but have kinetic energy that makes them move randomly in all directions. This movement also varies depending on the state and temperature of matter.
Particles of matter attract each other: The particles of matter have some force of attraction between them that keeps them together. This force also varies depending on the state and distance between the particles.
All matter is composed of very small particles which can exist independently: The smallest unit of matter that can exist independently is called an atom. An atom is the building block of all matter and cannot be divided further by chemical methods. Atoms can combine with other atoms to form molecules, which are also particles of matter.
States of matter
Matter can exist in three main states: solid, liquid, and gas. These states differ in their shape, volume, density, compressibility, fluidity, movement, interparticle space, interparticle attraction, and rate of diffusion.
PropertySolidLiquidGas
Shape and volumeFixed shape and volumeNo fixed shape but has volumeNeither definite shape nor volume
EnergyLowestMediumHighest
CompressibilityDifficultNearly difficultEasy
Arrangement of moleculesRegular and closely arrangedRandom and little sparsely arrangedRandom and more sparsely arranged</td Change of state of matter
Matter can change its state from one to another by changing the temperature or pressure. The change of state of matter is a physical change, which means that the identity and composition of the substance remain the same. The change of state of matter involves two processes: fusion and vaporization.
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Fusion is the process of changing a solid into a liquid by heating it. For example, ice melts into water when heated. The temperature at which a solid changes into a liquid is called its melting point. Different solids have different melting points depending on the strength of their interparticle attraction.
Vaporization is the process of changing a liquid into a gas by heating it. For example, water boils into steam when heated. The temperature at which a liquid changes into a gas is called its boiling point. Different liquids have different boiling points depending on the strength of their interparticle attraction.
There are two types of vaporization: evaporation and boiling. Evaporation is the process of changing a liquid into a gas at any temperature below its boiling point. For example, water evaporates from the surface of oceans, lakes, and rivers. Boiling is the process of changing a liquid into a gas at its boiling point. For example, water boils in a kettle when heated.
Factors affecting the state of matter
Effect of temperature
Temperature is a measure of the average kinetic energy of the particles of matter. The higher the temperature, the faster the particles move and the more they collide with each other. This affects the state of matter in two ways:
Increasing the temperature increases the kinetic energy of the particles, which overcomes the interparticle attraction and makes them move apart. This causes the matter to expand and change its state from solid to liquid or from liquid to gas.
Decreasing the temperature decreases the kinetic energy of the particles, which increases the interparticle attraction and makes them move closer. This causes the matter to contract and change its state from gas to liquid or from liquid to solid.
Effect of pressure
Pressure is the force exerted by the particles of matter on a unit area. The higher the pressure, the more forceful the collisions between the particles are. This affects the state of matter in two ways:
Increasing the pressure decreases the interparticle space, which increases the interparticle attraction and makes them move closer. This causes the matter to contract and change its state from gas to liquid or from liquid to solid.
Decreasing the pressure increases the interparticle space, which decreases the interparticle attraction and makes them move apart. This causes the matter to expand and change its state from solid to liquid or from liquid to gas.
Evaporation
Evaporation is a type of vaporization that occurs at any temperature below the boiling point of a liquid. Evaporation is influenced by several factors, such as:
Surface area: The larger the surface area of a liquid, the more evaporation occurs.
Temperature: The higher the temperature of a liquid, the more evaporation occurs.
Humidity: The lower the humidity of air, the more evaporation occurs.
Wind speed: The higher the wind speed, the more evaporation occurs.
Evaporation causes cooling because it takes away heat energy from the liquid and leaves behind cooler molecules.
Conclusion
Summary of the chapter
In this chapter, we learned about matter and its properties. We learned that:
Matter is anything that has mass and occupies space.
Matter can be classified based on its physical state and composition.
Matter is made up of very small particles that have some characteristics that determine its physical nature and behaviour.
Matter can exist in three main states: solid, liquid, and gas.
Matter can change its state by changing the temperature or pressure.
Evaporation is a type of vaporization that occurs at any temperature below the boiling point of a liquid and causes cooling.
Importance of the chapter
This chapter is important because it helps us to understand:
The basic concept of matter and its classification.
The structure and properties of matter at microscopic level.
The phenomena related to change of state of matter in our daily life.
The factors affecting evaporation and its applications in cooling devices.
FAQs
Here are some frequently asked questions and answers related to this chapter:
What is the difference between boiling and evaporation?
What is the melting point and boiling point of water?
What is sublimation? Give an example.
What is latent heat? Why is it called latent?
What are the effects of evaporation on the weather and climate?
Answers:
Boiling is the process of changing a liquid into a gas at its boiling point, while evaporation is the process of changing a liquid into a gas at any temperature below its boiling point. Boiling occurs throughout the liquid, while evaporation occurs only at the surface of the liquid.
The melting point and boiling point of water are 0C and 100C respectively at normal atmospheric pressure.
Sublimation is the process of changing a solid directly into a gas without passing through the liquid state. For example, dry ice (solid carbon dioxide) sublimes into carbon dioxide gas when exposed to air.
Latent heat is the amount of heat energy required to change the state of a substance without changing its temperature. It is called latent because it is hidden or stored in the substance and does not affect its temperature.
Evaporation affects the weather and climate by increasing the humidity and cloud formation in the air, which in turn affect the precipitation and temperature patterns.
I hope you enjoyed reading this article and learned something new. If you want to download this chapter as a PDF file, you can click on this link: [Class 9 Science Chapter 1: Matter in Our Surroundings]. 44f88ac181
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