ICSE Class 9 Chemistry Chapter 01 Matter and Its Composition Law of Conservation of Mass

Chapter 1

Matter and Its Composition - Law of Conservation of Mass

Latest Syllabus - Scope of Syllabus - Matter & Its Composition - Law of Conservation of Mass

Matter and its Composition: Law of conservation of mass

(i) Explanation of change of state of matter on the basis of Kinetic Theory of Matter. Main Postulates of Kinetic Theory of Matter and explanation of change of state on the basis of Inter-particle space and Inter-particle attraction and collision.

(ii) Law of Conservation of Mass. Statement and explanation with examples.

A. Introduction - To Chemistry

Chemistry - A Definition

Chemistry deals with the study of behaviour of - matter

Chemistry is concerned with the - Composition, structure and properties of matter and the phenomenon which occurs when different kinds of matter undergo changes.

Teacher's Note

Chemistry helps us understand why a cup of hot tea cools down over time and how the sugar we add dissolves completely into the liquid.

Chemistry - A Brief History

Around 400 B.C. - Matter - its behaviour & nature were developed and conclusions drawn.

Fourth century B.C. - Aristotle & Plato - put forth their element theory to resemble the nature of matter.

Before 16th century - Alchemy - A new school of Chemistry was developed where - alchemists - were inspired by the changes in matter.

Modern Chemistry

In 1661 - Robert Boyle - studied the concepts of matter including elements & gases & their behaviour

In 1774 - A. L. Lavoisier - ushered in the quantitative era of Chemistry.

In 1807 - John Dalton - postulated his famous - atomic theory.

17th & 18th century - Henry Cavendish, Humphry Davy, Joseph Priestley - enhanced the developments in study of matter & Chemistry.

By end of 19th century - Atom - Its divisibility into sub-atomic particles was established which laid the foundation to newer concepts in Chemistry.

Teacher's Note

Learning the history of chemistry shows how scientists gradually discovered that matter is made of tiny invisible particles called atoms, which is similar to how we slowly learn about things around us.

Chemistry - Basic Divisions

Chemistry is a broad science with basic divisions as a result of its diversity

Inorganic Chemistry - A very wide branch which includes study of matter - elements and compounds except for those of carbon.

Organic Chemistry - The branch is devoted to the study of carbon & its numerous compounds.

Analytical Chemistry - The branch deals with identification and determination of the composition of specimens of matter and for devising efficient analytical techniques and procedures for chemical reactions.

Physical Chemistry - The branch is concerned with theoretical aspects of Chemistry. Physics is used to explain various chemical phenomenon.

Biochemistry - Deals with substances & chemical processes which occur in living matter.

Teacher's Note

Understanding these divisions helps us see that chemistry is everywhere - from understanding why metals rust (inorganic) to how our body processes food (biochemistry).

B. Introduction - To Matter

Matter and Its Composition

Definition of Matter - Matter is defined as anything which - occupies space and has mass and can be perceived by our senses. Matter is classified into - living and non-living.

Composition of Matter - Matter in any state is composed of small particles - molecules, atoms or ions.

Characteristics of Matter - Matter occupies space, which is called 'volume'. Matter has mass and weight, the quantity of matter represents its - 'mass' while the gravitational pull on matter, its - 'weight'. Matter can be perceived by physical senses i.e. touch, sight, smell etc. Examples of matter - Living things - animals & plant kingdom. Non-living things - earth, water, air etc.

States of Matter

All matter exists in one of the three states - i.e. solid, liquid or gaseous [vapour] classified on the basis of difference in certain - physical properties.

Solids - Solids have a definite mass, volume & shape and are highly rigid. They cannot flow, have high density and are almost incompressible & have any number of free surfaces.

Liquids - Liquids have a definite mass & volume but no definite shape and are less rigid. They can flow & take up the shape of the container in which they are stored. Liquids have comparatively less density, are very slightly compressible & have one upper surface.

Gases - Gases have a definite mass but no definite volume or shape, are not rigid at all. They can flow and take up the shape and volume of the container in which they are stored. Gases have least density, are highly compressible and have no free surfaces. [Vapour - is gaseous form under specific conditions but - solid or liquid under ordinary conditions.]

Change of State of Matter

Interconversion of matter involves - change of matter from one state to another and back to its original state. It is affected by changes in condition such as temperature, pressure etc.

Teacher's Note

When we boil water for tea, we observe the liquid transforming into steam (gas), and when we freeze water into ice, we see the liquid becoming solid - these are everyday examples of changes of state.

C. Main Postulates of - Kinetic Theory of Matter

Main Postulates of - Kinetic Theory of Matter

Composition of Matter - All matter in any state is composed of - small particles [molecules, atoms or ions].

Inter-particle Space - The particles are arranged - in a way such that spaces or gaps exist between them.

Inter-particle Attraction - The particles - attract each other with a force. The inter- particle attraction - decreases with increasing distance and vice-versa.

Energy Possessed by - Particles of Matter - Kinetic energy - The particles are in continuous random motion and possess kinetic energy. The kinetic energy of the particles - increases on application of heat [thermal energy] and the particles move more randomly. Potential energy - Particles interact and possess potential energy also.

Solids - Inter-particle Space & Inter-particle Attraction

Inter-particle Space - Particles are closely packed & can vibrate about their mean positions only. Hence solids do not flow, are rigid and have definite shape and volume. Inter-particle space between the particles is - minimum.

Inter-particle Attraction - Inter-particle attraction between the particles is - maximum

Energy Possessed by - Particles of Matter - Kinetic energy of molecules in a solid is - least.

Liquids - Inter-particle Space & Inter-particle Attraction

Inter-particle Space - Particles are comparatively less compact and the molecules are - free to move within the liquid, but do not leave the liquid. Hence liquids can flow, have a definite volume and are less rigid. Inter-particle space between the particles is - slightly more than solids.

Inter-particle Attraction - Inter-particle attraction is - less compared to solids.

Energy Possessed by - Particles of Matter - Kinetic energy of molecules in a liquid is - large.

Gases - Inter-particle Space & Inter-particle Attraction

Inter-particle Space - Particles [atoms/molecules]-show minimum compactness and particles are free to move in any direction, hence can fill any space. Gases have no definite shape or volume, can flow & are easily compressible. Inter-particle space between the particles is - comparatively very large.

Inter-particle Attraction - Inter-particle attraction is - negligible.

Energy Possessed by - Particles of Matter - Kinetic energy of molecules in a gas is - very large.

Teacher's Note

The kinetic theory explains why solid ice cubes keep their shape, water flows and adjusts to any container, and steam from a boiling kettle spreads throughout a room - each state has different particle spacing and movement.

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