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CBSE class 9 science notes chapter-2 is matter around us pure
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Is matter around us pure notes pdf class 9
What is Matter?
Anything in the universe that has mass and takes a space is known as Matter. On the basis of physical classification, it can be classified into solid, liquid, and gas. On the other hand, in chemical classification, the matter can be classified into Elements, Compounds, and Mixtures.
➢ Pure substances can be either all one type of atom (element) or all one type of all bonded atom (Compound).
➢ Pure substances have definite chemical & physical properties.
➣ It has a definite composition that cannot be broken into two or more simple substances by physical process.
➣ Pure Substances divided into two parts. 1. Element 2. Compounds
What is an Element?
Element is a type of pure substance which is consists of only one type of fundamental particles or atoms. It cannot be further broken down into smaller pieces by chemical or physics method.
For Example:- Oxygen, Hydrogen, Carbon, Nitrogen, Copper, etc.
The element has three more major parts.
Physical and chemical properties of Metals
- They show the luster (shiny) property.
- Metals are malleable and ductile in nature.
- Metals are good conductors. They conduct heat and electricity.
- Most metals are solid at room temperature. (Except Mercury)
- All metals are hard in nature except Sodium & Potassium.
- Metals have a high melting point and high density.
- Example of Metals:- Copper, Iron, Mercury, Silver, Gold, etc.
Physical and chemical properties of Non-Metals
- Non-Metals are poor conductors of heat & electricity.
- These are brittle in nature.
- Non-Metals have a low melting point and low density.
- Non-Metals have little or no metallic luster.
- These are non-malleable and non-ductile.
- Example of Non-Metals:- Carbon, Oxygen, Sulpher, Hydrogen
Physical and chemical properties of Metalloids
Metalloids have properties that lie between metals and non-metals. It exhibits some metallic and some nonmetal properties.
- These are good semiconductors.
- They are solid in nature.
- It has high brittleness.
- They show metallic luster property.
- Example of Metalloids:- Boron, Silicon, Germanium, etc.
What is a Compound?
When two or more different elements are added in a fixed ratio, they form a compound. Compounds elements combined in a specific ratio that is not separated by physical process.
Examples of compounds:- Sugar, (H2O), oxygen (O2), Nitrogen dioxide (NO2), etc.
Since compounds are combined by two or more basic elements in a constant ratio, they can only be separated by chemical methods (Electrolysis).
What is a Mixture or Impure Substances?
When two or more elements or compounds combine in a certain proportion or quantity, a substance formed in this way is called a Mixture.
Types of Mixture?
Mixtures can divide into two parts.
1. Homogeneous Mixture
A mixture in which all the properties of each part are equal is called a homogeneous mixture.
It is a mixture that has a uniform composition throughout its mass or constituent is uniformly distributed throughout the mixture is called Homogeneous mixture.
For Example:- Mixture of Sugar+Water, Mixture of Salt+Lemon+Water
2. Heterogeneous Mixture
A mixture whose properties are not the same for each part is called a heterogeneous mixture. Its composition is not the same throughout its mass. The separation boundary between its various components is clearly visible.
For Example:- Mixture of Sand + Water
Solution, Suspension, Colloidal
A homogeneous mixture of two or more components or substances is called a solution. A solution has two main components.
Solution= Solute + Solvent
Solute:- In a solution composed of two components of the same physical state, the component which is in a small amount is called the Solute.
Ex- In a solution of Salt and Water, Salt is solute.
Solvent:- The component which is usually present in excess in a solution is called the solvent. The solvent determines the physical state of the solution.
Ex- In a solution of Salt and Water, Water is solvent.
Properties of Solution
➢ The solution is a homogeneous mixture of two or more components.
➢ Solutes cannot be separated from the solution by the filtration process.
➣ The particles of the solution are so small that we cannot (below 1 nanometer in diameter) see them with the naked eye.
➣ The solution is stable and transparent.
➢ Due to the particle size of the solution being very small, they are unable to scatter the light beam. That is why the path of light is not visible in the solution.
Major terms related to a Solution
1. Dilute Solution:- The solution in which the amount of solute is less than that of solvent is called a dilute solution.
2. Concentrated Solution:- The solution in which the amount of solute is more than the amount of solvent is called a concentrated solution.
3. Saturated Solution:- A solution in which no more quantity of solute can be dissolved at a certain temperature and pressure is called a Saturated Solution.
4. Unsaturated Solution:- A solution in which a more amount of solute can be dissolved at a certain temperature is called an Unsaturated solution.
5. Solubility:- At a certain temperature and pressure, the maximum amount of solute dissolved in a 100 g solvent is called the solubility of the solute in that solvent.
Define Concentration of Solution
The amount of solute present in a unit volume of a solution is called the concentration of the solution. The composition of any solution is expressed in terms of concentration.
Concentration of Solution:-
Here are two formulas for measuring the concentration of a solution.
Suspension and its properties
In a heterogeneous solution, the particles of a solid do not dissolve in the liquid but are dispersed without dissolving in the liquid, and such solutions are Suspensions.
Properties of Suspension
➢ It is a heterogeneous mixture of two or more components.
➢ The solute particle size dissolved in the solvent is larger than the true solution particles (greater than 100 nm), which is visible with the naked eye.
➣ Due to the large size of the suspension particle, these particles show the Tyndall effect.
➣ If the suspension is released without any disturbance, its particle settles down. In this situation, the suspension particles do not show the Tyndall effect.
➢ The size of the suspension particle is more than 100 nanometer.
➢ Their particles can be separated by the filtration method.
Chapter 1 Notes:-Matter in Our Surroundings
Colloids or Colloidal Solution
Define Colloidal Solution:-
A mixture with properties between homogeneous and heterogeneous mixtures, whose particles are uniformly dispersed in a solution, is called a Colloidal Solution.
Properties of Colloidal Solution
➢ It is a heterogeneous mixture of two or more components.
➢ The diameter of the dispersed phase particle is between 1 and 100 nanometers.
➣ The particles of the colloidal solution show the Tyndall effect.
➣ The particle size of the colloidal solution is larger than the true solution and smaller than the suspension particle.
➢ If the colloidal solution is left undisturbed, its particles do not settle down.
➢ Their particles cannot be separated by filtration method whereas they can be separated by centrifugation method.