is the matter around us pure (full lesson short notes)
Answers
:short notes (hope it helps)
Anything which has mass and occupies space is called matter. It may be solid, liquid or gas.
Types of Matter
It is of two types :
1. Pure Substance
2. Impure substance
types of matter
1. Pure Substance: It may be defined as a material which contains only one kind of atoms or molecules.
Pure substances are again of two types:
(a) Elements (b) Compounds
(a) Elements:
Pure substances which are made up of only one kind of atoms are known as elements.
They cannot be split up into two or more simpler substances by any of the usual chemical methods.
For example: Iron, gold, silver, carbon, oxygen, nitrogen and sodium etc.
CBSE Class 9 Science, Is Matter Around Us Pure: Important Topics and Questions
Elements are further grouped into the following three categories:
(i) Metals, for example: Iron, copper, gold, sodium, silver, mercury, etc.
(ii) Non – metals, for example: Carbon, oxygen, sulphur, nitrogen, oxygen, hydrogen, etc.
(iii) Metalloids : Boron, silicon, germanium, etc.
Properties of Metals:
These are lustrous (shine).
They conduct heat and electricity.
All metals are malleable and ductile.
They are sonorous.
All metals are hard except sodium and potassium.
All metals are solids at room temperature except mercury which is a liquid.
Properties of Non-metals:
These are dull in appearance.
They are poor conductors of heat and electricity except diamond which is a good conductor of heat and graphite which is a good conductor of electricity.
They are neither malleable nor ductile.
They are generally soft except diamond which is the hardest natural substance known.
They may be solids, liquids or gases at room temperature.
Metalloids: The elements that have properties intermediate between those of metals and non-metals, are called metalloids.
(b) Compounds:
It is a form of matter formed by combining two or more elements in a definite ratio by mass.
It Can be decomposed into its constituent elements by suitable chemical methods
For example: Water (H2O), oxygen (O2), Nitrogen dioxide (NO2), etc.
2. Impure Substance: It may be defined as a material which contains only one kind of atoms or molecules.
It is also named as mixture.
Mixtures:
A mixture is a material which contains two or more different kinds of particles (atoms or molecules) which do not react chemically but are physically mixed together in any proportion.
Types of mixture
It is of two types:
(a) Homogeneous mixture (b) Heterogeneous mixture
S. No.
Homogeneous mixture
Heterogeneous mixture
1.
All the components of the mixture are uniformly mixed.
All the components of the mixture are not thoroughly mixed.
2.
No separation boundaries are visible.
Separation boundaries are visible.
3.
It consists of a single phase.
It consists of two or more phases.
4.
Example: Sugar dissolved in water
Example: Air, sand and common salt.
Difference between mixtures and compounds:
S. No.
Mixtures
Compounds
1.
Various elements just mix together to form a mixture and no new compound is formed.
Elements react to form new compounds.
2.
A mixture has a variable composition.
The compound has a fixed composition.
3.
A mixture shows the properties of its constituents.
Properties of a compound are totally different from those of its constituents.
4.
They do not have a fixed melting point, boiling point, etc.
They have a fixed melting point, boiling point, etc.
5.
The constituents can be seperated easily by physical methods
The constituents can be separated only by chemical processes.
Concentration of a Solution
It is defined as the mass of the solute in grams present in 100 grams of the solution.
Mathematical expression for concentration of solution:
concentration of solid in liquid, solid in solidsolution
In case of liquid solute in liquid solvent concentration can be expressed as:
concentration of liquid in liquid olution
Saturated Solution
A solution in which no more quantity of solute can be dissolved at a particular temperature
Unsaturated Solution
A solution in which more quantity of solute can be dissolved without raising its temperature .
Try thequestions:
Q1. What would it mean by saying a 15% of alcohol solution?
Q2. Calculate the concentration of a solution containing 2.5g of salt dissolved in 50g of water.
Q3. Name the different types of solutions along with an example for each.