Materials can be classified according to their several properties.
- Hardness or Softness
- Heaviness or lightness
- Good conductor of Heat
- Good conductor of Electricity
On the basis of their appearance, all materials are classified into two ways,
1) Material having lustre (shiny appearance)
Metals like Gold, Silver, Copper, Aluminium, Iron, Steel and Diamond are showing shiny appearance i.e. they are lustrous in nature.
Sometimes it reacts with atmospheric things like air, water and gets rusted called corrosion.
2) Materials do not have lustre (shiny appearance)
Cotton, wood, plastic, powdered form chemicals, rubber and paper this are non lustrous things.
They are showing dullness/lightness in appearance.
Question 1) Name of that exception Non-metal which has Lustre.
Answer– Iodine. It is non-metal but has lustre property.
Hardness or Softness-
On this property material is divided into two categories.
1) Soft MaterialsMaterials which can be compressible easily are called Soft Materials.
They are easily molded and stretched. For example, cotton, wax, rubber, clothes, flowers and Sponge are soft in touch.
2) Hard MaterialSome other materials which cannot be compressible, this called Hard
They are difficult to mould and cannot b stretchable. For example, piece of iron, wood, and piece of concrete, rock is hard in touch.
Heaviness or lightness-
Density- The density of a substance is its mass per unit volume.
According to density we can decide the heaviness and lightness of the substance.
Density simply means we can measure their heaviness according to their size and shape. It may be higher and lower both.
Substance which is heavier than water means have a higher density than water and substance which is lighter than water means have lower density than water.
If object is dense than water it will confirmly sink and if object is less dense than water it will confirmly float.
In this above image according to their densities object will sink and float.
Question 1) Is Oil floating on water. Give reason?
Answer- oil and water is not mix with each other so oil forms a layer on water because oil is less dense than water therefore, oil floats on water.
Question 2) why some liquid-liquid medium materials is not mixed with each other?
Answer- The reason is both are liquid but their densities are different therefore, they do not mix with each other.
Question 3) Name the two liquids which do not dissolve in water and are heavier than water.
Answer- Corn-syrup and Glycerin.
Materials have different-different solubility in water. According to their Solubility, they can be soluble, insoluble, miscible and immiscible.
A substance which is dissolved in water called as soluble substances. For example- salt, sugar, food colours, etc.
Substances which do not dissolve in water are called as insoluble substances. Even gases are also soluble in water.
For example- sand, saw dust, leaves, honey, etc.
Substances may be Miscible and Immiscible both, those liquid which mix well with water called as a miscible substances and substances which do not mix well with water is called as immiscible substances.
Solute + solvent = Solution.
Solvent is the substance in which solute can dissolve and the solute is a substance which dissolve in solvent and make a solution.
Question 1.Why water is called as Universal Solvent?
Answer- Water has ability to dissolve mostly substances in it therefore it called as Universal solvent.
Question 2) Give few examples of Miscible & immiscible solution.
Answer- Miscible solution- sugar & water, salt & water, Milk, etc.
Immiscible solution- sand +water, alcohol and water, salt+ alcohol, Carbonated drink + milk
Question 3) Give example of soluble Gases.
Answer- Oxygen, carbon dioxide
Question 4) Give example of insoluble gases.
Answer- Hydrogen & nitrogen.
On the basis of visibility substances can be divided in three types i.e. transparent, translucent and opaque.
Material through which things can be passing light source and subject seen clearly is called as Transparent.
For example- Glass, Fresh Water.
Material through which can be passing light source but subject seen blur visible is called as Translucent. This kind of material can’t be seen clearly.
For example- Wax or Oil paper, Frosted Glass, Muddy water. Materials which do not allow to pass light source and subject is not visible is called as an Opaque.
For example- wood, thick paper, metal, etc.
Question 1) what are opaque objects?
Answer- Opaque object either absorb or reflect most of the light which is falling on it, that objects called as opaque objects.
Question 2) Name a material which is actually translucent but you can make it Opaque.
Answer- Tissue paper or any thin cloth is translucent. We can make it
Opaque by adding some colours or place melted wax on
All substances are made up of matter and matter exists in three states.
E.g. Solid, Liquid and Gaseous.
Solid have fixed shape as well as volume. Particals are closely packed.
Liquid does not have fixed shape but has definite volume. Liquid has ability to adjust with respected container and take their shape according to this. Particles are lossely packed as compare to solid.
Gases does not have fixed shape and volume. It is freely movable in atmosphere.
Material that allow it to flow through them is called as a good conductor of heat whereas some are do not allow it to flow is called as insulator.
In generally metals are good conductor of heat. Non-metals like plastic, glass, paper are the insulators of heat.
Question 1) Cooking pans are covered by plastic or wood material. Justify this sentence and explain the need of this cover.
Answer- Cooking pans are good conductors of heat that the reason we cooked our meal in it But they covered by plastic or wood handles because wood and plastic are bad conductors of heat. So it protects us from burning while cooking.
Conduction of electricity
Material that allowed to flow the electricity in it is called a good conductor of electricity just like example of copper. Copper is a one kind of a metal. It is used in electricity fitting because it is good conductor of electricity.