Solutions-Class 8-Science-Chapter-6-Composition of Matter-Maharashtra Board

A. The intermolecular force is  maximumin the paricles of solid.

B. Solids retain their voume even when external pressure is applied. This property is called elasticity.

C. Matter is classified into the types mixture, compound and element by applying the criterion Chemical composition of matter.

D. Matter that contain two or more constituent substances is calledmixture.

E. Milk is an example of type of matter called heterogeneous mixture.

F. Water, mercury and bromine are similar to each other, because three are liquids.

G. Valency of carbon is 4 and that of oxygen is 2. From this, we understand that there are 2 chemical bond/bonds between the carbon atom and one oxygen atom in the compound carbon dioxide.

1. Brass is odd one out because it is an alloy and gold, silver, copper are element.
2. Hydrogen is odd one out because it is an element and others are compound.
3. Carbon is odd one out because it is an element and others are mixture of various elements.
4. Petrol is odd one out because others are inorganic compounds.
5. Sugar is odd one out because others are inorganic compounds
6. Carbon is odd one out because it has 4 valence electrons and others have 1 valence electron.

Photosynthesis is a chemical process through which plants, some bacteria and algae, produce glucose and oxygen from carbon dioxide and water, using only light as a source of energy, which is absorbed by chlorophyll.

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O2

Four compounds in this process are as follows:

1.Carbon dioxide = Inorganic compound

2.Water = Inorganic compound

3.Glucose = organic compound

4.Chlorophyll = complex compound

Brass is an alloy it contains 70% copper, and 30% zinc.

Copper is solvent with largest proportion

Zinc is solute in smaller proportion

The solution is Brass

Characteristics of mixtures from above information are:

1.Constituent substances of a mixture (proportion of salt in water) do not combine chemically.

2.The proportion of constituent substances present by weight in a mixture can be variable.

3.The constituent of mixture can be separated by physical process.

A. Liquid element = mercury (H_g), bromine(Br₂)

B. Gaseous element = oxygen(O₂), nitrogen(N), hydrogen(H)

C. Solid element = sodium(Na), carbon (c), aluminium(Al)

D.Homogeneous mixture = sugar in water, corn oil, Sea water.

E. Colloid = milk, blood, jelly.

F. Organic compound = glucose, urea, carbohydrates.

G. Complex compound = chlorophyll, hemoglobin, cyanocobalamine.

H. Inorganic compound = limestone, rust, common salt, Soda.

I. Metalloid = silicon, germanium, arsenic.

J .Element with valency 1 = sodium(Na), potassium(K), chlorine(Cl).

K. Element with valency 2 = magnesium(Mg), calcium(Ca)

• Water is compound of hydrogen and oxygen.
• Hydrogen is combustible and oxygen helps combustion.
• Though water is made up of two atoms of hydrogen and one atom of oxygen by forming an ionic compound, it does not possess the characteristics of them because a compound does not have the properties of its constituent elements.
• Therefore, water has its own properties, which helps to extinguish fire.

Colloidal solution is heterogeneous. Constituent substances of a colloid cannot be separated by ordinary filtration because the size of the particles in a colloids (or colloidal solution) is bigger than those in a true solution but smaller than those in suspension. It is in between 1μ to 100μ in diameter. The pore size of ordinary filter paper is more than 100μ due to which colloidal particles are passed through the pores of a filter paper. Therefore we prefer to use filter paper so that, filtration of colloidal particles take place easily.

• Lemon sherbat is a mixture. It is made up of lemon juice, sugar, salt and
• Formation of lemon sherbat does not involve any chemical reaction.
• The constituents of sherbat retain their individual properties.
• Hence, lemon sherbet is sweet, sour and salty to taste and it can be poured in a glass.

A solid matter has the properties of definite shape and volume because of the following reasons:

• The forces among the constituent particles (atom/molecules) are called intermolecular forces.
• In solids these forces are strong enough to keep the particles together in fixed positions, as a result solids have a definite shape and volume element.

Step 1 : Write the symbols of the elements.                       

Step 2 : Write the valency below the respective elements.       

Step 3 : Cross-multiply symbols of elements with their respective valency.
 
Step 4 : Write down the chemical formula of the compound.

The molecular formula is CCl₄

Step 1 : Write the symbols of the elements.                       

Step 2 : Write the valency below the respective elements.       

Step 3 : Cross-multiply symbols of elements with their respective valency.

Step 4 : Write down the chemical formula of the compound.

The molecular formula is NH₃

Step 1 : Write the symbols of the elements.        

Step 2 : Write the valency below the respective elements.       

Step 3 : Cross-multiply symbols of elements with their respective valency.

The molecular formula is CO₂

Step 1 : Write the symbols of the elements.                       

Step 2 : Write the valency below the respective elements.       

Step 3 : Cross-multiply symbols of elements with their respective valency.

Step 4 : Write down the chemical formula of the compound.
The molecular formula is CaO