1 mole = atomic mass = 6.022 x 10²³ atoms
Now mass of one atom of M = 3.05 x 10^-22
Now mass of 6.022 x 10²³ atoms of M =  3.05 x 10^-22 x  6.022 x 10²³ g = 183.7 g
Mass of 1 mole or atomic mass of M = 183.7 g
This could be tungeten (W)

Step 1: Pass the mixture through a filter paper, water and oil will pass through, iron and sulphur will be left as a residue.
Step 2: The liquid separated is a mixture of water and oil. Take it in a separating funnel. Oil is generally lighter and makes the upper layer. The water, the lower layer can be poured out. Oil will remain in the funnel.
Step 3: Dry the solid residue. Pass a magnet over the mixture. Iron filings get stuck to the magnet whereas sulphur remains unaffected. Thus iron and sulphur get separated. Water and oil are compounds. Iron and sulphur are elements.

(i) 50+273=323K
(ii) Activity Take little amount of water in three containers which have different surface areas. Keep hem in sunlight for 2 h. Measure the volume of water left in all three containers.
Observation The amount of water left will be least in container having largest surface area among them.
Conclusion Greater the surface area, more will be the rate of evaporation.

(i) Liquid diffusing into solid.If we put a drop of ink on the centre of a clean blotting paper, we find the liquid spreads out by diffusing into the blotting paper which is a solid.
(ii) Solid diffusing into liquid.When we put a crystal of potassium permanganate in water, slowly the colour of potassium permanganate spreads throughout water.
(iii) Diffusion of a solid into a solid.Diffusion of solids into solids is very very slow.So diffusion of a solid into other solids is rare and very small.When we write on a blackboard with a chalk, we can easily clean it.But if it is left uncleaned for few days, it becomes difficult to clean the blackboard.This is because there is a slight diffusion of chalk particles.i.e., solid into the solid blackboard.

Homogeneous mixtures
(a) Solid solution. Alloys, e.g., brass, steel, bronze.
(b) liquid solution. Sugar solution in water, seawater, alcohol in water.
(c) Gaseous solution. Air, natural gas.
Heterogeneous mixtures
(a) Solid + Solid Sugar and sand, iron filings and sulphur, copper sulphate and potassium permanganate
(b) Solid +  Liquid Pastes, suspensions, etc.
(c) Solid + gas Smok
(d) Liquid + Liquid Milk, emulsions.
(e) liquid + Gas Soap bubbles.

(a) 300K = 300-273=\(27°C\)
(b) 573K = 573-273= \(300°C\) 

(a) Naphthalene has the property of sublimation.So even at room temperature, it evaporates to vapours.
(b) the molecules of gas are continuously moving at random either striking among themselves or with the walls of the container.The pressure on the walls of container is the force per unit area with which the moving gas particles strike per unit area of the containing vessel.

(a) Freezing point of water is below room temperature and boiling point is above room temperature.
(b) A gas occupies all the space available to it.

Solid -steel, rubber, glass
Liquid -Blood, oil, honey, kerosene, LPG
Gas -Air, carbon dioxide, CNG, nitrogen, oxygen.

An atom of Na has a total of 11 electrons. Its electronic configuration is 2, 8, 1. But, Na⁺ ion has one electron less than Na atom i.e., it has 10 electrons. Therefore, 2 electrons go to K-shell and 8 electrons go to L-shell, thereby completely filling K and L shells.

(a) Electron distribution of B = 2, 8, 6
(b) Electronic distribution of A is 2, 8, 1 and so its valency is +1.
(c) Since B contains 16 protons and so its atomic number is 16.
(d) Mass number of D = Number of protons + number of neutrons
= 17 + 22 = 39.

(i) 2O - Two atoms of oxygen
(ii) O₂ - One molecule of oxygen
(iii) O₃ - One molecule of ozone
(iv) H₂O - One molecule of water

A molecule is usually formed when at leats two elements of the same or different kinds combine.If two or three atoms of the same kind of element combine, then it is referred to as molecule of an element or simply molecule.For example, molecule of oxygen is formed by the combination of two oxygen atoms.For example, a molecule or a compound of carbon dioxide is formed by the union of one carbon atom and two oxygen atoms.However, the noble gases consist of molecules of single atoms only.For example, helium exists as He.

(a) Crystallization or evaporation
(b) Sublimation
(c) Centrifugation or sedimentation
(d) Chromatography
(e) centrifugation
(f) Separating funnel
(g) Filtration
(h) Magnetic separation
(i) Winnowing
(j) Centrifugation.

(i) Silver - elements
(ii) Methane - compound
(iii) Water - compound
(iv) Mecury : Element.

Crystallization is a process that separates a pure solid in the form of its crystals from a solution. Crystallization is better than evaporation because
(i) In evaporation, some solids may decompose on heating.
(ii) Evaporation can be used with completely non-volatile solids.
(iii) Some impurities may go with the filtrate, which on evaporation would contaminate the solid.

The illumination of a beam of light due to scattering on collision with certain particles is called the Tyndall effect.
In dense forests, Particularly in the early morning, there is fog, i.r. tiny water droplets are suspended in the air. These droplets are large enough to scatter beam of light. This is why the Tyndall effect can be observed when sunlight passes through dense forests.

(a) Mass percentage of NaCl \({15\over215}\times=6.98\) % 
(b) Solute: Co₂; solvent Water.

The amoeba obtains its food by the process of endocytosis. The flexible cell membrane engulfs the particle with the help of it's pseudopodia and then forms a vacuole around it. When the food is trapped the amoeba secretes digestive enzymes which digest the food.

Mass of one mole of water molecule = 18 g
Then, mass of 0.5 mole of water molecules = 0.5 x 18 g = 9 g

The mass of 10 moles of sodium sulphite (Na₂SO₃) is
= 10 x [2 x 23 + 32 + 3 x 16] g
= 10 x 126 g
= 1260 g