CBSE 9th Chemistry | The Matter-Nature and Behaviour (Very Short Answer Type Questions)

The Matter-Nature and Behaviour (Very Short Answer Type Questions)

Question 1. The earlier Indian Philosophers classified matter in the form of five basic elements. Name these five elements.

Answer.

The five basic elements are : Air, Earth, Fire, Sky and Water.

Question 2. According to modern view is matter continuous or particulate?

Answer.

Matter is particulate in nature i.e., Matter is made up of particles.

Question 3. What is the size of particles of matter?

Answer.

The particles of matter are very small. They are small beyond our imagination.

Question 4. What is diffusion?

Answer.

The intermixing of particles of two substances on their own is called diffusion.

Question 5. What is the effect of temperature on the speed of particles of matter?

Answer.

As temperature rises, particles move faster i.e., the speed of particles increases.

Question 6. Name major characteristics of solid state of matter.

Answer.

Solid state is characterised by having a definite shape, distinct boundaries, rigidity and incompressibility.

Question 7. By what name is the space occupied by a substance known?

Answer.

The space occupied by a substance is called volume.

Question 8. What is the common unit of volume?

Answer.

The unit of volume is cubic meter (m3)

The common unit is litre  (L)

1L = 1dm3

= 1000 ml

Question 9. The particles of matter are always in motion and due to this motion they posses some energy. By what name is this energy known?

Answer.

The energy possessed by a particles by virtue of its motion is known as kinetic energy (K.E.).

Question 10. Why do solids have a rigid or fixed shape?

Answer.

The particles of solids only vibrate at their mean position and they possess a low kinetic energy. Due to this solids have a rigid or fixed shape.

Question 11. What are the characteristics of a liquid?

Answer.

The liquid state is characterised as having fluidity, low compressibility and no definite shape or boundaries.

Question 12. Are liquids rigid?

Answer.

No, liquids are not rigid. They are fluid because they can flow.

Question 13. Arrange the particles of solids, liquids and gases in the decreasing order of kinetic energy possessed by them.

Answer.

Gases > Liquids > Solids.

Question 14. How does diffusion varies with density of liquid?

Answer.

More the density lesser is diffusion.

Question 15. Name any property that is shown by naphthalene but not by sodium chloride.

Answer.

Both are solids but naphthalene is sublime substance and shows the property of sublimation. This property is not shown by sodium chloride.

Question 16. What is pressure at sea level?

Answer.

The pressure that exists at sea level is taken as 1 atmosphere or 760 mm of mercury.

Question 17. Zero °C represents the freezing point of water or the melting point of ice?

Answer.

It represents both freezing point as well as melting point.

Question 18. Boiling point of alcohol is 65°C. What is the boiling point of alcohol in Kelvin scale?

Answer.

65°C = (65 + 273)K=338K.

On kelvin scale the boiling point of alcohol is 338 K.

Question 19. Define condensation.

Answer.

It is the process of conversion of vapour (gas) to liquid on cooling (decreasing temperature).

Question 20. What is dry ice?

Answer.

Solid carbon di-oxide (C02) is known as dry ice.

Question 21. Why can’t the solids be compressed much?

Answer.

The intermolecular space between the particles of solids is very less, because of this solids can not be compressed much.

Question 22. Arrange the solids, liquids and gases in the increasing order of inter molecular forces of attraction.

Answer.

Gases < Liquids < Solids.

Question 23. Arrange the solids, liquids and gases in the decreasing order of interparticle space.

Answer.

Gases > Liquids > Solids.

Question 24. Why is the property of diffusion not shown by solids?

Answer.

Since the particles of solids do not move much so the solids do not show the property of diffusion.

Question 25. By what name is the substance known in case there occurs a diffusion of a solid in a solid which is a rare phenomenon.

Answer.

It is known as solid-solid solution or alloy.

Share

Chemistry IX | Matter-Its Nature and Behaviour: Mole Concept | Part 3

Matter-Its Nature and Behaviour: Mole Concept

INTRODUCTION

Atomic Mass

· The average relative mass of an atom of an element as compared to the mass of an atom of carbon (C12) taken as 12. In other words atomic mass is a number which expresses as to how many times an atom of the element is heavier than 1/12th of the mass of carbon atom. Therefore,

· Atomic mass = clip_image002

Average Atomic Mass

· It has been found that majority of the elements occur as several isotopes. Isotopes are the different atoms of the same element possessing different atomic masses but same atomic number. The atomic mass of each isotope is determined separately and then combined according to the ratio of their proportions of occurrence. This is known as average atomic mass. E.g., Boron occurs in nature in the form of two isotopes B10, B11 with atomic mass 10 and 11 in the ratio of 1 : 4 respectively. Therefore Average atomic mass of carbon

= clip_image004

= clip_image006

Gram Atomic Mass

· The atomic mass of an element expressed in grams is the gram atomic mass or it is also called gram atom e.g. the atomic mass of oxygen is 16 amu, therefore gram atomic mass of oxygen is 16g.

Molecular Mass

· Molecular mass of a compound is defined as the weight of a molecule of the compound relative to a carbon atom, the atomic weight of which is supposed to be equal to 12.

Molecular mass of H2SO4 =

2 clip_image008 atomic mass of hydrogen + atomic mass

of sulphur + 4clip_image008[1] atomic mass of oxygen

= 2 clip_image008[2]1 + 32 + 4 clip_image008[3] 16 = 98

Gram Molecular Mass

· Molecular mass of a substance expressed in grams is called gram molecular mass. It is also known as gram molecule. e.g., molecular mass of N2 is 28 and its gram molecular mass is 28 gm.

Determination of the molecular weight

(i) By using Graham’s law of diffusion

clip_image014

r1 and r2 are the rates of diffusion of gases having molecular weights M1 and M2 respectively.

(ii) Victor Meyer’s method

V.D. = clip_image016 (Approx).

m grams of substance displaces x mL of air at NTP.

Equivalent Mass

  • An equivalent mass of a substance is defined as the amount of it which combines with 1 mole of hydrogen atoms or replaces the same number of hydrogen atoms in a chemical reaction. The equivalent mass of a substance expressed in grams is called gram equivalent. e.g., in the compounds like H2O, NH3, CH4, one mole of hydrogen combine with clip_image018 mole of O, clip_image020 mole of N and clip_image022 mole of C respectively Hence

Equivalent mass of O = clip_image024

Equivalent mass of N = clip_image026

Equivalent mass of C = clip_image028

Relation between Atomic weight, Equivalent weight and Valency

Equivalent weight = clip_image030

E = clip_image032

e.g., equivalent mass of H2SO4 is clip_image034 = 49

For Bases

E = clip_image036

For Ca(OH)2, E = clip_image038

For Salts

E = clip_image040

cations or anions

For Oxides

E = clip_image043

· In a redox reaction equivalent mass depend upon the number of electrons taking part in the reaction

E = clip_image045

Where n factor is total change in oxidation number of element in molecule

Determination of Equivalent weight

(i) Hydrogen displacement method :

Eq. wt. of the metal

= clip_image047

(ii) Oxide formation method :

Eq. wt. of element = clip_image049

where w1 = weight of element

w2 = weight of chloride

(iii) Chloride formation method :

Eq. weight of the element = clip_image051

where m1 = weight of element

m2 = weight of chloride

(iv) Metal displacement method : A more electropositive metal ‘B’ displaces less electropositive metal ‘A; from its salt solution.

clip_image053= clip_image055

Mole

· A mole is the amount of substance that contains as many particles as are present in 12 g of carbon – 12 isotope.

· ‘Mole may also be defined as “the amount of a substance in grams which contains 6.023 x 1023 units of that substance.

· 6.023 x 1023 particles of a substance weight equal to the molecular weigh of that substance in grams, therefore, 1 mole is the gram molecular weight of a substance :

Number of mole = clip_image057

= clip_image059

= clip_image061

Gram Molar Volume

· The volume occupied by 1 mole of a substance is called gram molar volume of the substance. The gram molar volume of perfect gas is 22.4 liters at STP or NTP. N.T.P. clip_image063 Normal temperature and pressure S.T.P. clip_image063[1] Standard temperature and pressure e.g., volume of 1 mole of H2 at STP = 22.4 L

STP = 22.4 L

Volume of clip_image022[1] mole of H2,

= clip_image067 = 5.6 L

Vapour Density

· Vapour density of a gas is the ratio of the mass of a certain volume of the gas to the mass of equal volume of hydrogen, measured under same conditions of temperature and pressure.

Vapour density = clip_image069

Molecular weight = 2 clip_image008[4] vapour density

Atomic weight = 2 clip_image008[5] clip_image073


Knowledge Update

– Equivalent weight of CO2, SO2 and SO3 is equal to clip_image075.

– Equivalent weight of acidic salt = clip_image077

– Mole wt. = 2 clip_image008[6] vapour density

Mole = clip_image080

Atomic wt. clip_image008[7] specific heat = 6.4 (approx)

Share