Question

important questions from class 9 science

Answer 1

1.Which one of the following sets of phenomena would increase on raising the temperature?
(a) Diffusion, evaporation, compression of gases
(b) Evaporation, compression of gases, solubility
(c) Evaporation, diffusion, expansion of gases
(d) Evaporation, solubility, diffusion, compression of gases
2.A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C? Comment.

etc

Answer 2

Matter in our surroundings.

List the important characteristics of matter

• Difference among solid, liquid and gas.

• List any five physical properties of liquids

• Classify the matter in terms of physical state and composition

• Simple and clear-cut definitions along with the differences between the following terms:

Evaporation
Sublimation
Condensation
• Difference between latent heat of fusion and latent heat of vaporization

• Definitions of melting point, boiling point and freezing point

• Read clearly about the sublimation process.

• Identify the matter from the given terms:

Chair, Air, Love, Smell, Hate, Almonds, Thought, Cold, Cold drinks, Smell of perfume

• The smell of hot sizzling food reaches you several meters away, but to smell the cold food you have to get close to it. Give the logical explanation for the same

• What is Diffusion, and why gases diffuse rapidly?

• The mass per unit volume of a substance is called density (density=mass/volume). Arrange the following in order of increasing density:

Air, Exhaust from chimneys, Honey, Water, Chalk, Cotton, and Iron

• Explain the application of compressibility in gases with an example

• Define the term evaporation

• Mention the uses of LPG and CNG

• What is SI unit of temperature? Give mathematical relation also.

2 is matter around us pure
Name the elements are in liquid state at room temperature.

Q. Separate the following as mixture or compound.

(i) Blood

(ii) Common salt

(iii) Sugar

(iv) Brass

Q. Solutions do not exhibit Tyndall effect. Reason

Q. What are the characteristics of mixture?

Q. When we open the cap of an any carbonated beverage (like Pepsi drink), why does excess of bubbles come out?

Q. What are suspensions? Explain with an example..

3 atoms and molecules.

Q. Magnesium and oxygen combine in the ratio of 3:2 by mass to form magnesium oxide. How much oxygen is required to react completely with 12 g of magnesium?

Q. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?

Q. Which of the following statements is NOT true about an atom?

(a) Atoms are the building blocks from which molecules and ions are formed.

(b) Atoms cannot exist independently.

(c) Atoms are neutral in nature.

(d) Atoms combine together to form matter that we can see, feel, or touch.

Q. A sample of vitamin C is known to contain 2.58 ×1024 oxygen atoms. How many moles of oxygen atoms are present in the sample?

Q. If bromine atom is available in the form of, say, two isotopes 7935Br (49.7%) and 8135Br (50.3%), calculate the average atomic mass of bromine atom.

Q. Which has more number of atoms, 100g of N2 or 100 g of NH3?

Q. Calculate the relative molecular mass of water (H2O)

Q. Calculate the formula unit masses of ZnO, Na2O, and K2CO3.

[Given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u]

Q. Write the chemical formulae of the following.

(a) Magnesium chloride

(b) Calcium oxide

(c) Copper nitrate

(d) Aluminium chloride

(e) Calcium carbonate.

4 structure of an atom

Q. What are the limitations of Rutherford’s model of the atom?

Q. Compare all the proposed models of an atom given in this chapter.

Q. If bromine atom is available in the form of, say, two isotopes 35Br79 (49.7%) and 35Br81 (50.3%), calculate the average atomic mass of bromine atom.

Composition of the nuclei of two atomic species X and Y are given as under:

X Y

Protons = 6 6

Neutrons = 6 8

Give the mass numbers of X and Y. What is the relation between the two species?