Class 9

Chapter 1: States of Matter and Phase Changes (Solved Exercise Notes)

This is solved exercise notes for chapter 1: ‘States of Matter and Phase Changes’ of the new book for 9th Class Chemistry (Punjab Board – PCTB). These notes include solved multiple choice questions (MCQs), questions for short answers and constructed response questions.

1. Multiple Choice Questions

1. Matter is present in neon signs in the state of:

(a) Supercritical Fluid

(b) Plasma

(c) Gas

(d) Liquid Crystal 

2. Hazardous effects of shopping bags are studied in:

(a) Geochemistry

(b) Inorganic Chemistry 

(c) Analytical Chemistry 

(d) Environmental Chemistry

3. The man-made polymer is:

(a) Starch

(b) Polystyrene

(c) Protein

(d) Cellulose

4. The crystals of which substance has rhombic shape?

(a) Brass

(b) Sulphur

(c) Graphite

(d) Bronze

5. Which liquid among the following is a colloidal solution?

(a) Milk

(b) Slaked lime used for whitewash

(c) Vinegar solution

(d) Mixture of AgCl in water

6. Which of the following is a heterogeneous mixture?

(a) A solution of calcium hydroxide in water

(b) A solution of potassium nitrate in water

(c) Hot chocolate

(d) Concrete mixture

7. A state of matter whose properties are between those of liquids and crystalline solids:

(a) Liquid crystal

(b) Supercritical fluid

(c) Plasma

(d) Dark matter

8. When the tiny visible particles of a substance are dispersed through a medium, the mixture is named as:

(a) True solution

(b) Colloid

(c) Suspension

(d) Saturated solution

9. A solution of KClO3 has a solubility of about 13.2g per 100 cm³ at 40°C. How its solubility will be affected, if you decrease the temperature?

(a) The solubility will increase

(b) The solubility will decrease

(c) The solubility will remain the same

(d) The solubility will first increase with temperature and then it will decrease

10. You are studying the rate of hydrolysis of starch under different conditions of temperature. In which branch of chemistry will this topic fall?

(a) Organic Chemistry

(b) Analytical Chemistry

(c) Biochemistry

(d) Physical Chemistry

2. Questions for Short Answers

Q1. Why is there a need to divide Chemistry into many branches? Give three reasons.

Chemistry is divided into different branches due to these 3 reasons:
a. To understand the complex subject of chemistry better
b. To concentrate on a specific aspect of chemistry
c. To focus on distinct areas of study in chemistry

Q2. Reactions may take place due to electrons present outside the nucleus or they may take place inside the nucleus. Which branches of Chemistry cover these two types of reactions?

1. Reactions that involve the electrons of an atom are studied in physical chemistry.
2. Reactions that involve the nucleus of an tom are studied in nuclear chemistry.

Q3. What types of problems are solved in analytical chemistry?

Analytical chemistry solves three types of problems by giving us the following information about a matter:
1. What is it?
2. How much is it?
3. Is it pure?

Q4. Both graphite and graphene have hexagonal layered structures. What is the difference?

In graphite multiple layers of carbon atoms are stacked on top of each other, while graphene consists of only one layer of carbon atoms.

Q5. Why are supercritical fluids important?

Chemical reactions which are difficult to carry out in common solvents can easily be carried out in supercritical fluids.

Q6. In which state does matter exist in the Sun?

Matter in the sun exist in the state of plasma.

Q7. What is the importance of graphene?

Due to its tough, flexible and strong nature, graphene is used in very high-tech equipment such as sensors, batteries and vehicles.

Q8. Which form of matter do most of the material things in this world belong to?

Most of the material things in this world belong to the solid state of matter.

3. Constructed Response Questions

Q1. How does a supercritical state look like?

A supercritical state of matter is an intermediate state of matter. It is a highly compressed form of gas. Therefore, it looks somewhat like a liquid as well as a gas. Its particles are close together as in liquids but have very weak intermolecular forces like in gases.

Q2. In what way is plasma created in a fluorescent tube?

In a fluorescent tube, plasma is created by passing an electric current through a gas. The current ionizes the gas particles, which creates the plasma.

Q3. Most of the molecules we study in biochemistry are organic in nature. Where does the difference exist in organic and biochemistry branches of Chemistry?

The main difference between organic chemistry and biochemistry is that organic chemistry studies all types of organic compounds, while biochemistry only focuses on those compounds that are found in living organisms.

Q4. Give the reason of brilliance shown by diamond. Can you improve it?

The brilliance of a diamond is due to its ability to bend light that enters it. By bending the light, it separates white light into different colors. A highly polished and well-cut diamond shows even better brilliance.

Q5. Explain the dissolution of sodium chloride in water.

When we dissolve sodium chloride in water, the water molecules surround the sodium and chloride ions, which causes the salt to dissolve.

Q6. Why do different compounds have different solubilities in water at a particular temperature?

This is because temperature affects the solubility of different compounds differently. Some solutes dissolve better at high temperature, some at low temperature and some are not affected by the temperature at all. Because of this variation, different compounds have different solubilities.

Q7. Why NaCl can not be crystallized from water just like KNO3?

KNO3 crystallizes from water because its solubility changes with temperature. On the other hand, the solubility of NaCl does not change much with the temperature. So, NaCl can not crystallize in the same way as KNO3.

Q8. Why is graphite slippery to touch? Which property of graphite enables it to be used as lubricant?

Graphite is made up of multiple stacked layers of carbon atoms held together by very weak bonds. When rubbed, these layers slide over each other, reducing friction. These loosely bound layers make graphite useful as a lubricant.

4. Descriptive Questions

Q1. Mention the name of the branch of Chemistry in which you will study each of the following topics.

(a) Rate of a reaction

Physical chemistry

(b) Digestion of food in human body

Biochemistry

(c) Properties of plasma

Physical chemistry

(d) Ecosystem

Environmental chemistry

(e) Reactions taking place during fireworks

Inorganic chemistry

(f) Measurement of the absorption of wavelength with the help of ultraviolet spectrometer

Analytical chemistry

Q2. What are allotropic forms? Explain the allotropic forms of carbon and sulphur. How does coal differ from diamond?

See lecture no. 4.

Difference between coal and diamond:

Coal is a mixture of carbon, organic compounds, and other impurities. In contrast, diamond is a pure form of carbon element in which carbon atoms are bonded together to make a macromolecule.

Q3. What are supercritical fluids. How are they different from ordinary liquids? 

Q4. Define solubility of a solute. How does the solubility of solutes change with the increase in temperature?

See Lecture no. 7

Q5. What types of movements are present in gaseous and liquid molecules?

Movement of particles in liquids:

In liquids, the particles are held together by moderate intermolecular force. These forces keeps liquid particles close together while giving them a freedom of movement. As a result, they can move randomly within a container while remaining loosely bound together. This specific type of movement of liquid particles gives liquid state its specific properties such as:

  1. No shape but definite volume
  2. Incompressibility

Movement of particles in gases:

Gases have very weak intermolecular forces. These intermolecular forces are so weak that they cannot keep the gas particles closer and they are spread wide apart. Because of this weak intermolecular force, gas particles are free to move wherever they want. Due to this random motion of gas particles, gases exhibit their specific properties such as:

  1. No definite shape and no definite volume
  2. High compressibility

Q6. Differentiate between the areas which are studied under inorganic and organic chemistry.

Organic Chemistry

Inorganic Chemistry

1. Organic chemistry only deals with organic compounds which include hydrocarbons and their derivatives.

1. Inorganic chemistry deals with all types of substances other than organic compounds.

2. Since the carbon atom is the main component of organic compounds, organic chemistry mainly focuses on studying the properties of carbon.

2. Since the carbon atom is the main component of organic compounds, organic chemistry mainly focuses on studying the properties of carbon.

3. A large number of organic compounds are found in living organisms, so organic chemistry is closely related to biochemistry.

3. A large number of organic compounds are found in living organisms, so organic chemistry is closely related to biochemistry.

4. All organic compounds contain covalent bonds; therefore, organic chemistry primarily studies covalent bonding.

4. All organic compounds contain covalent bonds; therefore, organic chemistry primarily studies covalent bonding.

5. Investigative Questions

Q1. Preparation of solutions leads to an important process in chemistry which enables us to purify a compound through crystallization. Describe a process in which potassium nitrate is purified by crystallizing it in water.

Crystallization is a process in which impurities are removed from a substance based on the differences in their solubilities.

KNO3 is a salt that is soluble in water at high temperatures but less soluble at low temperatures.

Crystallization is based on two principles:

  1. Different compounds have different solubilities in a solvent
  2. The solubilities of solutes vary with changes in temperature

An impure sample contains two types of impurities:

  1. Water-insoluble impurities (e.g., sand) that can be separated through simple filtration.
  2. Water-soluble impurities (e.g., NaCl) that remain dissolved even at low temperatures.

Crystallization Process:

The crystallization process involves the following steps:

  1. Dissolution of impure sample in boiling water
  2. Filtration to remove insoluble impurities
  3. Slow cooling of the remaining solution so that the solubility of KNO3 decreases
  4. Formation of KNO3 crystal
  5. Collection of these crystals
  6. Drying of crystals

Q2. Graphene is called a miracle material, and it is the material of the future. Which of its many properties makes it very useful in electronics?

Graphene is well-suited for high-tech applications in electronics due to the following properties:

  1. Graphene is one of the best electrical conductors, making it ideal for use in high-end devices.
  2. It is only one atom thick, allowing the creation of ultra thin sensors and electronics.
  3. It is almost transparent, making it suitable for touchscreen displays.
  4. It is 200 times stronger than steel yet extremely flexible, which makes it ideal for bendable devices like folding phones.
  5. It is also an excellent heat conductor helping prevent overheating in electronic devices.