9.5.1 Introduction to Energetics

This is the first lecture from Chapter 5: “Energetics” in the new Class 9 Chemistry book (Punjab Board – PCTB). It briefly discusses the introduction of energetics and its related concepts. The lecture also includes a multiple-choice quiz and short question notes.

MCQs Based Quiz

1 / 18

What are the two main forms of energy studied in chemical energetics?

Kinetic and potential

Chemical and heat

Electrical and nuclear

Solar and thermal

2 / 18

The type of energy that is stored inside chemical bonds is called:

Kinetic energy

Electrical energy

Chemical energy

Heat Energy

3 / 18

The type of energy that is released when a bond is formed is called:

Kinetic energy

Electrical energy

Chemical energy

Heat Energy

4 / 18

The type of energy that is absorbed when a bond is broken is called:

Kinetic energy

Electrical energy

Chemical energy

Heat Energy

5 / 18

Which of the following is studied in energetics?

Mass exchange

Energy exchange

Electron exchange

All of these

6 / 18

A chemical reaction which involves the evolution of heat is called:

Irreversible reaction

Reversible reaction

Exothermic reaction

Endothermic reaction

7 / 18

A chemical reaction which involves the absorption of heat is called:

Irreversible reaction

Reversible reaction

Exothermic reaction

Endothermic reaction

8 / 18

In energetics, we study the chemical change that take place during ___.

A physical change

A chemical reaction

Nuclear reactions

Radioactivity

9 / 18

What is meant by enthalpy (H) of a compound?

Number of atoms in a compound

Chemical bonding in a compound

Types of atoms in a compound

Total thermal energy of a compound

10 / 18

The unit of enthalpy is:

$\mathrm{gmol^{-1}}$

$\mathrm{gcm^{-3}}$

$\mathrm{kJmol^{-1}}$

$\mathrm{molcm^{-3}}$

11 / 18

When the energy is absorbed during a chemical reaction, the total enthalpy of the system:

Increases

Decreases

Remains constant

Becomes zero

12 / 18

When the energy is released (evolved) during a chemical reaction, the total enthalpy of the system:

Increases

Decreases

Remains constant

Becomes zero

13 / 18

Chemical energetics is part of which field of chemistry?

Nuclear chemistry

Biochemistry

Thermodynamics

Analytical chemistry

14 / 18

Which of the following is studied in energetics?

Exchange of electrons in a reaction

Flow of energy in a reaction

Types of solvent required for a reaction

Types of apparatus required for a reaction

15 / 18

Who was the first person to use term ‘energy’ in the field of physics in 1802?

Thomas Young

Issac Newton

Amedeo Avogadro

E. Goldstein

16 / 18

Which of the following is studied in thermodynamics?

Energy changes during a reaction

Affect of energy changes on the properties of a system

Heat content of a system

All of these

17 / 18

When is heat energy released during a chemical reaction?

When bonds break

When bonds form

During phase changes

Only in gaseous reactions

18 / 18

When is heat energy absorbed during a chemical reaction?

When bonds break

When bonds form

During phase changes

Only in gaseous reactions

Your score is

The average score is 0%

Short Questions

Q1. What is energetics?

The branch of chemistry that studies the energy changes that take place during a chemical reaction is called energetics. These changes are caused by making and breaking of bonds.

Q2. What forms of energy are mainly studied in chemical energetics?

In chemical energetics, mainly two forms of energy are studied:

Chemical Energy: The energy stored between two atoms due to chemical bonding.
Heat Energy: The energy released when a bond is formed and absorbed when it is broken.

Q3. What is the definition of chemical energy?

The type of energy stored between a chemical bond formed between two atoms is called chemical energy.

Q4. How would you define heat energy using the concepts of chemical bonding?

The type of energy that is released when a bond is formed and absorbed when it is broken is called heat energy.

Q5. How does chemical bonding leads to the exchange of energy during a chemical reaction?

In chemical reactions, bonds of reactants break and new bonds in products are formed. Energy is needed to break a bond and released when a bond breaks. Therefore, chemical reactions always involve an exchange of energy.

Q6. How would you classify chemical reactions based on the exchange of energy (heat)?

Chemical reaction which involves the release (evolution) of energy (heat) is called an exothermic reaction. But if energy (heat) is absorbed during a chemical reaction it will be called an endothermic reaction.

Q7. Write the definition of endothermic reaction?

A type of reaction that involves the absorption of energy (heat) is called an endothermic reaction.

Q8. Write the definition of exothermic reaction?

A type of reaction that involves the release (evolution) of energy (heat) is called an endothermic reaction.

Q9. How would you define the enthalpy?

The total amount of thermal energy stored in a substance is called enthalpy (H) or heat content. Its unit is kJ mol^-1.

Q10. How would you define the heat content of a substance?

The total amount of thermal energy stored in a substance is called heat content or enthalpy (H). Its unit is kJ mol^-1.

Q11. How would enthalpy of a system change after the exchange of energy?

If energy is absorbed during a chemical reaction, the total enthalpy of the system increases. However, if energy is released (evolved), the total enthalpy of the system decreases.

Q12. What do you mean by thermodynamics?

It is a branch of science that deals with the energy changes during chemical reactions and how these changes affect the properties of a chemical system.

Q13. What is the role of Thomas Young in the field of physics?

He was the first person to use the term ‘energy’ in the field of physics.