Class 9 chemistry is part of the class 9 science syllabus. The chemistry portion of the class 9 science syllabus includes the following chapters, Matter in Our Surroundings, Is Matter Pure Around us, Atoms and Molecules, and Structure of Atom. Four chapters comprise the class chemistry syllabus. One of the most important chapters of class 9 chemistry is Is Matter Around Us

Examples

Question 1

What is a physical change?

Solution 1

A physical change is a temporary change in which no new substance is formed and the composition or identity of the substance is not altered although certain specific physical properties may be changed.

Question 2

What is a   chemical change?

Solution 2

A chemical change is a permanent change in which the original substance gives rise to one or more substances with different properties.

Question 3

Indicate which of the following statements are true and which are false.

(a) A change, whether physical or chemical is always permanent.

(b) Photosynthesis in plants is a physical change.

(c) The mass of a substance does not change on burning.

(d) Carbohydrates burn in air to give carbon and water.

(e) A chemical change is always accompanied by the evolution or absorption of heat.

Solution 3

(a) False

(b) False

(c) False

(d) False

(e) True

Question 4 

What is the difference between physical and chemical changes?

Solution 4: 

Differences Between Physical and Chemical Change

Question 5: Which of the following is a chemical change? (a) Growth of a plant (b) Rusting of iron (c) Mixing of iron filings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of a candle.

Solution 5: 

If the chemical composition is changing, then it is a chemical change, and if the chemical composition is remaining the same, then it is a physical change.

Growth of a plant, rusting of iron, cooking of food, digestion of food, and burning the candle are chemical changes because here is the chemical composition of the substance changes.

Question 6: Which of the following is not a chemical change? a) Formation of curd b) ripening of banana c) corrosion of iron d) melting of wax​

Solution 6:  Melting of wax is not a chemical change.

Option (d).

Explanation:

• Mainly there are two types of changes which are chemical and Physical.
• Such changes in which a new substance is formed from a substance and which can’t be reversed are known as the Chemical changes.
• Among the given options Formation of Curd,  Ripening of banana and Corrosion of iron are examples of a chemical reaction as each of these changes can not be reversed, whereas melting of wax is a physical change as in this there is only change in the physical state , no new substance is formed.

Practice Questions

1. What is the difference between physical and chemical changes?
   
   
2. Which of the following is a chemical change? A. Boiling of water B. Boiling of egg C. Burning of paper D. Burning of cloth
   
   
3. Which of the following is a chemical change?

1. growth of a plant
2. rusting of iron
3. mixing of iron filings and sand
4. cooking of food
5. digestion of food
6. freezing of water
7. burning of a candle
   
   

1. The property of flow is unique to fluids. Which one of the following statements is correct?

(a) Only gases behave like fluids

(b) Gases and solids behave like fluids

(c) Gases and liquids behave like fluids

(d) Only liquids are fluids

1. The boiling point of water at sea level is
   1. 0°C
   2. 273 K
   3. 373 K
   4. 273°C
      
      
2. Which of the following is not a chemical change? 

1. Burning of fuels
2. Rusting of Iron
3. Drying of clothes
4. Formation of curd from milk
   
   

1. At room temperature the forces of attraction between the particles of solid substances are ………….. than those which exist in the gaseous state.
   
   
2. Which of the following is not a chemical change?

(A) Sublimation

(B) Combustion

(C) Electrolysis

(D) Rusting

8. Give some chemical change examples. 

Pure? In this chapter, we learn about many things, including the difference between physical and chemical changes.

Study Material

1. Difference Between Physical And Chemical Change
   
   We encounter a lot of changes in our surroundings day to day that which we may not necessarily notice. For instance, melting of wax, rusting of iron, bread turning into toast and more. All of these changes are physical changes or chemical changes. Thus, in this article, we will study the difference between physical and chemical change. Physical change is when the physical traits of a substance changes. Moreover, it does not make any internal changes. Whereas, a chemical change is when the internal structure gets affected by a substance and forms a new substance.
   
   Changes in energy are always accompanied by a particular chemical change or physical change.  Many changes happen in a natural environment such as evaporation of water, condensation, rainfall, etc. The change in state is involved in all these changes. During some reaction, the old bonds in the reactants break and new bonds are created in the products.

2. What is Chemical Change?
   
   

• The change in which the molecular composition is completely altered and a new product is formed is called a chemical change.
• Chemical changes create a new product.
• Chemical changes are irreversible and permanent.
• It reveals that chemical change cannot be reversed by changing or altering the experimental changes.
• The mass of the substance is altered during a chemical change. Either the mass is added or removed.
• During a chemical change, the energy changes occur. There is an energy difference in the breaking of old bonds in reactants and the formation of new bonds in products.
• The reaction is called an exothermic reaction if the energy is released and as an endothermic reaction when the energy is absorbed.

Examples of Chemical Change

1. Burning of wood or paper
2. Burning of camphor
3. Souring of milk
4. Burning of candle
5. Digestion of food

There is a difference in energy during the breaking and making of bonds. The energy is given out to the surroundings if the energy required to break the bonds is higher than the energy required to make the bonds.

These changes or reactions are called exothermic. But, the energy is absorbed from the environment when the energy needed to break the bond is lower than the energy required to make the bonds. Such reactions are called endothermic reactions.

3. What is Physical Change?

• During physical change, the arrangement of molecules is altered leading to change in state. No new products are formed, and the molecular composition remains totally the same.  For example, the molecular composition of ice and water is not altered.
• No energy changes occur when as a result of a physical change. The energy needed to bring a physical change is equal to the amount of energy required to reverse the change. There is no change in energy.
• The changes are reversible and temporary. The reaction gets reversed if the cause of producing the change is removed. For example, water on freezing forms ice and ice on melting forms water.
• During the physical change, the mass of the substance remains the same. Only energy is added or removed, and mass is not involved in a physical change.

Examples of Physical Change

1. Dissolution of sugar in water
2. Melting of ice
3. Freezing of water
4. Boiling of water
5. Melting of wax

Difference between physical and chemical change:

There are many differences between physical and chemical changes and it is important to understand them to be able to understand these concepts clearly. The comparison and difference between physical and chemical changes are given below along with their examples.