Join / Login

>>Class 7
>>Chemistry
>>Physical and Chemical Changes
>> $Chemical Changes$

Chemical Changes

Revise with Concepts

What Is a Chemical Change and Examples

ExampleDefinitionsFormulaes

Learn with Videos

Q: Which of the following are chemical changes?\$(a)\$ Growth of a plant\$(b)\$ Rusting of Iron\$(c)\$ Mixing of iron fillings and sand\$(d)\$ Cooking of food\$(e)\$ Digestion of food\$(f)\$ Freezing of water\$(g)\$ Burning of a candle.

A chemical change is a change that brings a change in the chemical properties of matter and a new substance is formed.Examples of chemical changes from the given list of changes are:Rusting of iron, Cooking of food, Digestion of food, and Burning of a candle.

Q: Anaerobic bacteria digest animal waste and produce biogas(Process-A). The biogas is then burnt as fuel(Process-B). The following statements pertain to these changes. Choose the correct one.

\$\textbf{Concept:}\$ Physical Change: Properties like size, shape, state (solid, liquid, or gas), temperature, pressure, etc., are physical properties. Those changes in which only physical properties of a substance change are called physical changes. There is no change in chemical composition.Chemical Change: The change in which a new substance is formed and the chemical composition of a substance are changed is called a chemical change. A substance loses its identity in a chemical change and cannot get back into its original form.\$\textbf{Correct Option:}\$ C\$\textbf{Explanation for correct option:}\$ Change A and change B both are chemical changes. As both the reaction are irreversible and they lead to the formation of new substances. There is also a change in the chemical properties of the reactants in both processes A and B.Animal waste \$\xrightarrow[bacteria] { anaerobic } \$ Bio gas (\$CH_4\$) Bio gas \$\xrightarrow { burning } \quad { CO }_{ 2 }+ other \ substances.\$\$\textbf{Explanation for incorrect options:}\$ according to given explanation both processes A and B are chemical changes.Hence, correct option is C.

Q: Rusting of iron is a chemical change because:

A change in which one or more new substances are formed is known as chemical change.When the iron is exposed to air and moisture, rust formation takes place. Rust is nothing but iron oxide; a new substance formed out of the reaction. The colour of the surface of the iron also changes. Hence, rusting of iron is a chemical change.

Q: Which of the following change is not a chemical change?

The boiling of water is not a chemical change. If it boils for more time it changes to vapour state which is a physical change.Whereas boiling of egg, burning of paper and cloth involves both physical and chemical change. The burning of paper and cloth forms ash.

Q: Photosynthesis in plants is a ________ change.

Photosynthesis is the process through which plants convert light energy into chemical energy. Here is the chemical reaction involved: water and carbon dioxide combine to form glucose and oxygen. Since new chemical species are formed, photosynthesis is clearly a chemical change.

Q: Which of the following is not a physical change?

LPG is flammable hydrocarbon gases that react with oxygen to form new products such as carbon dioxide (\${ CO }_{ 2 }\$) and water (\${ H }_{ 2 }O\$). Therefore, the combustion of LPG is a chemical change.\$n{ C }_{ x }{ H }_{ y }+z{ O }_{ 2 }\longrightarrow a{ CO }_{ 2 } + b{ H }_{ 2 }O\$ Option D is correct.

Q: Which of the following is a chemical change:

When iron comes in contact with air and moisture it reacts with it and forms a brownish layer on its surface due to the formation of its oxides. This is called rusting of iron. It is a chemical change since the new substance is formed.Melting of ice, boiling of water, and tearing of paper are all physical changes.Hence the option \$C\$ is correct.

Q: When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

\$\textbf{Concept: }\$ When any substance or object undergo any change which changes its chemical composition or form new substance. This type of change is known as chemical change.When baking soda is mixed with lemon juice, Carbon dioxide\$(CO_2)\$ gas is released in form of bubbles. As chemical composition of substance is getting changed and also new product is formed after mixing. Thus it is a chemical change.

Q: When a magnesium ribbon burns in air, the ash formed is dissolved in water:

On burning magnesium in air magnesium oxide is formed, when it is dissolved in water, a basic solution containing magnesium hydroxide is formed.

Q: What is a chemical change? Explain with example.

The changes in which new substance with new chemical properties are formed are called chemical changes.Example: Reaction between washing soda and lemon juice in which \$CO_2\$ and other substances are formed.

Chemical Change

5 mins

Quick Summary With Stories

Chemical Change

3 mins read

Important Questions

Which of the following are chemical changes?
$(a)$ Growth of a plant
$(b)$ Rusting of Iron
$(c)$ Mixing of iron fillings and sand
$(d)$ Cooking of food
$(e)$ Digestion of food
$(f)$ Freezing of water
$(g)$ Burning of a candle.

Medium

View solution

Anaerobic bacteria digest animal waste and produce biogas(Process-A). The biogas is then burnt as fuel(Process-B). The following statements pertain to these changes. Choose the correct one.

Medium

View solution

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

Medium

View solution

When a magnesium ribbon burns in air, the ash formed is dissolved in water:

Medium

View solution

What is a chemical change? Explain with example.

Medium

View solution

Revise with Concepts

What Is a Chemical Change and Examples

Learn with Videos

Quick Summary With Stories

Chemical Change

Which of the following are chemical changes? (a) Growth of a plant (b) Rusting of Iron (c) Mixing of iron fillings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of a candle.

Anaerobic bacteria digest animal waste and produce biogas(Process-A). The biogas is then burnt as fuel(Process-B). The following statements pertain to these changes. Choose the correct one.

Rusting of iron is a chemical change because:

Which of the following change is not a chemical change?

Photosynthesis in plants is a ________ change.

Which of the following is not a physical change?

Which of the following is a chemical change:

When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.

When a magnesium ribbon burns in air, the ash formed is dissolved in water:

What is a chemical change? Explain with example.

Which of the following are chemical changes?
$(a)$ Growth of a plant
$(b)$ Rusting of Iron
$(c)$ Mixing of iron fillings and sand
$(d)$ Cooking of food
$(e)$ Digestion of food
$(f)$ Freezing of water
$(g)$ Burning of a candle.