Chemical Changes are also known as chemical reactions. The word “Chemical Change” is made of 2 words i.e. chemical and change. Chemical refers to the composition and properties of matter at the atomic and molecular level, while change tells us about transformation. Most of the chemical changes occur in a natural environment, like evaporation, condensation, rainfall, and so on. All of these changes imply a state change.
In this article, we will explore the concept of chemical change in detail including its definition, types, and factors affecting the changes as well as some examples.
What is a Chemical Change?
Chemical change refers to a process in which one or more substances are converted into new substances with different chemical compositions and properties.
During a chemical change, the bonds between the atoms are broken down to form a new molecule. This transformation is accompanied by a change in energy, often in the release or absorption of heat, light, or sound.
Unlike physical changes, which do not alter the fundamental composition of a substance, chemical changes result in the creation of distinct products with unique chemical identities.
Read More about Chemical Reaction.
Chemical Change Definition
The process in which one or more substances change results in the formation of new substances with different chemical compositions and properties.
Chemical Changes Example
There are thousands of chemical reactions. These changes are easy to understand and are related to our day-to-day life. Let us understand some of them.
- Rusting of Iron: When iron is made to react with oxygen and water, it forms iron oxide i.e. rust. This is a chemical change because the composition of the iron is altered.
- Combustion: Burning a piece of paper, wood, or any fuel is a chemical change.
- Digestion: In the human body, the process of digestion involves the breakdown of food into simpler chemical compounds through enzymatic reactions, resulting in the absorption of nutrients by the body.
- Photosynthesis: During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen using energy from sunlight.
- Oxidation of Food: When fruits or vegetables are cut and exposed to air, they undergo oxidation, leading to browning (e.g., when an apple turns brown after being sliced).
Read More about Rusting of Iron.
Chemical Change in Everyday Life
Chemical changes are also a part of our daily lives. They occur during various natural processes and human activities such as digestion and respiration.
- Cooking and Baking: Cooking and baking can be seen as chemical reactions as both involve the transformation of ingredients through various chemical reactions.
- For example, in cooking, the Maillard reaction occurs when amino acids and reducing sugars in food break down and form new flavorful compounds. Similarly, in baking, chemical leavening agents like baking powder or baking soda undergo a reaction with moisture and heat to release carbon dioxide gas, causing the dough or batter to rise.
- Digestion and Metabolism: Digestion and metabolism are complex processes that involve various chemical reactions in the body.
- Digestion is the process of breaking down food into smaller molecules that can be absorbed and utilized by the body. Metabolism, on the other hand, is the overall process of breaking down and utilizing energy from food, water, and other nutrients.
Chemical Change in Nature
Some of the common chemical changes in nature are:
- Photosynthesis: Photosynthesis is a natural process in plants, algae, and some bacteria that use sunlight, water, and carbon dioxide to make their food and its main output is glucose.
- Decay and Decomposition: Decay and decomposition are chemical processes that break matter into simpler compounds. To occur, this process typically requires the presence of an oxidizing agent or an infection. It could also involve the influence of enzymes, light, heat or other external factors.
Signs of Chemical Change
There are several key evidences that indicate a chemical change has taken place, some of these evidences are:
- Color Change: Observable transformation of starting materials, e.g., iron rusting from silver-grey to reddish-brown.
- Production of an Odor: Release of new substances with distinct odors not present in the starting materials.
- Example: Mixing vinegar and baking soda produces carbon dioxide gas with a slightly sour odor.
- Change in Temperature:
- Exothermic reactions release energy, leading to a temperature increase.
- Endothermic reactions absorb energy, causing a temperature decrease.
- Example: Lighting a match results in an exothermic combustion reaction, raising the temperature significantly.
- Evolution of a Gas (Formation of Bubbles): Production of gas bubbles as a new product.
- Observable in reactions like acid with metal or baking soda decomposition.
- Formation of a Precipitate: Solid formation when two solutions are mixed, resulting in an insoluble product.
- Example: Mixing silver nitrate solution with sodium chloride solution forms a white precipitate of silver chloride.
Additional Signs of Chemical Change
Some other signs are:
- Change in Luminosity (Light Emission): Some reactions, like combustion or bioluminescence, release energy in the form of light.
- Change in Sound: Some reactions produce sound, such as the hissing of escaping gas or the popping sound of a burning firework.
- Change in Taste: Chemical reactions can alter the taste of substances.
- Example: Mixing baking soda with vinegar results in a solution tasting salty due to the formation of sodium chloride.
Types of Chemical Change
There are different types of chemical change for which there are various reactions as well. These reactions are:
- Combustion Reaction
- Acid-Base Reactions
- Oxidation-Reduction (Redox) Reactions
- Precipitation Reactions
- Synthesis Reactions
- Decomposition Reactions
- Photosynthesis and Respiration
Factors Affecting Chemical Changes
There are different types of factors that affect the rate of chemical reactions. Some of the factors affecting chemical reactions are:
Temperature
Chemical Reactions are directly proportional to temperature i.e. when the temperature is high the rate of chemical reaction is high. When the temperature is low the rate of chemical reaction is low.
Concentration
The concentration of reactants in a solution affects reaction rates. Higher concentrations typically lead to faster reactions because there are more reactant molecules or ions available to collide and interact with each other. The rate of reaction is directly proportional to the concentration of reactants.
Pressure
Chemical Reactions are directly proportional to Pressure i.e. when the pressure is high the rate of chemical reaction is high and when the pressure is low the rate of chemical reaction is low.
Catalysts
Catalysts 5 are nothing but substances that can accelerate the rate of reaction. When the catalysts are added into a reaction then the rate of reaction is increased i.e. the chemical reaction becomes fast.
Surface Area
In reactions involving solid reactants, the surface area of the solids can impact the rate of reaction. Finely powdered or granulated solids have a greater surface area compared to large chunks, allowing for more contact with other reactants and thus faster reactions.
Difference between Physical and Chemical Change
A physical change is a change in the state or appearance of a substance, but its chemical composition remains the same such as melting, boiling, or evaporation. On the other hand, a chemical change involves a change in the chemical composition of a substance.
Read more about Physical and Chemical Change.
Chemical Change Vs Physical Change
The key difference between chemical and physical change are listed in the following table:
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A change that results in the formation of new substances with different chemical properties.
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A change in the physical properties of a substance without a change in its chemical composition.
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Alters the chemical composition of the substances involved.
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Does not alter the chemical composition of the substances involved.
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It is difficult or impossible to reverse the change.
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Usually reversible; the original substance can often be obtained again.
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It often involves the release or absorption of energy, such as heat or light.
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Typically involves energy changes but does not involve the formation or breaking of chemical bonds.
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Combustion, rusting, cooking an egg, digestion, and baking.
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Melting, freezing, boiling, cutting, dissolving, and crushing.
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Involves the rearrangement of atoms and molecules.
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Involves a rearrangement of particles, but the same atoms and molecules remain.
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May produce a color change, gas evolution, or formation of a precipitate.
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Usually does not result in significant changes in the appearance or chemical properties of the substances.
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Can be represented by chemical equations showing reactants and products.
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Typically not represented by chemical equations, but may be shown with phase changes.
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Read More,
Sample Questions on Chemical Change
Following are some of the commonly asked questions on Chemical Change:
1. Explain Chemical Change.
Chemical change refers to a process in which one or more substances are converted into new substances with different chemical compositions and properties.
2. Is Boiling a Chemical Change?
Boiling is a physical change, not a chemical change. In boiling, a substance changes its state from a liquid to a gas due to the absorption of heat energy. The chemical composition of the substance remains unchanged.
3. Is Sugar Dissolving in Water a Chemical Change?
No, the dissolving of sugar in water is a physical change, not a chemical change. It involves the breaking of intermolecular forces between sugar molecules, allowing them to mix with water. The chemical composition of sugar remains unchanged.
4. Is the Burning of a Candle a Chemical Change?
Yes, Burning a candle is a chemical change, When you light a candle, the wax melts and releases a mixture of carbon dioxide (CO2), water vapor (H2O), and other chemicals into the air.Â
5. Is baking a cake a Chemical Change?
Baking a cake is a chemical change because it involves the transformation of ingredients into a new substance with different physical and chemical properties. This process involves the mixing of flour, sugar, eggs, and other ingredients causing chemical reactions such as the formation of gluten and the production of carbon dioxide gas.
6. Is ripening fruit a Chemical Change?
Fruit ripening is a chemical process. The pigment in the skin of the fruit changes throughout ripening and cannot be reverted.
7. Is frying an egg a Chemical Change?
No, frying an egg does not result in a chemical change in the egg. The yolk and white will still be the same proteins and fats they were before cooking.
8. Is the burning of a candle a Chemical Change?
The burning of a candle is a chemical change as it involves a process called combustion, which is a type of chemical reaction that releases heat and light.
9. Which of the following is not a Chemical Change?
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Freezing of Water
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Photosynthesis
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Combustion
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Rusting of Iron
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Correct option is ‘a’ as when water freezes, its atoms rearrange themselves into a crystalline structure, but the chemical composition of the water molecules remains the same.
FAQs on Chemical changes
1. What are Chemical Reactions?
Chemical reactions are nothing but the process in which two or more substances undergo changes that result in the formation of a new substance.
2. How are Chemical Changes different from Physical Changes?
Chemical changes involve a change in the chemical composition of substances, resulting in the formation of new substances. In contrast, physical changes alter the physical state or appearance of a substance without changing its chemical composition.
3. How can you Recognize a Chemical Change?
Signs of a chemical change include the production of heat or light, the formation of a gas or a solid precipitate, a change in color, and the release or absorption of energy.
4. What Factors influence the Rate of Chemical Reactions?
Factors influencing the rate of chemical reactions are:
- Temperature
- Concentration
- Pressure
- Catalysts
5. What are some Common Examples of Chemical Changes?
Common examples of chemical changes include the rusting of iron, combustion (burning of fuels), cooking food, fermentation, melting of ice chemical change and the digestion of food in the human body.
6. Is Digestion of food a Chemical Change?
Yes, the digestion of food is a chemical change. In the process of digestion, food molecules are broken down into smaller compounds by enzymes and other chemical reactions in the body.
7. Is Burning Wood a Chemical Change?
The burning of wood is a chemical change as it leads to the formation of new substances like Carbon dioxide gas, water vapour, ash, etc.
8. Is Sour Milk a Chemical Change?
The souring of milk is classified as a chemical change because it results in the production of sour-tasting lactic acid.
9. Is Photosynthesis a Chemical Change?
Photosynthesis is a chemical change as new products such as energy, carbon dioxide and water are produced.
10. Is Freezing Water a Chemical Change?
Freezing water is a physical change, not a chemical change. When water freezes, its atoms rearrange themselves into a crystalline structure, but the chemical composition of the water molecules remains the same.
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