NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations
NCERT Solutions Class 10 Science Chapter 1 is a useful study material prepared by subject matter experts which has answers to all NCERT Class 10 Science book questions and are designed to clarify all your doubts by explaining every answer in an interesting way. The language used in NCERT Solutions for Class 10 Science Chapter 1 can be understood easily by all the students
NCERT Solutions for Class 10 Science Chapter 1 – A Brief Overview
NCERT Class 10 Science Chapter 1 mainly talks about chemical equations and how to balance them. With this, the students can also learn how certain chemicals react with others to create a completely new chemical. What makes this chapter interesting is the fact that the chemical equations and examples given are relatable. It mostly covers equations about chemicals that students widely use in their day-to-day life. For instance, every day students witness different chemical reactions like ice freezing, wax melting, salt dissolving in water, a candle’s flame extinguishing when someone blows it, rusting of iron, etc. All these instances are actually two or more chemicals reacting with each other and resulting in a change in their original properties. These reactions are usually irreversible. NCERT for Class 10 Science Chapter 1 covers all these reactions in detail.
The NCERT book has practice questions at the end of Chapter 1 so that students can revise the concepts learned and apply them in deriving the answers. To help students solve the practice questions, Extramarks provides NCERT Solutions for Class 10 Science Chapter Here are the benefits of referring to the solutions:
- NCERT Solutions for Class 10 Science Chapter 1 are prepared by subject matter experts as per the latest CBSE guidelines.
- NCERT Solutions Class 10 Science Chapter 1 can be accessed in both offline & online modes.
- NCERT Solutions have simple language and answers are written in a step-by-step manner.
NCERT Solutions for Class 10 Science
Chemical Reactions
A chemical reaction is when one substance reacts with another substance to form a new compound chemical or substance. The substances that go through a chemical change in the reaction are called reactants whereas the new substance formed during the reaction is known as a product. This new product has completely different properties in comparison to the reactants. A chemical equation is demonstrated by symbols. These symbols are a shorthand form of chemical names. For example:
H2S + O2 → H2O + SO2
When hydrogen sulfide reacts with oxygen molecules, it becomes water & sulfur dioxide.
In case of any chemical reaction, either or all of the below-listed changes in properties can be observed:
- Change in the state
- Change in color
- Change in temperature
- Formation of gas
Types of Chemical Reactions
Depending on the type of above-stated changes that take place during a chemical reaction, they can be classified as:
Combination Reaction:
When there is a breaking and making of bonds between atoms, new substances are formed. This type of reaction is called a combination reaction.
H2 + Cl → 2HCl
Hydrogen reacts with chlorine to form hydrogen chloride compounds.
Decomposition Reaction:
A decomposition reaction is when a single reactant breaks down to form different substances. These substances can be two or more. Depending on the energy required for the decomposition reaction, it can be classified into:
– Thermal Decomposition:
In a typical thermal decomposition reaction, heat energy is used for decomposing the reactant.
CaCO3 + Energy → CaO + CO2
Calcium carbonate when subjected to heat turns into oxo calcium and carbon dioxide.
– Electrolysis:
Chemical reactions where electrical energy is used for the decomposition of the reactant is called electrolysis. For instance,
2NaCl → 2Na + Cl2
When electricity is passed through sodium chloride, in the presence of electric energy it decomposes into sodium and chloride.
– Photochemical Reaction:
Chemical reactions where light energy is used for breaking down the reactant is called photolysis or photochemical reaction. For instance,
2AgCI(s) →2Ag(s) +CI2(g)
Silver chloride when subjected to light energy in the form of sunlight decomposes into silver metal and chlorine gas.
Exothermic or Endothermic Reaction:
Certain chemical reactions either liberate heat or absorb heat during the process. Depending on that, such decomposition reactions can be classified into exothermic or endothermic reactions.
– Exothermic Reaction:
The type of chemical reaction in which the products are formed because of the liberation of heat is called exothermic or combustion reaction. When we breathe in oxygen and exhale carbon dioxide, it is called an exothermic reaction. Likewise, when vegetables and fruits compost, the reaction is called exothermic.
– Endothermic Reaction:
The reactions that occur because of the absorption of heat, light or electricity are called endothermic reactions. All endothermic reactions require some form of energy for breaking down of the reactants For instance, photosynthesis is a type of endothermic reaction that occurs due to the presence of sunlight.
6CO2 (aq) + 12H2O (l) → C6H12O6 + 6O2 + 6H2O
Displacement Reaction:
When in a chemical reaction, a less reactive element gets replaced by a more reactive element from its compound, it is called a displacement reaction. Displacement reaction is also of two types:
– Single Displacement Reaction:
In this type of chemical reaction, an element from the compound displaces another element from the same compound. For instance,
Mg + 2HCl → MgCl2 + H2
– Double Displacement Reaction:
The type of displacement reaction in which groups of atoms in the molecules of a reactant are equally reactive and displace each other is called a double displacement reaction. As in this reaction, a precipitate is also produced, double displacement reactions are alternatively called as precipitation reactions. For example,
2KBr + BaI2 → 2KI + BaBr2
Oxidation & Reduction Reactions Or Redox Reactions :
In this type of chemical reaction, oxygen is either added or removed from the substance. If during the reaction, the substance gains oxygen, it is said to be oxidised. Whereas if during the reaction, the substance loses oxygen, it is said to be a reduction reaction.
The substance that oxidises another substance is called the oxidising agent. While the substance that causes the other substance to lose oxygen is called the reduction agent.
In simpler words, when both oxidation and reduction occur simultaneously, such reactions are called oxidation & reduction reactions or redox reactions.
MnO2 (s) + 4HCl→ MnCl2 (aq) + Cl2 (g) + 2H2O
In the above-stated example, HCl oxidizes to Cl2. On the other hand, MnO2 reduces to MnCl2.
Corrosion
Have you ever seen some metals like iron get coated by reddish brown powder? This happens when the upper surface of iron comes in contact with air, water, and chemicals in the atmosphere which leads to its rusting. This process is known as Corrosion. Some other examples of corrosion are black and green coating on silver and copper, respectively. It is a redox reaction and can be prevented by painting, galvanizing or electroplating the iron surface.
Rancidity
When fats and oil are oxidized leading to a loss in their original taste or smell. This is called rancidity. For instance, extra virgin olive oil goes rancid with time or when heated above its boiling point. But rancidity can be easily prevented by:
- Keep items in airtight containers.
- For cooked items that are prone to rancidity, refrigerate them. Alternatively, you can also pack them in nitrogen gas.
- Avoid keeping rancidity-prone foods under direct sunlight.
- Add BHA or BHT in the items to avoid rancidity.
Related Questions
Write the balanced equation for the following chemical reactions.
- i) Hydrogen + Chlorine →→ Hydrogen chloride
Ans: The balanced equation for the given reaction is: H2(g)+Cl2(g)→2HCl(g)
(A balanced equation should have the same number of atoms on both the reactant and product side of the equation.)