Class 10 Science Chapter 1 In Hindi Medium Pdf Download
Harriet Wehrenberg
Class 10 Science Chapter 1 in Hindi Medium PDF Download
Class 10 Science Chapter 1 is one of the most important chapters in the CBSE syllabus. It deals with the topic of chemical reactions and equations, which are the basis of chemistry and many other fields of science. In this chapter, you will learn about the different types of chemical reactions, their characteristics, and how to write and balance chemical equations. You will also learn about the effects of unbalanced chemical equations on the environment and human health.
If you are looking for a PDF download of this chapter in Hindi medium, you have come to the right place. In this article, we will provide you with a link to download the NCERT book for Class 10 Science Chapter 1 in Hindi medium for free. You can also access other useful resources such as NCERT solutions, notes, important questions, MCQs, etc. from our website.
To download the PDF of Class 10 Science Chapter 1 in Hindi medium, click on the link below:
Chemical Reactions and Equations
Definition and examples of chemical reactions
A chemical reaction is a process in which one or more substances (called reactants) are changed into one or more new substances (called products). The atoms of the reactants are rearranged in a chemical reaction, resulting in the formation of different substances with different properties.
For example, when magnesium ribbon is burnt in air, it reacts with oxygen to form magnesium oxide, which is a white ash. This is a chemical reaction because a new substance (magnesium oxide) is formed from the original substances (magnesium and oxygen).
Another example of a chemical reaction is the rusting of iron. When iron is exposed to moist air, it reacts with oxygen and water to form iron oxide, which is a brown substance. This is also a chemical reaction because a new substance (iron oxide) is formed from the original substances (iron, oxygen, and water).
Types of chemical reactions
There are many types of chemical reactions, but some of the common ones are:
Combination reactions
A combination reaction is a type of chemical reaction in which two or more substances combine to form a single substance. The general form of a combination reaction is:
A + B AB
For example, when hydrogen gas and chlorine gas are mixed, they combine to form hydrogen chloride gas.
H2(g) + Cl2(g) 2HCl(g)
Decomposition reactions
A decomposition reaction is a type of chemical reaction in which a single substance breaks down into two or more simpler substances. The general form of a decomposition reaction is:
AB A + B
For example, when calcium carbonate (limestone) is heated strongly, it decomposes into calcium oxide (quicklime) and carbon dioxide gas.
CaCO3(s) CaO(s) + CO2(g)
Displacement reactions
A displacement reaction is a type of chemical reaction in which a more reactive element displaces a less reactive element from its compound. The general form of a displacement reaction is:
A + BC AC + B
For example, when zinc metal is added to copper sulphate solution, zinc displaces copper from its compound and forms zinc sulphate solution and copper metal.
Zn(s) + CuSO4(aq) ZnSO4(aq) + Cu(s)
Double displacement reactions
A double displacement reaction is a type of chemical reaction in which two compounds exchange their ions to form two new compounds. The general form of a double displacement reaction is:
AB + CD AD + CB
For example, when sodium sulphate solution and barium chloride solution are mixed, they exchange their ions and form barium sulphate precipitate and sodium chloride solution.
Na2SO4(aq) + BaCl2(aq) BaSO4(s) + 2NaCl(aq)
Oxidation and reduction reactions
An oxidation and reduction reaction is a type of chemical reaction in which one substance loses electrons (oxidation) and another substance gains electrons (reduction). The substance that loses electrons is called the reducing agent, and the substance that gains electrons is called the oxidizing agent. The general form of an oxidation and reduction reaction is:
A + B A + B
For example, when copper oxide is heated with hydrogen gas, copper oxide loses oxygen (oxidation) and hydrogen gas gains oxygen (reduction). Copper oxide is the oxidizing agent and hydrogen gas is the reducing agent.
CuO(s) + H2(g) Cu(s) + H2O(g)
Characteristics of chemical reactions
Chemical reactions are accompanied by some observable changes that indicate that a new substance has been formed. Some of the common characteristics of chemical reactions are:
Evolution of gas
Sometimes, a chemical reaction produces a gas as one of the products. The gas can be seen as bubbles or fumes coming out of the reaction mixture. For example, when vinegar (acetic acid) is added to baking soda (sodium bicarbonate), carbon dioxide gas is evolved.
CH3COOH(aq) + NaHCO3(s) CH3COONa(aq) + H2O(l) + CO2(g)
Change in temperature
Sometimes, a chemical reaction releases or absorbs heat energy from the surroundings. This causes a change in the temperature of the reaction mixture. For example, when magnesium ribbon is burnt in air, heat energy is released and the temperature of the reaction mixture increases.
Mg(s) + O2(g) 2MgO(s) + Heat energy
Formation of precipitate
Sometimes, a chemical reaction produces an insoluble solid as one of the products. The solid settles down at the bottom of the reaction vessel or remains suspended in the liquid. This solid is called a precipitate. For example, when lead nitrate solution and potassium iodide solution are mixed, a yellow precipitate of lead iodide is formed.
Pb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)
Change in colour
Sometimes, a chemical reaction produces a product that has a different colour from the reactants. This causes a change in the colour of the reaction mixture. For example, when iron nails are dipped in copper sulphate solution, iron displaces copper from its compound and forms iron sulphate solution, which is green in colour. The colour of the solution changes from blue to green.
CuSO4(aq) + Fe(s) Fe SO4(aq) + Cu(s)
Change of state
Sometimes, a chemical reaction produces a product that has a different state (solid, liquid, or gas) from the reactants. This causes a change in the state of the reaction mixture. For example, when water is electrolysed, it decomposes into hydrogen gas and oxygen gas.
2H2O(l) 2H2(g) + O2(g)
Chemical equations
Definition and symbols of chemical equations
A chemical equation is a way of representing a chemical reaction using the symbols and formulas of the reactants and products. It shows the number and type of atoms involved in the reaction, as well as the physical state and conditions of the reaction.
A chemical equation consists of two parts: the left-hand side (LHS) and the right-hand side (RHS). The LHS shows the reactants and the RHS shows the products. An arrow () is used to separate the LHS and the RHS, and indicates the direction of the reaction.
Some common symbols and abbreviations used in chemical equations are:
| Symbol | Meaning |
|---|
| (s) | Solid state |
| (l) | Liquid state |
| (g) | Gaseous state |
| (aq) | Aqueous state (dissolved in water) |
| + | Plus sign (used to separate two or more reactants or products) |
| Yields or produces (used to separate reactants and products) |
| Reversible reaction (used to indicate that the reaction can proceed in both directions) |
| Δ | Heat (used to indicate that heat is supplied to the reaction) |
| Catalyst (used to indicate that a substance is added to speed up the reaction without being consumed) |
| [ ] | Concentration (used to indicate the concentration of a substance in moles per litre) |
| Pressure (used to indicate the pressure of a substance in atmospheres) |
| ( ) | Temperature (used to indicate the temperature of a substance in degrees Celsius) |
Balancing of chemical equations
Balancing of chemical equations is a process of ensuring that the number and type of atoms on both sides of the equation are equal. This is based on the law of conservation of mass, which states that matter can neither be created nor destroyed in a chemical reaction.
To balance a chemical equation, we need to adjust the coefficients (the numbers before the symbols or formulas) of the reactants and products, so that they have the same number of atoms of each element. We cannot change the subscripts (the numbers after the symbols) of the reactants and products, as they indicate their chemical formulas.
For example, consider the following unbalanced chemical equation:
Zn + HCl ZnCl2 + H2
To balance this equation, we need to make sure that there are equal numbers of zinc, hydrogen, and chlorine atoms on both sides. We can do this by placing a 2 before HCl on the LHS and before H2 on the RHS. This gives us:
Zn + 2HCl ZnCl2 + 2H2
This equation is now balanced, as there are one zinc atom, two hydrogen atoms, and two chlorine atoms on both sides.
Effects of unbalanced chemical equations
If a chemical equation is not balanced, it means that it does not follow the law of conservation of mass. This implies that some atoms are either created or destroyed in the reaction, which is not possible. Therefore, an unbalanced chemical equation does not accurately represent a chemical reaction.
An unbalanced chemical equation can also lead to incorrect calculations and predictions about the quantities and properties of the reactants and products. For example, if we use an unbalanced chemical equation to calculate the mass of a product, we may get a wrong answer that violates the law of conservation of mass. For example, if we use the unbalanced equation:
Zn + HCl ZnCl2 + H2
65 g Zn (1 mol Zn / 65 g Zn) (1 mol H2 / 1 mol Zn) (2 g H2 / 1 mol H2) = 2 g H2
73 g HCl (1 mol HCl / 36.5 g HCl) (1 mol H2 / 1 mol HCl) (2 g H2 / 1 mol H2) = 4 g H2
Total mass of H2 = 2 g + 4 g = 6 g
This answer is incorrect, as it implies that the mass of the products (ZnCl2 + H2) is more than the mass of the reactants (Zn + HCl). This violates the law of conservation of mass, which states that the mass of the products must be equal to the mass of the reactants.
If we use the balanced equation:
Zn + 2HCl ZnCl2 + 2H2
65 g Zn (1 mol Zn / 65 g Zn) (1 mol H2 / 1 mol Zn) (2 g H2 / 1 mol H2) = 2 g H2
73 g HCl (1 mol HCl / 36.5 g HCl) (1 mol H2 / 2 mol HCl) (2 g H2 / 1 mol H2) = 2 g H2
Total mass of H2 = 2 g + 2 g = 4 g
This answer is correct, as it implies that the mass of the products (ZnCl2 + H2) is equal to the mass of the reactants (Zn + HCl). This follows the law of conservation of mass, which states that the mass of the products must be equal to the mass of the reactants.
Summary and Key Points
In this article, we have learned about Class 10 Science Chapter 1 in Hindi medium PDF download. We have also learned about the following concepts and terms related to chemical reactions and equations:
- A chemical reaction is a process in which one or more substances are changed into one or more new substances.
- A chemical equation is a way of representing a chemical reaction using the symbols and formulas of the reactants and products.
- A balanced chemical equation is a chemical equation that follows the law of conservation of mass, which states that matter can neither be created nor destroyed in a chemical reaction.
- An unbalanced chemical equation is a chemical equation that does not follow the law of conservation of mass, and may lead to incorrect calculations and predictions.
- The common types of chemical reactions are combination reactions, decomposition reactions, displacement reactions, double displacement reactions, and oxidation and reduction reactions.
- The common characteristics of chemical reactions are evolution of gas, change in temperature, formation of precipitate, change in colour, and change of state.
Frequently Asked Questions and Answers
Q1. What is the difference between a physical change and a chemical change?
A1. A physical change is a change in which no new substance is formed and only the physical properties such as shape, size, colour, state, etc. are changed. For example, melting of ice, cutting of paper, bending of wire, etc. are physical changes.
Q2. What is the difference between an endothermic reaction and an exothermic reaction?
A2. An endothermic reaction is a type of chemical reaction in which heat energy is absorbed from the surroundings. The temperature of the reaction mixture decreases in an endothermic reaction. For example, photosynthesis, decomposition of calcium carbonate, etc. are endothermic reactions.
An exothermic reaction is a type of chemical reaction in which heat energy is released to the surroundings. The temperature of the reaction mixture increases in an exothermic reaction. For example, combustion, respiration, neutralization, etc. are exothermic reactions.
Q3. What is the difference between a catalyst and an inhibitor?
A3. A catalyst is a substance that speeds up the rate of a chemical reaction without being consumed or changed in the process. It lowers the activation energy required for the reaction to occur. For example, platinum, manganese dioxide, enzymes, etc. are catalysts.
An inhibitor is a substance that slows down the rate of a chemical reaction or prevents it from occurring. It increases the activation energy required for the reaction to occur. For example, preservatives, antioxidants, poisons, etc. are inhibitors.
Q4. What is the difference between oxidation and reduction?
A4. Oxidation is a process in which a substance loses electrons or gains oxygen or loses hydrogen. It results in an increase in the oxidation state or valency of the substance. For example, when iron rusts, it loses electrons and gains oxygen.
Fe(s) Fe(aq) + 2e (loss of electrons)
Fe(s) + O2(g) Fe2O3(s) (gain of oxygen)
Reduction is a process in which a substance gains electrons or loses oxygen or gains hydrogen. It results in a decrease in the oxidation state or valency of the substance. For example, when copper oxide is reduced by hydrogen gas, it gains electrons and loses oxygen.
Cu(aq) + 2e Cu(s) (gain of electrons)
CuO(s) + H2(g) Cu(s) + H2O(g) (loss of oxygen)
Q5. What is the difference between a skeleton equation and a balanced equation?
A5. A skeleton equation is a chemical equation that shows only the symbols and formulas of the reactants and products without indicating their coefficients or physical states. It does not follow the law of conservation of mass and may have unequal numbers of atoms on both sides. For example:
Zn + HCl ZnCl2 + H2 (skeleton equation)
A balanced equation is a chemical equation that shows the symbols and formulas of the reactants and products along with their coefficients and physical states. It follows the law of conservation of mass and has equal numbers of atoms on both sides. For example:
Zn(s) + 2HCl(aq) ZnCl2(aq) + 2H2(g) (balanced equation)