This PSEB 10th Class Science Notes Chapter 1 Chemical Reactions and Equations will help you in revision during exams.
PSEB 10th Class Science Notes Chapter 1 Chemical Reactions and Equations
→ In a chemical reaction, old bonds in the reactants are broken forming new bonds to give products.
→ A chemical equation represents a chemical reaction.
→ By using chemical formulae instead of words, chemical equations can be made more useful and concise.
→ According to the law of conservation of mass matter (or Mass) can neither be created nor destroyed in a chemical reaction.
→ If the number of atoms of each element is the same on both sides of the arrow in a chemical reaction then the chemical equation is a balanced equation.
→ The method used to balance chemical equations is known as the Hit-and-Trial method since we make trials to balance the equation by using the smallest whole number coefficient.
→ The solid, gas, liquid, and aqueous states of reactants and products are represented by the notations: (s), (g), (l), and (aq) respectively.
→ When reactants and products are present as solutions in water then the word aqueous (aq) is written.
→ When (g) is written with water, it means that water is present in the form of vapour.
→ A reaction in which two or more reactants combine to form a single product is known as a combination reaction.
→ The chemical formula for marble is CaCO3.
→ After two three days of whitewashing, calcium carbonate is formed which gives a shiny finish to the walls.
→ We get energy from food.
→ During digestion, food is broken into fine particles of simpler substances.
→ The decomposition of vegetable matter into compost is an example of an exothermic reaction.
→ A reaction in which a single reactant breaks down to give simpler products is called a decomposition reaction.
→ On heating, crystals of ferrous sulfate crystals lose water, and their color changes.
→ NO2 fumes are brown in colour.
→ The white colour of silver chloride changes into a grey colour in sunlight.
→ The chemical reactions in which energy is given out are called exothermic reactions.
→ Those reactions in which energy is absorbed are known as endothermic reactions.
→ Those reactions in which there is an exchange of ions between the reactants are called double displacement reactions.
→ Those reactions in which precipitates are formed are known as precipitate reactions.
→ If in a reaction one of the reactants gets oxidized and the other gets reduced, then such a reaction is called a redox reaction.
→ In a reaction, a substance is oxidized when there is a gain of O2 or a loss of H2 in it.
→ A substance is reduced when it gains H2 or loses O2.
→ When a metal comes in contact with acid or moisture around it, gets corroded and the process is called corrosion.
→ Examples of corrosion are black coating on silver and green coating on copper.
→ Oxidation of oils and fats become rancid and their taste and smell change.
→ To slow down the oxidation process of food materials these are kept in air-tight containers.
→ Chemical change: It is a reaction in which new substances are formed. It is called a chemical change.
→ Chemical reaction: A process in which chemical change takes place is called a chemical reaction.
→ Reactants: Those substances which take part in a chemical reaction are called reactants.
→ Products: Those substances which are formed in a chemical reaction are called products.
→ Combination reaction: It is a chemical reaction in which two or more two substances combine to form a single substance.
→ Decomposition reaction: It is a chemical reaction in which a molecule breaks into molecules of simpler substances.
→ Displacement reaction: A reaction in which a substance displaces another substance is called a displacement reaction.
→ Double displacement reaction: This is a reaction in which there is a mutual exchange between two different atoms or groups of atoms.
→ Neutral solution: When an acid and a base are mixed in a proper proportion, then we get a neutral solution.
→ Neutralisation reaction: When we get salt and water as the only products by mixing acid and base, then such a reaction is known as a Neutral reaction.
→ Oxidation: A substance is oxidized when there is a gain of oxygen or a loss of hydrogen in the substance.
→ Reduction: A substance is reduced when there is a loss of oxygen and a gain of hydrogen in the substance.
→ Redox reaction: A reaction in which oxidation and reduction both take place simultaneously is called a redox reaction.
→ Exothermic reaction: Those reactions in which heat is produced along with the products are called exothermic reactions.
→ Endothermic reactions: Those reactions in which heat is absorbed are called endothermic reactions.
→ Precipitation reactions: When two solutions are mixed and due to reaction between them a white coloured substance (or some other colour) is formed which is insoluble in water, then this is called a precipitation reaction.
→ Fermentation: The change of carbonic substances with the help of microorganisms or enzymes into simple carbonic substances is called fermentation.
→ Rancidity: When fat/oil-containing food materials are left for a long time then due to oxidation there is a change in their smell and taste, this change is called rancidity.
→ Reducing agent: That substance that gets oxidised itself or reduces the other substances by giving electrons is called a reducing agent.
→ Oxidizing agent: That substance that gets reduced itself or oxidizes the other substances by gaining electrons is called an oxidizing agent.