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Subjects

Science

Chemical Reactions and Equations

रासायनिक अभिक्रियाएँ और समीकरण

In Class 10 Science, under the chapter Chemical Substances – Nature and Behaviour, this topic introduces chemical reactions as changes that form new substances. Students learn to identify reactants and products, represent reactions through word and chemical equations, and write balanced equations using correct chemical formulae while following the law of conservation of mass.

Practice questions

When black copper(II) oxide is heated with hydrogen gas, it changes into reddish-brown copper. This change is primarily evidence of which process?In the reaction CuO + H₂ → Cu + H₂O, water is formed. What does this show about hydrogen?In the same reaction, one substance loses oxygen and another gains oxygen. What is it called?Which statement about oxidation and reduction is correct?Removal of hydrogen and addition of hydrogen are associated with which processes, respectively?Why can rusting begin when a painted iron surface is scratched?Which of the following equation represents a reaction that is both a combination reaction and an exothermic reaction?Which main chemical reaction causes the change in taste and smell during rancidity of oils and fats?Why can ghee kept in warm open air spoil quickly?Why do foods containing oils and fats remain unspoiled for longer when packed in nitrogen-filled packets?Which problem do antioxidants and airtight packing both reduce?If a container becomes cold during a process and gas is observed evolving, what is the most cautious conclusion?If heat is written on the products side of a chemical equation and the reaction vessel feels warm, what is the nature of the reaction?In a chemical equation, heat energy is written on the reactant side, and one compound breaks down to form two or more products. What type of reaction is this?Why is respiration considered a slow and controlled energy-releasing process compared with combustion?What is the correct difference in energy transformation between photosynthesis and cellular respiration?Which statement correctly distinguishes chewing food with teeth from digesting food by enzymes?Based on the formation of a new substance, what is the correct difference between conversion of milk into curd and conversion of water into ice?Why cannot a chemical reaction be confirmed on the basis of colour change alone?What is the correct respective meaning of upward arrow and downward arrow?