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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

Why do chips remain fresh for a longer time in a nitrogen-filled packet?What is the common purpose of antioxidants and airtight packing in food?If the reaction vessel becomes very cold during a chemical reaction, what is the correct conclusion about the energy change?If heat is written on the products side of a chemical equation, what is the nature of the reaction?If heat is shown as a reactant on the left side of a chemical equation and one compound breaks down to form two or more products, what is the correct identification of the reaction?Why can combustion and respiration be considered similar on the basis of energy?What is the correct energy based difference between photosynthesis and respiration?A student placed an iron nail in a blue copper sulphate solution. After some time, a reddish-brown coating appeared on the nail and the solution turned green. Which is the correct conclusion from this observation?On what basis do curd formation from milk and ice formation from water differ?Why should a chemical reaction be confirmed carefully when only a colour change is observed?In a chemical equation, what do a downward arrow and an upward arrow respectively indicate?Which statement about the reaction \(\mathrm{Fe + CuSO_4 \rightarrow FeSO_4 + Cu}\) is correct?In the reaction CuO + H₂ → Cu + H₂O, which statement is correct with respect to oxidation and reduction?Which arrangement is most suitable for demonstrating the law of conservation of mass experimentally?In an open container, the measured mass after a reaction is lower because a gas produced escapes. Which conclusion is correct?Why are coefficients, rather than subscripts, changed when balancing a chemical equation?If a chemical equation has the same number of hydrogen atoms on both sides but an unequal number of oxygen atoms, what is the correct conclusion?How many oxygen atoms are required to form two water molecules?In two formula units of magnesium oxide, what is the ratio of magnesium atoms to oxygen atoms?Why is a magnesium ribbon cleaned with sandpaper before burning?