a A student heated a mixture of iron filings and sulfur strongly. He saw a red glow spread through the mixture as the reaction continued. At the end of the experiment a black solid had been formed. a Explain what the red glow indicates. b Give the chemical name of the black solid. c Write a word equation and a balanced chemical equation to represent the reaction which has taken place. d The black solid is a compound. Explain the difference between the mixture of sulfur and iron and the compound formed by the chemical reaction between them. a a

answer : one can design an experiment using a liquid and an additive that can be added to the liquid and observe the chemical changes in the reaction species.

one would need a beaker which is filled with a known amount of the liquid in which thermometer is placed to measure the temperature changes; after addition of the additive to the liquid solution one can note down the temperature change and find whether the reaction is endothermic or exothermic in nature. by subtracting the initial temperature value with the final temperature one can find the temperature changes.

various combinations of liquid and additive can be used. liquid in this case can be a known quantity of water and additives can be epsom salt or without epsom salt the experiment can be conducted to notice the changes. water and ice, hydrogen peroxide and dry yeast, vinegar and baking soda,etc.