give reasons for the following
Answers
Copper carbonate is green colored which gives copper oxide and carbon dioxide, which are new substances with new properties. This reaction is irreversible, hence it's a chemical change. CUCO3-->CuO+CuO2
When magnesium strip is heated it produces magnesium oxide in air. The composition changes to white powder and the change is irreversible. Hence, it is a chemical change.
Sulphur produces sulphur gas when burnt in air, this acidic product is new and changes the composition of sulphur. Hence, it is a chemical change.
Iron rust is a brown flaky powder formed after iron reacts with air, a new product with new properties is formed which are different from iron metal. Hence, it's a chemical change.
4Fe+302->2Fe203 H2O
When a piece of magnesium strip is dropped in dilute hydrochloric acid, a new product hydrogen gas is evolved and Magnesium chloride has properties different from that of magnesium, which is irreversible and hence, it's a chemical change.
Answer:
1. Copper carbonate [CuCO3] green colour on heating gives copper oxide [Black colour CuO] and CO2. Hence composition is changed new substances CuO [Black] and CO2 with new properties are produced and it is irreversible reaction hence it is a chemical change.
2. When magnesium burns, it is actually reacting with oxygen in the air and not with fire. ... Magnesium reacts with oxygen to make a compound called magnesium oxide. 2Mg + O2 ---> 2MgO. The bright light results because this reaction produces a lot of heat.
3.Sulphur when burnt in air ( complete combustion) forms Sulphur dioxide which is an acidic oxide gas.
4. When an iron nail is exposed to atmosphere then the iron nail reacts with oxygen , water , moisture ,etc. or we can say iron nail go on Oxidation and it will form Iron oxide .
5. When a piece of magnesium strip is dropped in dilute hydrochloric acid, hydrogen gas is evolved and hence it is a chemical change. as new substances, MgCl2 and H2 with new properties are produced and the reaction is irreversible.
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