![]() For example, iron and sulphur, when mixed, do not react unless heated. ![]() Heating is necessary for some chemical reactions. But, a vigorous reaction occurs when tartaric acid crystals are added to a solution of baking soda. For example, baking soda powder and tartaric acid crystals do not react when they are mixed. In some cases, chemical reactions occur only when the solutions of the reactants are mixed together. However, sodium and water do not react with each other if they are not in contact. For example, as soon as a piece of sodium comes in contact with water, a reaction takes place to give hydrogen and sodium hydroxide. Some conditions, which, in general, favour a chemical change, are as follows.Ī chemical reaction between two substances takes place when they are in close contact with each other. Let us understand this characteristic of physical changes through, another example.Ĭhemical changes are always accompanied by some external indications such as production of heat or light, precipitation, change in colour or appearance, etc.ĭifferent conditions are necessary to bring about chemical changes in different substances. If you cool a saturated solution of sugar in a refrigerator, you will see that sugar crystals are obtained back. Physical changes are temporary and can be easily reversed. Physical changes have some common features.ġ. Freeze water and it solidifies, and loses its transparency. Press a cardboard box and its shape changes. ![]() ![]() To bring about a physical change some external force or energy has to be applied. ![]()
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |