The reaction of copper sulphate with iron produced two new substances, i.e. When the magnesium ribbon was burnt, the ash was the new substance formed. In all these activities, we saw that in each change, one or more new substances are formed. When baking soda (NaHCO 3) reacts with vinegar which contains acetic acid carbon dioxide comes out, which turns lime water milky, therefore it is a chemical change. Now, we shall perform some activities to show the chemical changes where new substances are formed. It is different from iron on which it gets deposited. In the kitchen, a wet iron pan (tawa) often gets rusted if left in that state for some time. The agricultural tools such as spades and shovels, also get rusted when exposed to the atmosphere for some time. We can usually see iron gates of parks or farmlands, iron benches kept in lawns and gardens, almost every article of iron, kept in the open gets rusted. It acquires a coating of a brownish substance called rust and the process is called rusting. Almost every iron (or steel) object kept in the open gets rusted slowly. All the new substances which we use in various fields of our life are produced as a result of chemical changes (or chemical reactions).Ī change with which we are quite familiar is the rusting of iron. A chemical change occurs when two substances react chemically to form a new substance with different chemical properties. Very little energy (heat, etc) is either absorbed or evolved.Ĭhemical changes are also called chemical reactions.A temporary change in colour may take place.It is a temporary change and is generally reversible.No new substance is formed in this change.Thus, we noticed that the important characteristics of physical changes are as follows: In such a change, no new substance is formed. The physical changes are temporary changes which can be easily reversed to form the original substance. First, we shall perform some activities to show the physical changes that are taking place all around us are: In a physical change, a substance undergoes changes only in its physical properties such as shape, size, colour and state, and no new substance is formed. Some changes that we have noticed around us are melting of ice, making of ice cream, melting of wax, stretching a rubber band, evaporation of water, cutting of paper, breaking of glass pane, bending of glass tube by heating, boiling of water, sublimation of camphor, etc. Similarly, setting of curd from milk is a change. These changes may involve one or more substances. CBSE Class 7 Science Notes Chapter 6 Physical and Chemical ChangesĮvery day we come across many changes that are taking place all around us. Here we have given NCERT Class 7 Science Notes Chapter 6 Physical and Chemical Changes.
#Examples of chemical changes pdf
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#Examples of chemical changes pdf download
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