(i) Butter turning rancid – The composition of butter changes in this change. (g) Occurrence of lightning – Energy is produced in this change. (d) Rotting of eggs – Change in composition of the content of eggs, and it is irreversible. (c) Respiration in mammals – Inhalation of oxygen and exhaling carbon dioxide, which is irreversible and composition of oxygen changes. The following changes are chemical changes: (m) Preparation of carbon dioxide from calcium carbonate & dilute hydrochloric acid.
(k) Crystallisation of a salt from its solution. (a) Vaporisation of water into water vapour. Select the chemical changes from the following list of changes Magnetization of iron is a temporary change, which does not change the composition of iron but only physical properties. (c) Iron rust has a different composition from iron and has new properties, which cannot be reversed.
The reaction between zinc and nitric acid produces H2 gas which gets oxidized causing a chemical change. (b) Zinc nitrate dissolves in water and hence is a physical change. Magnesium reacts with Oxygen in the air and forms magnesium oxide which cannot be undone. When cooled it retains its earlier color and it does not react easily with oxygen in the air. (a) When Platinum gets heated, it changes color. (c) Rusting of iron is a chemical change but, magnetization of iron is a physical change. (b) Addition of zinc nitrate to water is a physical change but, addition of zinc to dilute nitric acid is a chemical change. (a) Heating a platinum wire is a reversible change but, heating a magnesium wire is an irreversible change. Boiling will also not work as CaCo 3 is in solid form in water. (e) we take calcium carbonate the above experiment cannot be possible as no new substance with new properties is produced, since CaCo 3 is insoluble in water. (d) No, the composition and properties are not altered. (e) Give a reason why the above experimentation would not be possible, if calcium carbonate is taken, in place of potassium chloride. (d) Are the composition and properties of the original substance altered. (c) Is the change reversible or not reversible. (b) Name the residue which remains behind after the salt solution is boiled. (a) Is the above change physical or chemical A salt solution is obtained which is then boiled leaving behind a residue. Potassium chloride is added to water and stirred. Conversion of solid into a liquid on heating.Conversion of liquid into vapour or gas.Conversion of a solid into a liquid on heating.Conversion of a liquid into a vapour or gas.State which of the following terms connected with change of state of matter ie. Give reasons.Ĭhange in state of matter is a physical change because of the physical condition and appearance changes but not the chemical composition. Is change of state of matter – a physical or a chemical change.
Such energy is generally absorbed or released during the chemical change. Physical Change: There is no addition or deduction of energy during the physical change, but the energy required for completion of change is released when the change is reversed.Ĭhemical Change: Energy like light, pressure, heat energy is required for chemical changes. Heat energy is required for this chemical change.Ĭompare the energy changes involved during a physical and a chemical change.A new product is formed with new properties, i.e.It is an irreversible change, as after burning the ribbon cannot be unburnt.
Give four reasons why burning of a magnesium ribbon in air is considered a chemical change.īurning of magnesium ribbon in air is a chemical change because: (g) The composition and properties of the original substance care not altered. (e) Produces one or more new substances by change in its composition. (g) The composition and properties of the original substance are not altered. (e) Produces one or more new substances by change in its composition State which of the following pertain to – chemical changes.
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