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POINTS TO REMEMBER
* Particle arrangement within the state of matter gets disturbed upon heating. The disturbance is seen either as expansion or contraction.
* A process in which liquid changes into vapour on heating is called evaporation.
* A process in which solid changes into liquid on heating is called melting or fusion.
* A process in which gas changes into a liquid is called condensation.
* A process in which liquid changes into solid is called freezing.
* Physical changes are the changes in which only physical properties of a substance undergo a change and there is no change in its chemical composition.
* Solid substances are usually purified by the process of crystallization.
* Evaporation is the technique used to separate dissolved solids from a solid-liquid mixture.
* Certain solid substances like camphor, naphthalene get converted into gas directly without becoming liquid upon heating by sublimation.
* Changes that occur with the formation of new substance with different chemical composition or transformation of a substance into another substance with the evolution or absorption of heat or light energy are termed as chemical changes.
* Changes that repeat themselves after a definite interval of time are called periodic changes.
* Changes that do not repeat themselves after a definite interval of time and occur randomly are called non-periodic changes.
* Changes in which heat is absorbed are known as endothermic changes.
* Changes in which heat is released are known as exothermic changes.
CHANGES AROUND US
This activity helps the students to understand the effect of heat on matters
Step 1: Type the URL link given below in the browser or scan the QR code. A page opens with a glass full of ice with a play button near to it.
Step 2: Press Play button. It opens into another page with the set up of temperature and change of phases.
Step 3: Set the temperature and phases. Press the play button below.
Step 4: Do it with different options. Then a next page button will come
Step 5: Go there you will end with a small quiz.
Changes Around Us URL:
*Pictures are indicative only
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