شرح ساينس الصف الثاني الاعدادي لغات - الفصل الدراسي الثاني
شرح ساينس تانية اعدادي - ترم ثاني

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in this lesson:
Thermal changes accompanying physical changes

When you rub your hands using
- Antiseptic hand gel –
Your hands feel cold G.R
Due to the absorption of heat from the hands when the alcohol present in the hand gel evaporates.
This process is described as endothermic.

When you rub your hands using
- Laundry (detergent) powder [washing powder) and water–
Your hands feel warm G.R
Due to the release of heat during the dissolution of laundry (detergent) powder (washing powder) in water.
This process is described as exothermic.

Thermal changes accompanying the transformations of states of matter

The Refrigeration cycle in the refrigerator
It is a closed and repeated thermal process, in which heat is withdrawn (extracted) from inside the refrigerator and transferred to the surrounding medium (air) using a refrigerant (eco-friendly freons).

This cycle includes endothermic processes and exothermic processes, and the freon passes through several stages as follows:
1. Expansion and evaporation → (endothermic process).
2. Compression
3. Condensation → (exothermic process).
4. The refrigeration cycle is repeated again continuously.

Cooling the food inside the refrigerator by continuously transferring heat from inside the refrigerator to its outside.


The Heat of dissolution
It is the amount of heat absorbed or released when dissolving a specific quantity of solute in a known volume of solvent to form a solution.

Exothermic dissolution
Endothermic dissolution

بالتوفيق
مستر احمد الباشا