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Since March 2024
Instructor since March 2024
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Mathematics, computer, English, science. I teach primary school
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From 12.36 $ /h
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Education has become a necessity, especially teaching basic subjects such as mathematics, science, and English, subjects that are not difficult to learn or understand. With a little understanding and focus, you will find yourself becoming well acquainted with them, so you must learn and understand them in order to succeed in your professional and academic life.
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At student's location :
  • Around Mecca, Saudi Arabia
Age
Children (7-12 years old)
Teenagers (13-17 years old)
Student level
Beginner
Intermediate
Advanced
Duration
60 minutes
The class is taught in
Arabic
English
Skills
Availability of a typical week
(GMT -05:00)
New York
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At student's home
Mon
Tue
Wed
Thu
Fri
Sat
Sun
00-04
04-08
08-12
12-16
16-20
20-24
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د.
Thermal changes accompanying physical and chemical changes
Thermal changes accompanying physical changes

- melting temperature
It is the temperature change when one mole of solute is dissolved in a given amount of solvent
(The amount of heat energy absorbed or released when one mole of solute is dissolved in a given amount of solvent).
During the dissolution process: two processes occur:
A- Dissociation: the breaking of bonds (endothermic reaction)

Sodium and chloride ions dissociate from the crystal lattice as a result of the ionic bond breaking.
The energy absorbed to break the bond is called the heat of the crystal lattice (bond energy).
- Crystal lattice temperature: It is the energy needed to break the bond between ions in the crystal lattice.

B- Hydration: The dissociated ions bind with water molecules to form hydration ions (exothermic process).

Rehydration temperature:

It is the amount of heat released when hydrating ions bind to water molecules.
If the crystal lattice temperature > heat of hydration

Dilution temperature:
It is the heat change per mole of solute when diluted from a concentrated solution to a dilute solution.
(It is the heat change of one mole of solute when diluted in a large amount of water (about 1000 moles of solvent)).

Sedimentation temperature:
The amount of heat released when one mole of an insoluble substance is completely precipitated.

- heat of combustion
It is the amount of heat released when one mole of a substance is completely burned in an abundance of oxygen. (The reaction is always exothermic).

Formation temperature:
It is the amount of heat released or absorbed when one mole of a compound is formed from its elemental elements so that the elements are in their standard state. (at 25 °C, a pressure of 76 x g).

Note:
Heat of formation of the elements = zero
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د.
Thermal changes accompanying physical and chemical changes
Thermal changes accompanying physical changes

- melting temperature
It is the temperature change when one mole of solute is dissolved in a given amount of solvent
(The amount of heat energy absorbed or released when one mole of solute is dissolved in a given amount of solvent).
During the dissolution process: two processes occur:
A- Dissociation: the breaking of bonds (endothermic reaction)

Sodium and chloride ions dissociate from the crystal lattice as a result of the ionic bond breaking.
The energy absorbed to break the bond is called the heat of the crystal lattice (bond energy).
- Crystal lattice temperature: It is the energy needed to break the bond between ions in the crystal lattice.

B- Hydration: The dissociated ions bind with water molecules to form hydration ions (exothermic process).

Rehydration temperature:

It is the amount of heat released when hydrating ions bind to water molecules.
If the crystal lattice temperature > heat of hydration

Dilution temperature:
It is the heat change per mole of solute when diluted from a concentrated solution to a dilute solution.
(It is the heat change of one mole of solute when diluted in a large amount of water (about 1000 moles of solvent)).

Sedimentation temperature:
The amount of heat released when one mole of an insoluble substance is completely precipitated.

- heat of combustion
It is the amount of heat released when one mole of a substance is completely burned in an abundance of oxygen. (The reaction is always exothermic).

Formation temperature:
It is the amount of heat released or absorbed when one mole of a compound is formed from its elemental elements so that the elements are in their standard state. (at 25 °C, a pressure of 76 x g).

Note:
Heat of formation of the elements = zero
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