شرح درس
Chemistry is one of the physical Sciences
CHEMISTRY - Secondary 1
In This part we will study
Measuring tools in the chemistry laboratory
 Chemical experiments are carried out in the chemistry laboratory.
Because they require:
- Safety precautions.
-A source of water.
-A source of heat (e.g. Bunsen flame).

 It is necessary to know how you can use each of these tool.
 The sensitive balance:
- Digital balances are the most common.
- The top loading balance is the most commonly used of the digital balances.

 Beakers:
- Transparent beakers are made of Pyrex glass (heat resistant).
- Some beakers have limited capacity, some of them are graduated (beginning from the top to the bottom).

Usage:
- Mixing the liquids and solutions.
- Transferring a known volume of liquid.

 Graduated cylinders:
Graduated cylinders are made of glass or plastic.
There are cylinders with different capacities, and they are usually graduated (beginning from the top to the bottom).

Usage:
- Measuring the volume of liquids where they are more accurate than flasks.
- Determining the volume of a solid body which doesn't dissolve in water.

How can you determine the volume of a solid body which does not dissolve in water by a graduated cylinder?
• A suitable amount of water is placed in the cylinder and its volume is determined V1
• The solid body is placed in that amount of water carefully inside the cylinder and the produced volume is determined V2
• The volume of the body V= the difference between the produced volume and the volume
of water alone
∴ V=V2 -V1

 Flasks:
• Flasks are made of Pyrex glass, because it resists heat, so they do not break with heating or by the heat of the chemical reactions.
• Flasks have many different capacities.
There are various types of flasks, according to their function and capacity like :

 Burette :
The burette is a long glass tube with two openings, the upper one is used to fill the burette with a solution and the other lower opening has a fixed valve to control the amount of solution taken from it.
• The burette is fixed on a holder with a metallic base to preserve its vertical shape through the experiments.
• In the burette, the graduation zero is close to the upper opening and ends before the valve.
Usage :
- It is used to measure volumes of the solutions with a high degree of accuracy during titration.

 pipette :
- It is a long glass tube opened from the two sides, recorded on it the volume capacity and the error percentage
-They are either graduated or of a predetermined capacity.

Usage:
It is used to accurately measure and transport (transfer) a certain volume of solution.

 Measuring tools for the pH value:

- The term pH refers to the concentration of hydrogen ions H+ in the aqueous solutions.
- Its value ranges from 0 - 14
Usage:
Measuring the value of pH of the solutions is very important in the chemical and
biochemical reactions, because pH value determines if the solution is acidic, basic or neutral.

The value of pH is measured by:
A- The pH test paper tape:
- It is a porous paper saturated with an indicator solution and dried.
- When this paper is wetted with the solution under test, it gains a certain color which indicates a certain pH value.

B- The pH Meter :
- It is more accurate digital apparatus, when it is immersed in the solution, the pH value appears directly on the digital screen.
- The digital pH meter is more accurate than pH test paper in determining pH value of the different solutions, because pH value appears on its screen.

Best wishes to you
Mr.Ahmed Elbasha

كيمياء الصف الاول الثانوي لغات - الفصل الدراسي الاول
شرح كيمياء لغات اولي ثانوي - مستر احمد الباشا