Chemical Reactions التفاعلات الكيميائية

1 What is a chemical reaction?

A reaction rearranges atoms into different substances. Bonds break in the reactants, and new bonds form in the products.

يعاد ترتيب الذرات لتكوين مواد جديدة؛ تتكسر روابط في المتفاعلات وتتكون روابط في النواتج.

2 Physical or chemical change?

Possible clues to a chemical reaction include heat or light, or formation of a new gas, liquid or solid.

3 The key distinction

Does the substance's composition change? هل تغيّر تركيب المادة؟

4 Read the sides

The left side shows what you start with; the right side shows what is formed.

5 Conservation of mass

Matter is not created or destroyed in a chemical reaction. A balanced equation has the same number of atoms of each element on both sides.

عدد ذرات كل عنصر متساوٍ على جانبي المعادلة الموزونة.

Glucose + oxygen → carbon dioxide + water

6 Coefficient or subscript?

Coefficient: number before a formula, e.g. the 6 in 6O₂. Subscript: small number within a formula, e.g. the 2 in O₂.

Balance with coefficients; keep the chemical formulas unchanged. وازن بالمعاملات مع الحفاظ على الصيغ.

7 Where does the energy go?

Bonds are broken and formed as reactants become products. This is accompanied by an energy change.

يتغير مقدار الطاقة خلال تكسر الروابط وتكوّن روابط جديدة.

8 Activation energy

The minimum energy needed for reactants to form products is activation energy. Even a reaction that releases energy needs this initial input.

طاقة التنشيط هي الحد الأدنى من الطاقة اللازمة لبدء التفاعل، حتى لو كان التفاعل يطلق الطاقة بعد ذلك.

9 Reading an energy diagram

The vertical axis shows energy; the horizontal axis shows reaction progress. The rise from the reactants to the peak represents activation energy.

12 Compare at a glance

13 A biological catalyst

A catalyst lowers the activation energy needed to start a reaction. An enzyme is a biological catalyst, usually a protein, that speeds up biochemical reactions.

الإنزيم حفاز حيوي يخفض طاقة التنشيط ويزيد سرعة التفاعل الكيميائي الحيوي.

14 Same reaction, lower barrier

The enzyme is not used up and can be reused; it does not increase the amount of product made.

15 Examples from the book

16 Substrate → products

Substrates bind to the enzyme's active site. The site changes shape; an enzyme–substrate complex forms. Products are released, leaving the enzyme available again.

شكل الموقع النشط ملائم للمادة المتفاعلة، ثم تتكون النواتج وتنطلق.

17 What changes enzyme activity?

18 Connect the lesson

Reactants form products → activation energy starts the reaction → enzymes lower that energy barrier. المتفاعلات تكوّن نواتج، وطاقة التنشيط تبدأ التفاعل، والإنزيمات تخفض حاجز الطاقة.