Chemistry 8 lesson 13: What is a chemical reaction? The evolution of chemical reactions, examples and exercises. In fact, there are many chemical reactions that the children have seen, such as hitting a match to get a fire, burning fuel, stale food, or watching fireworks on holidays, Tet, etc. …
So what is a chemical reaction? When does a chemical reaction occur, how to identify and how does a chemical reaction take place? Let’s find out through the article below.
I. What is a chemical reaction?
• concept: The process of changing from one substance to another is called a chemical reaction.
The starting substance, which is changed in the reaction, is called the reactant (or reactant).
– New substances produced are called products
• The letter equation of the chemical reaction is as follows:
Names of reactants → Names of products
• Note how to read:
The sign “→” reads to create (or generate)
The “+” sign in front of the “→” sign reads to work with (or react with, chemistry with)
The “+” sign after the “→” sign reads: and
• Examples of chemical reactions:
(1) Sulfur + Iron → Iron(II) sulfide
(Participant) (Product)
⇒ Read: Sulfur reacts with Iron to form Iron(II) sulfide
(2) Calcium carbonate Calcium oxide + carbon dioxide gas
(Participant) (Product) (Product)
⇒ Read as: Calcium carbonate produces calcium oxide and carbon dioxide
• During the reaction, the amount of reactant decreases, the amount of product increases.
II. Evolution of a chemical reaction
– The diagram represents the chemical reaction between hydrogen gas and oxygen gas to form water as follows:
– Figure a) Before reaction; b) During the reaction; c) After the reaction.
In a chemical reaction only the bonds between atoms change, causing one molecule to change into another.
III. When does a chemical reaction take place?
• Conditions for chemical reactions to occur:
When reactants come into contact with each other, a reaction occurs.
– Depending on each specific reaction, it is necessary to heat it to a certain temperature.
Some reactions require a catalyst to speed up the reaction.
IV. How to identify if a chemical reaction has occurred?
– identify chemical reactions occurring based on signals of new substances formed (color, state, exothermic, luminous, …).
V. Exercises on chemical reactions
* Lesson 1, page 50, Chemistry textbook 8:
a) What is a chemical reaction?
b) Which substance is the reactant (or reactant) which is the product?
c) During the reaction, which substances decrease and which increase?
° Solution 1 page 50 Chemistry textbook 8:
a) A chemical reaction is the process of changing from one substance to another.
b) The starting substance, which is changed in the reaction is called the reactant. The newly born substance is the product.
c) During the reaction, the amount of reactants decreases and the amount of products increases.
* Lesson 2, page 50, Chemistry textbook 8:
a) Why can it be said: When the reactant is the reacting molecule (if it is a metal element, the reactant is the reacting metal atom).
b) What change occurs in a reaction? What is the result?
c) According to Figure 2.5 in the lesson, draw the answer: Does the number of atoms of each element remain the same before and after the reaction?
° Solution for lesson 2, page 50, Chemistry textbook 8:
a) When the reactant is the reactant molecule because the particles are composed mostly of substances that are molecules whose molecules fully represent the chemical properties of the substance. Metallic elements have constituent particles that are atoms, so the atom participates in the reaction (creates a bond with the atom of another element).
b) In a chemical reaction only the bonds between atoms change, causing one molecule to change into another. As a result, one substance changes into another.
c) Figure 2.5 is a diagram representing the chemical reaction between hydrogen gas and oxygen gas to produce water: the atomic number of each element remains the same before and after the reaction. The number of H atoms is 4 and the number of oxygen atoms is 2.
* Lesson 3, page 50, Textbook of Chemistry 8: Record the word equation of the reaction that occurs when the candle burns (review exercise 3, lesson 12). Name the reactants and products in this reaction.
° Solution for lesson 3, page 50, Chemistry textbook 8:
The word equation for the reaction:
Paraffin + Oxygen → Carbon Dioxide + Water
– Reactants: paraffin and oxygen gas
– Products: water and carbon dioxide gas
* Lesson 4, page 50, Chemistry textbook 8: Match the following sentences with all the appropriate words in the box:
Before burning, paraffin is in the form (1) … and when burning in the form (2) … the (3) … paraffin reacts with (4) … oxygen gas.
° Solution to lesson 4, page 50, Chemistry textbook 8:
1) solid. (2) relative. (3) molecule. (4) molecules.
* Lesson 5, page 51 of Chemistry textbook 8: Put an egg in a solution of hydrochloric acid and see bubbles in the eggshell.
Know that hydrochloric acid has reacted with calcium carbonate (this substance is found in eggshells) to produce calcium chloride (this substance dissolves) water and carbon dioxide gas is released.
Please indicate the signal that a reaction has occurred. Record the equation in words for the reaction.
° Solution to lesson 5, page 51, Chemistry textbook 8:
The word equation for the reaction:
Hydrochloric acid + Calcium carbonate → Calcium chloride + Water + carbon dioxide gas.
– Substances: Hydrochloric acid and calcium carbonate.
– Products: Calcium chloride, water and carbon dioxide gas.
– signal that a reaction has occurred: the phenomenon of air bubbles.
* Lesson 6, page 51 of Chemistry textbook 8: When coal burns in air, a chemical reaction occurs between carbon and oxygen gas.
a) Explain why it is necessary to pulverize the coal before putting it into the incinerator. Use a fire stick to light it and then fan it vigorously until the coals burn.
b) Record the word equation for the reaction given that the product is carbon dioxide gas.
° Solution for lesson 6, page 51, Chemistry textbook 8:
The word equation for the reaction:
a) Small-sized coal dam to increase the contact surface of coal with oxygen gas, use fire stick to raise the temperature of coal, strong fan to change the air to add enough oxygen. When coal burns, a chemical reaction occurs.
b) Letter equation for the reaction: Coal + oxygen → Carbon dioxide.
Hope with the article on What is Chemical Reaction? chemical reactions, examples and exercises to help children. If you have any suggestions and questions, please leave them in the comments section for Le Hong Phong High School to acknowledge and support, and wish you good luck in your studies.
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Chemistry 8 lesson 13: What is a chemical reaction? The evolution of chemical reactions, examples and exercises. In fact, there are many chemical reactions that the children have seen, such as hitting a match to get a fire, burning fuel, stale food, or watching fireworks on holidays, Tet, etc. … So what is a chemical reaction? When does a chemical reaction occur, how to identify and how does a chemical reaction take place? Let’s find out through the article below. I. What is a chemical reaction? • concept: The process of changing from one substance to another is called a chemical reaction. The starting substance, which is changed in the reaction, is called the reactant (or reactant). – New substances are called products • The word equation of a chemical reaction is as follows: Names of reactants → Names of products • Note how to read: The sign “→” reads to form (or produce) The “+” sign in front of the “→” sign reads as an effect with (or reacts with, combines with) The “+” sign after the “→” sign reads: and • Example of a chemical reaction: (1 ) Sulfur + Iron → Iron(II) sulfide (Participant) (Product) ⇒ Read as: Sulfur reacts with Iron to form Iron(II) sulfide (2) Calciumcarbonate Calcium oxide + carbon dioxide gas (Participant) (Product) (Product) ⇒ Read as: Calciumcarbonate produces Calcium oxide and carbon dioxide • During the reaction, the amount of reactant decreases, the amount of product increases. II. Evolution of a chemical reaction – A diagram representing a chemical reaction between hydrogen gas and oxygen gas to form water is as follows: – Figure a) Before the reaction; b) During the reaction; c) After the reaction. In a chemical reaction only the bonds between atoms change, causing one molecule to change into another. III. When does a chemical reaction take place • Conditions for a chemical reaction to take place: – the reactants come into contact with each other, the reaction takes place. – Depending on each specific reaction, it is necessary to heat it to a certain temperature. Some reactions require a catalyst to speed up the reaction. IV. How to identify if a chemical reaction has occurred? – identify chemical reactions occurring based on signals of new substances formed (color, state, exothermic, luminous, …). V. Exercises on chemical reactions * Lesson 1 page 50 Chemistry textbook 8: a) What is a chemical reaction? b) Which substance is the reactant (or reactant) which is the product? c) During the reaction, which substances decrease and which increase? ° Solution to lesson 1, page 50, Textbook of Chemistry 8: a) A chemical reaction is the process of changing from one substance to another. b) The starting substance, which is changed in the reaction is called the reactant. The newly born substance is the product. c) During the reaction, the amount of reactants decreases and the amount of products increases. * Lesson 2, page 50, textbook of Chemistry 8: a) Why is it said: When the reactant is the reactant molecule (if it is a metal element, the reactant is the reacting metal atom). b) What change occurs in a reaction? What is the result? c) According to Figure 2.5 in the lesson, draw the answer: Does the number of atoms of each element remain the same before and after the reaction? ° Solution for lesson 2, page 50, Chemistry textbook 8: a) When the reactant is the reactant molecule, because the particles are composed mostly of substances that are molecules whose molecules fully represent the chemical properties of the substance. Metallic elements have constituent particles that are atoms, so the atom participates in the reaction (creates a bond with the atom of another element). b) In a chemical reaction only the bonds between atoms change, causing one molecule to change into another. As a result, one substance changes into another. c) Figure 2.5 is a diagram representing the chemical reaction between hydrogen gas and oxygen gas to produce water: the atomic number of each element remains the same before and after the reaction. The number of H atoms is 4 and the number of oxygen atoms is 2. * Lesson 3, page 50 of Chemistry textbook 8: Record the word equation of the reaction that occurs when the candle burns (review exercise 3, lesson 12). Name the reactants and products in this reaction. ° Solution to lesson 3, page 50, Textbook of Chemistry 8: – Letter equation of the reaction: Paraffin + Oxygen → Carbon dioxide + Water – Reactant: paraffin and oxygen gas – Product: water and carbon dioxide gas * Lesson 4 pages 50 Chemistry textbook 8: Match the following sentences with all the appropriate words in the box: Before burning the paraffin is in the form of (1) … and when burning in the form (2) … the (3) ) … paraffin reacts with (4) … oxygen gases. ° Solution 4 page 50 Chemistry textbook 8: 1) solid. (2) relative. (3) molecule. (4) molecules. * Lesson 5, page 51 of Chemistry textbook 8: Put an egg in a solution of hydrochloric acid and see bubbles in the eggshell. Know that hydrochloric acid has reacted with calcium carbonate (this substance is found in eggshells) to produce calcium chloride (this substance dissolves) water and carbon dioxide gas is released. Please indicate the signal that a reaction has occurred. Record the equation in words for the reaction. ° Solution to lesson 5, page 51, Textbook of Chemistry 8: – Letter equation of the reaction: Hydrochloric acid + Calcium carbonate → Calcium chloride + Water + carbon dioxide gas. – Substances: Hydrochloric acid and calcium carbonate. – Products: Calcium chloride, water and carbon dioxide gas. – signal that a reaction has occurred: the phenomenon of air bubbles. * Lesson 6, page 51 of Chemistry textbook 8: When coal burns in air, a chemical reaction occurs between carbon and oxygen gas. a) Explain why it is necessary to pulverize the coal before putting it into the incinerator. Use a fire stick to light it and then fan it vigorously until the coals burn. b) Record the word equation for the reaction given that the product is carbon dioxide gas. ° Solution to lesson 6, page 51, Textbook of Chemistry 8: – The word equation of the reaction: a) Smash the coal to increase the contact surface of the coal with oxygen gas, use a fire stick to raise the temperature of the coal, Strong fan to change the air to add enough oxygen. When coal burns, a chemical reaction occurs. b) Letter equation for the reaction: Coal + oxygen → Carbon dioxide. Hope with the article on What is Chemical Reaction? chemical reactions, examples and exercises to help children. If you have any suggestions and questions, please leave them in the comments section for Le Hong Phong High School to acknowledge and support, and wish you good luck in your studies. Posted by: Le Hong Phong High School Category: Education
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Chemistry 8 lesson 13: What is a chemical reaction? The evolution of a chemical reaction, examples and exercises
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