"Law of Conservation of Mass" Chemical Equations PPT Courseware 6

Description

"Law of Conservation of Mass" Chemical Equations PPT Courseware 6

learning target

1. Able to explain the content of the law of conservation of mass through inquiry activities

2. Understand the essence of the law of conservation of mass from a microscopic perspective

3. Application of the law of conservation of mass

Review the past and learn the new

What is scientific inquiry?

Scientific inquiry: The process of formulating conjectures and hypotheses about an unknown problem, and using scientific experiments to verify whether the hypotheses are true.

What scientific inquiry experiments have we done or learned?

An exploration of candles and their burning

The study of the air inhaled and exhaled by the human body

A study of the oxygen content in the air

Study on the preparation of oxygen and its properties

An investigation into determining the composition of water

Ask a question

When a substance undergoes a chemical change, what is the relationship between the sum of the masses of the reactants and the sum of the masses of the products?

Consult information (preparation before experiment):

Option 1: White phosphorus spontaneous combustion

① White phosphorus (highly toxic and easy to spontaneously ignite) is stored in water and is taken out with tweezers.

② In order to prevent the bottom of the Erlenmeyer flask from breaking when burning, a layer of fine sand should be spread at the bottom of the Erlenmeyer flask.

③The combustion of white phosphorus consumes oxygen in the air, so the experiment must be carried out in a closed container.

④The function of the balloon: buffering effect, preventing the gas from expanding, increasing the pressure inside the bottle, and popping out the rubber stopper.

Think: Do all chemical reactions obey the law of conservation of mass?

Mass determination before and after the reaction of dilute hydrochloric acid and sodium carbonate

Experimental steps

①Put the small test tube containing hydrochloric acid into the small beaker containing sodium carbonate powder, place it on the balance tray, and adjust the balance;

② Remove the small beaker and tilt it to allow the hydrochloric acid and sodium carbonate in the small test tube to react;

③After a period of time, place the beaker on the balance again and observe the change of the scale pointer.

Mass determination of magnesium ribbon before and after burning

Experimental steps

① Take a magnesium strip polished with sandpaper and an asbestos mesh, put them together on the balance and weigh them;

② Light the magnesium strip above the asbestos mesh;

③Weigh the products after burning the magnesium strips together with the asbestos net on the balance, and observe the change of the scale pointer.

When understanding the definition of the law of conservation of mass, please note:

The sum of the masses of each substance participating in a chemical reaction is equal to the sum of the masses of each substance produced after the reaction.

1. Each substance that participates in a chemical reaction means that the mass of substances that do not participate in the reaction cannot be calculated.

2. The law of conservation of mass applies to all chemical changes, and physical changes are outside the scope of discussion.

3. The "conservation" of the law of conservation of mass refers to the conservation of mass, not the conservation of volume, number of molecules, or other aspects.

4. "Sum" means counting the reactants and products in various states. Such as gas or precipitation should also be considered.

3. Application of the law of conservation of mass:

1. Determine the types of elements that make up a substance

1. A certain compound decomposes completely when heated to produce KCl and O2. Infer the elements contained in the compound: ________.

2.1.6g of a substance burns in oxygen to produce 1.8gH2O and 4.4gCO2. Try to deduce that the constituent elements of this substance are ________.

3. When a substance is heated and decomposes to produce copper oxide and water, then all the elements contained in the substance are ( )

A. Cu, O, H B. Cu, O C． O.H D． Cu,H

2. Infer the chemical formula of reactants or products

1. In the chemical reaction 2XY2+Y2=2Z, the chemical formula of Z is ______

2. As shown in the picture on the right, every two molecules of A react to produce two molecules of B and one molecule of C. It is known that A, B, and C are different types of pure substances, then the chemical formula of substance B is ( )

A.A2B B.AB2

C、AB D、A4B2

practise

1) Substance A is decomposed by heat to produce ammonia, water and carbon dioxide. The elements that make up substance A are ( )

2) If a combustible material burns in oxygen to produce carbon dioxide and water, the combustible material must contain ( ) elements and may contain ( ) elements;

3) If a combustible material burns in oxygen to produce carbon monoxide, carbon dioxide and sulfur dioxide, the combustible material must contain ( ) elements and may contain ( ) elements;

4) If a combustible material burns in oxygen to generate sulfur dioxide and water, the combustible material must contain ( ) elements and may contain ( ) elements;

How to read chemical equations

(1) Macroscopic reading: Carbon and oxygen produce carbon dioxide under ignition conditions

(2) Quantitative reading: every 12 parts of carbon by mass react with 32 parts by mass of oxygen to produce 44 parts by mass of carbon dioxide

(3) Microscopic reading: every carbon atom reacts with an oxygen molecule to generate a carbon dioxide molecule

1. A formula that expresses a chemical reaction using a chemical formula is called a chemical equation.

2. The chemical equation shows:

①Reactants, products and reaction conditions;

②The quantitative relationship between the particles participating in the reaction;

③Indicates the mass relationship between substances, that is, the mass ratio between substances, expressed by relative molecular mass (or relative atomic mass).

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Update Time: 2024-06-30

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