"Law of Conservation of Mass" Chemical Changes and Their Representation PPT Courseware

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"Law of Conservation of Mass" Chemical Changes and Their Representation PPT Courseware

Elements and atoms of chemical changes

New substances are generated during chemical changes, so do the types of elements change during chemical changes?

Inquiry activities

It is known that candles contain C and H elements, and oxygen contains O elements. Can you design a simple experiment to prove whether the products after burning candles still contain these elements?

1. Predict the products of candle burning:

Candles burn to produce CO2 and H2O.

2. Design the experimental plan for product verification:

(1) Light the candle;

(2) Cover the flame with a dry and cold beaker

(3) Cover the flame with a beaker coated with clarified lime water

Think about it:

What happens when water is decomposed by electricity?

Molecule-→Atom--→New Molecule--→New Substance

1. Ask questions:

The types of elements do not change during chemical changes, and the types and numbers of atoms do not change. So does the mass of each substance change during chemical changes?

Mass determination of white phosphorus before and after combustion

Literal expression: phosphorus + oxygen → phosphorus pentoxide

Phenomenon: A large amount of white smoke and a large amount of heat are emitted. The balloon bulges and then deflates, but the scale remains balanced.

think about it

1. Why is the bottom of the Erlenmeyer flask covered with fine sand?

2. What is the function of glass tube?

3. What happens to the balloon? Why does this happen?

4. Can the glass tube be replaced with a glass rod without a balloon attached to one end?

Key points of the concept of the law of conservation of mass:

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. "Sum" means counting the reactants and products in various states. Gases such as precipitation and invisible to the naked eye should also be considered.

2. The sum of the masses of each substance participating in a chemical reaction is not the sum of the arbitrary masses of each substance, and the mass of substances not participating in the reaction cannot be calculated.

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

What is the scope of application of the law of conservation of mass? What use does learning this law have for us?

The law of conservation of mass applies to all chemical reactions.

applicable laws

1. Make relevant calculations

2. Speculate the composition of some substances

3. Explain some experimental facts

A simple application of the law of conservation of mass.

1. When 6g of carbon is burned in sufficient oxygen to produce 22g of carbon dioxide, ____g of oxygen participates in the reaction.

2. Heat a mixture of 25 g potassium chlorate and 1 g manganese dioxide until it is completely decomposed and the residual solid mass is 14 g, then ____g of oxygen is produced.

3. It is known that paraffin is the main component of candles. The products of complete combustion of candles in the air are CO2 and H2O. It is judged that paraffin must contain _______ elements and may contain ___ elements.

4. In the chemical reaction 2XY2+Y2=2Z, the chemical formula of Z is ( )

A.X2Y3 B.XY3

C、X2Y6 D、X2Y4

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Update Time: 2024-11-20

This template belongs to Chemistry courseware Hunan Education Edition Ninth Grade Chemistry Volume 1 industry PPT template

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