"Law of Conservation of Mass" Chemical Changes and Their Representation PPT Courseware 2

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"Law of Conservation of Mass" Chemical Changes and Their Representation PPT Courseware 2

One day, Holmes was smoking his pipe as usual, and the room was filled with the pungent smell of smoke. Watson asked: "Dear sir, others say you are very smart, so can you tell me how heavy the smoke you exhale weighs?"

Ask the students to think about how Holmes answered?

Holmes said slowly: "This question is very simple. I only need to weigh the total weight of the pipe and tobacco before smoking, and then subtract the total weight of the pipe and remaining ash after smoking. Isn't it the weight of the smoke I exhale!"

m pipe + m cut tobacco =?= m pipe + m ash + m cigarette

Exploration experiment

The total mass of each substance before the reaction =? = the total mass of each substance after the reaction

Before conducting experiments, you should consider:

1. Experimental purpose

2. What experimental instruments and devices

3. Main operating steps

Solution design (experimental steps)

Experiment 1

Experimental steps

1. Weigh the total mass of white phosphorus, Erlenmeyer flask, rubber stopper, and balloon before reaction.

2. Heat the lower end of the glass tube red in the flame outside the alcohol lamp, quickly plug the bottle stopper, ignite the white phosphorus, and observe the phenomenon.

3. After the Erlenmeyer flask has cooled, place it on the balance again and weigh it.

Experimental phenomena (P91)

① White phosphorus burns and produces a large amount of white smoke; the balloon first inflates, then becomes smaller, and finally collapses.

② After the reaction, balance the balance.

think:

① Changes and causes of balloons

② The role of the balloon - to prevent the rubber stopper from being blown open

③ The role of fine sand - to prevent the Erlenmeyer flask from exploding due to uneven heating

get rules

1. Law of conservation of mass (page 91 of the textbook)

Numerous experiments have proven:

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.

P + O2 → P2O5

Fe + CuSO4 → Cu + FeSO4

1. The law of conservation of mass applies only to chemical changes.

2. "Mass" must be the mass of the substance that actually participates in the chemical reaction, rather than the simple sum of the masses of each substance.

3. Sum: The gas "gas product CO2 H2 O2" in the reactants or products cannot be ignored.

4. It is "mass conservation", not volume conservation.

practise:

1. In the chemical reaction A + B = C,

4g 12g

Then the mass of B participating in the reaction is ( )

A.6 grams B.8 grams C.10 grams D.16 grams

2. The phenomenon that cannot be explained by the law of conservation of mass is ( )

A. Dry wet clothes in the sun

B. The iron wire burns and its solid mass increases

C. After potassium permanganate is heated, the solid mass decreases

D. After the candle burns, it becomes shorter and shorter and eventually disappears

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Update Time: 2024-10-03

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

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