"The Composition of Water" PPT

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"The Composition of Water" PPT

Part One: Review:

1. Judgment of physical changes and chemical changes

(1) Among the following phenomena, which one is a chemical change ( )

A. Broken glass B. Flat tire

C. Gas combustion D. Air liquefaction

(2) Which of the following processes is a physical change ( )

A. The burning of coal B. The melting of ice into water

C. Candle burning D. Food spoiled

(3) When a substance undergoes a chemical change, there must be ( )

A. Color change

B. Gas, precipitation or water generation

C. Emit heat and light

D. Generation of new substances

2. During the water cycle, water undergoes ____ (fill in "physical" or "chemical" changes, because water ____ (fill in "with" or "without") changes into other substances during the process, which just happens ______Variety.

3. Please briefly answer the main contents of the molecular kinetic theory.

(1) A molecule is a particle that constitutes a substance and is very small.

(2) Molecules are constantly moving irregularly

(3) There are gaps between molecules

The composition of water PPT, part 2 content: Experimental exploration: electrolysis of water

1. Water electrolysis device

The glass tube is filled with water (a small amount of sodium hydroxide or dilute sulfuric acid solution is added to enhance the conductivity of the solution.)

Glass tube with piston on top (with scale)

Connect to the negative and positive poles of the DC power supply respectively.

2. Observation content and steps

A. Phenomenon produced on the electrode:

B. Changes in the liquid level in the two glass tubes:

C. The volume ratio of the two gases produced:

D. Different methods used to verify these two gases

E. Different phenomena that appear:

The composition of water PPT, the third part: observation content and steps

A. Phenomenon produced on the electrodes: A large number of bubbles are produced on both poles, and the bubbles produced by the negative electrode are faster and more numerous than those produced by the positive electrode.

B. Changes in the liquid levels in the two glass tubes: The liquid levels in both glass tubes are falling, but the liquid level in the negative electrode drops faster.

C. The volume ratio of the two gases produced: Their volume ratio is: V positive: V negative = V oxygen: V hydrogen = 1:2

D. Different methods used to verify these two gases

Ignite directly (hydrogen). Use a wooden stick with sparks to get close to (oxygen).

E. Different phenomena that appear:

Light blue flame (when impure, there will be a sharp explosion sound) (hydrogen)

Re-ignition of wood sticks (oxygen)

The composition of water PPT, the fourth part: the composition of water molecules

1. Recall and discuss what particles water, hydrogen, and oxygen are made of.

2. The particles that make up these substances are very small, but are there smaller particles among these particles?

Based on the schematic diagram of the water electrolysis process and experimental phenomena, analyze how water decomposes to produce hydrogen and oxygen when electricity is supplied.

A water molecule contains two hydrogen atoms and one oxygen atom

Water molecules are made up of hydrogen atoms and oxygen atoms

Water is composed of hydrogen and oxygen

During the electrolysis of water, water molecules change, but hydrogen atoms and oxygen atoms do not change.

The composition of water PPT, Part 5: Consolidation exercises:

1. Regarding the experiment of electrolyzing water, which of the following descriptions is correct ( )

(A) The positive electrode produces a flammable gas

(B) The volume of gas generated by the negative electrode is twice that of the positive electrode gas

(C) The gas produced by the negative electrode can re-ignite the wood strips with sparks

(D) This experiment proved that water is composed of hydrogen and oxygen

2. If a total of 48 ml of gas is collected by electrolyzing water, how many ml of oxygen is obtained?

3. Theoretically, the volume ratio of hydrogen and oxygen generated during electrolysis of water is 2:1, but the experimental data shows that the volume ratio of hydrogen and oxygen is slightly greater than 2:1. Based on this finding, do you think the following practices are undesirable? is ( )

A. Repeat experiments many times to find out the reason.

B The data obtained from the experiment are similar to the theory, and the experiment can be considered successful.

C Make a bold hypothesis: Oxygen is more soluble in water than hydrogen

D. Check whether the experimental device is leaking

4. Which of the following statements about the composition of water is correct ( )

(A) Water is composed of hydrogen and oxygen

(B) Water is composed of hydrogen molecules and oxygen atoms

(C) Water is composed of water molecules

(D) Water is composed of water elements

5. The gas that can cause sparks to re-ignite is ( )

(A)Hydrogen gas

(B) In the water electrolysis experiment, the gas generated on the electrode connected to the positive electrode of the power supply

(C)Air

(D) In ​​the water electrolysis experiment, the gas generated on the electrode connected to the negative electrode of the power supply

The composition of water PPT, part 6: expand and improve

Which of the two gases is oxygen? Which one is air? How do we verify these gases?

Put wooden sticks with sparks into the bottles respectively. Oxygen can make the wooden sticks re-ignite, but air cannot.

Testing of hydrogen gas

Ignite it with a burning stick and the gas produced by it will burn with a light blue flame is hydrogen (when the hydrogen is impure, there will be a sharp popping sound)

Keywords: Zhejiang Education Edition eighth grade science PPT courseware free download, composition of water PPT download, .PPT format;

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Update Time: 2024-11-12

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