"Changes and Properties of Matter" Entering the World of Chemistry PPT Courseware 5

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"Changes and Properties of Matter" Entering the World of Chemistry PPT Courseware 5

1. Chemical changes and physical changes

1. Physical changes

⑴Definition: a change that does not produce other substances

⑵Characteristics: No new substances are generated

⑶ Accompanying phenomena: often manifested as changes in form or state

2. Chemical changes

⑴Definition: Changes that produce other substances

⑵Features: New substances are generated

⑶ Accompanying phenomena:

① Often manifested as color change, gas release, and precipitation.

② There are changes in energy, often manifested as luminescence, heat release, and heat absorption.

3. The relationship between physical changes and chemical changes

(1) Difference: whether new substances are generated

(2) Connection: There are physical changes in chemical changes _____

Among physical changes, there are _____ chemical changes

Think: What happens when you light a candle?

What is the change in the explosion?

Determine which of the following changes are physical changes? What are chemical changes?

1. Glass breaking 2. Wood burning

3. Water freezes 4. Copper rusts

5. Alcohol evaporates 6. Iron turns into "molten iron"

7. Human body’s respiration

8. Photosynthesis of plants

9. The electric light emits light 10. Food spoilage

11. Seawater sun salt 12. Dissolved sucrose

13. The disappearance of mothballs 14. Fruit juice extraction

15. Milk turns sour

2. Chemical and physical properties

1. Chemical properties: The properties of substances manifested in chemical changes.

Properties: flammability, stability, corrosiveness, combustion-supporting properties, toxicity, acidity;

2. Physical properties: properties that a substance exhibits without chemical changes.

Properties: color, state, odor, taste, density, hardness, melting point, boiling point, electrical conductivity, thermal conductivity, solubility, ductility, volatility, adsorption type, magnetism, etc.

Which of the following statements are physical changes? Chemical changes? Physical properties? Chemical properties?

1. Nitrogen is a colorless and odorless gas

2. Gas burning

3. Water boils into water vapor

4. Aluminum foil can burn violently in the air

5. The amount of gasoline left open becomes less and less.

Thinking: How to distinguish between oxygen (O2) and carbon dioxide (CO2)?

1) Insert the burning wooden sticks into two bottles of gas respectively. If the wooden sticks burn more vigorously, the gas in the bottle is oxygen. If the burning wooden sticks are extinguished, the gas in the bottle is carbon dioxide.

2) Pour clear lime water into the two bottles of gas respectively and shake. If the lime water becomes turbid, the gas in the bottle is carbon dioxide. If the lime water does not remain turbid, the gas in the bottle is oxygen.

Which of the following statements about physical changes and chemical changes is correct:

A. Physical changes do not produce new matter, but the state of matter must change;

B. During the chemical change process, physical changes must occur at the same time;

C. The change in the dissolution of solid matter in water must be a physical change;

D. As long as there is heat release and other phenomena during the change, the change must be a chemical change;

A solid substance changes into a gaseous substance after being heated. This change belongs to:

A. Physical changes;

B. It may be a physical change or a chemical change;

C. Chemical changes;

D. It is neither a physical change nor a chemical change;

Use a knife to gently cut off a small piece of a certain metal and put it into a beaker filled with water. It is observed that the metal reacts violently with the water, releases heat, and melts itself into silver-white pellets that float on the water. Based on the above description, infer the physical and chemical properties of the metal.

Alcohol is a colorless and transparent liquid with a special smell. It is easily volatile, miscible with water at any ratio, and can dissolve many substances such as iodine and phenolphthalein. Alcohol burns easily and is often used as fuel for alcohol lamps. When an alcohol lamp is lit, the alcohol vaporizes and burns on the wick to produce water and carbon dioxide.

According to the above text description, it can be concluded that the physical properties of alcohol are _____; the chemical properties of alcohol are _______________; the physical changes of alcohol are _______________; and the chemical changes of alcohol are __________.

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Update Time: 2024-10-06

This template belongs to Chemistry courseware People's Education Press Ninth Grade Chemistry Volume 1 industry PPT template

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