"Conditions of Combustion" Fuel and its Utilization PPT Courseware 4

"Conditions of Combustion" Fuel and its Utilization PPT Courseware 4

Purpose

1. Deepen your understanding of combustion conditions and further understand the principles of fire extinguishing.

2. Experience the process of experimental inquiry.

Beaker, tweezers, crucible tongs, alcohol lamp, tripod, thin copper sheet, alcohol, cotton, table tennis balls, filter paper, candles.

1. Combustion conditions are related to the properties of the substance

Dip cotton in alcohol and water respectively and place it over the flame of an alcohol lamp to heat for a while.

① Experimental phenomenon: Cotton dipped in alcohol _____, cotton dipped in water ________.

②Experimental conclusion: One of the conditions for combustion is that the substance must be _______.

2. Combustion conditions are related to temperature

(1) Take a small piece of table tennis and filter paper, clamp them with crucible pliers, and heat them on the flame of an alcohol lamp.

① Experimental phenomenon: Table tennis fragments and filter paper fragments ________.

②Experimental conclusion: Table tennis fragments and filter paper fragments are both ________.

(2) Cut a small piece from the table tennis ball and the filter paper, place them on both sides of a thin copper sheet, and heat the copper sheet.

① Experimental phenomenon: table tennis fragments _______, filter paper fragments _____.

②Experimental conclusion: One of the conditions for combustion is _______________________.

1. Ordinary handkerchiefs are made of cotton and are easily flammable when exposed to fire. But if the handkerchief is soaked in alcohol mixed with a certain amount of water and then ignited, we can see that the handkerchief ignites a fire without burning. Based on the burning conditions, can you explain why?

Tip: When you soak a handkerchief in this mixture and burn it, the alcohol is burned. Due to the presence of a certain amount of water, both alcohol and water gradually evaporate into vapor. Water vapor cannot burn, which reduces the concentration of alcohol vapor and generates less heat. In addition, due to the presence of water, part of the heat generated when alcohol burns is absorbed by the water, causing the water to change from liquid to gas, thereby greatly reducing the temperature of the flame and making the temperature of the flame lower than the ignition point of the handkerchief. Therefore, although the flame is raging, the The handkerchief was undamaged.

2. There is a burning candle. Based on the burning conditions of the substance, what methods can you think of to extinguish the candle, and what principles are used in each?

Tips: (1) Blow out, fan out, or douse with water to lower the temperature below the ignition point of the candle;

(2) Extinguish by covering it with a large beaker, covering it with sand, covering it with a wet cloth, or using carbon dioxide to isolate oxygen;

(3) Cut off the candle wick to isolate flammable materials.

Experimental drill

1. No matter how you heat the iron wire in the air, the iron wire will only turn red and will not burn. However, if you put the red-hot iron wire in a gas bottle containing oxygen, it will shoot out sparks and burn violently. In this regard, the following explanation is correct ( )

A. Because the iron wire will not reach its ignition point when placed in the air

B. Because the air contains the fire extinguishing agent carbon dioxide

C. The ignition point of the wire is too high

D. The oxygen concentration in the gas cylinder is high, which expands the contact area between the iron wire and oxygen; at the same time, in a certain space, the number of collisions between the iron wire and oxygen molecules greatly increases, so that the combustion reaction can occur violently

2. Lighters bring convenience to people’s lives. The picture below is a physical photo of an ordinary electronic lighter. The following combinations that meet the combustion conditions and can start a fire are ( )

A.①③⑤ B.①③④

C.①②③ D.①②④

3. The fire extinguishing bomb is a safe fire-fighting equipment without detonators and explosives. It is ignited by superconducting material. When using it, peel off the upper cover to expose the superconducting heat-sensing material, and throw it into the fire scene. The moment it encounters fire, the projectile will Splits open to release ultra-fine dry powder and highly effective fire extinguishing agent. The active ingredient of the fire extinguishing agent is sodium bicarbonate, which decomposes when heated to produce a large amount of carbon dioxide gas, as well as sodium carbonate and water.

(1) The fire extinguishing principle of fire extinguishing bombs is ____________________.

(2) During the fire extinguishing process, the firefighters also used a handheld wind fire extinguisher, which uses gasoline as fuel and sprays high-speed airflow similar to level 12 wind to blow out the fire. The fire extinguishing principle of the fire extinguisher is ____________________.

(3) Firefighters are often unbearably roasted during the process of putting out fires and need to constantly pour water on themselves. The reason why watering can lower the temperature is _______________.

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