The existence of air in the first quarter
Air has quality.
Question: All substances have mass, so does air also have mass? Conclusion: Air has quality.
2, the use of air:
Examples of uses: (1) for biological respiration and plant photosynthesis (2) for wind, clouds and other weather phenomena.
(3) Air is needed for burning materials. (4) Air is needed for balloon lift-off, kite flying and parachute landing. (5) Air is needed for flying, gliding and sailing. (6) Drink drinks and fill ink with a pen.
(x) the existence of atmospheric pressure
Experiment 1: "Cup lid experiment"
Practice: ① Put a piece of cardboard on an empty cup, turn the device upside down and find that the cardboard will fall off;
(2) If the opening of the cup is sealed with cardboard after it is filled with water, quickly turn the device upside down and find that the paper has not fallen.
Thinking: The difference between the two experiments is that there is no water in the former cup, but there is air, and the latter bottle is full of water.
The difference between the two results should be due to this reason. It is precisely because of the atmospheric pressure that the paper is pressed against the cup mouth and the paper will not fall off. In the first experiment, because there is air in the bottle, the internal and external pressures will cancel each other out, and the paper will fall due to its own gravity. This experiment fully proves the existence of atmospheric pressure.
Experiment 2: "The jar was crushed by air"
Practice: After an empty jar is filled with a small amount of water, put this device on an alcohol lamp and heat it until the water in it boils. then
Quickly put out the alcohol lamp and block the jar mouth with the flour dough prepared in advance. You can immediately see the cans being crushed with a "crackling" sound.
Thinking; In the process of heating the water in the cylinder with alcohol lamp, most of the air in the cylinder is squeezed out because of its expansion. (When the water in the tank boils and the tank is taken out of the alcohol lamp, the remaining gas in the tank will cool and contract), so that the atmospheric pressure outside is greater than the gas pressure in the tank, and the tank is crushed. This experiment also shows the existence of atmospheric pressure.
Third, the convection of indoor air.
1. Experimental devices in textbooks. Question: Why do snakes dance? Clear: The flow direction of hot air is upward.
2. Diffusion thinking: How does the indoor air flow when air conditioning is used in winter?
Sunny: The air near the air conditioner is heated and expanded, and the density drops and rises, reaching the roof. A steady stream of hot air pushes the air in front in the upper part of the room, and at the same time, the air on the ground moves to the air conditioning place to supplement it. In this way, the air conditioner continuously heats the nearby air, forming air convection indoors, and the indoor temperature will rise.
3. Thinking: When using air conditioning in summer, which direction should the leaf fan face? Where should I put the ice cubes when selling seafood? Section 2 Composition of Air
Composition of air
(1) Determination of oxygen composition in air: 1, device diagram
2. Experimental phenomena: A. The burning of red phosphorus releases Huang Zi flame, heat and white smoke.
B. (After a while, the white smoke disappears, the equipment cools to room temperature, and then the spring clip opens. )
The water in the beaker flows back into the gas container, accounting for about 1/5 of the bottle volume.
3. Experimental conclusion: It shows that air is not a single substance; Oxygen accounts for about 1/5 of the total air volume. 4. Principle: Expression: Phosphorus (P)+Oxygen (O)? Combustion → phosphorus pentoxide P0)
Chemical equation: 4p+50- product 2P0
5. Precautions: A. Red phosphorus must be used in excess, and oxygen will not be completely consumed if it is too little.
B, wait for the gas container (device) to cool before opening the spring clip.
C, the air tightness of the device is good, (otherwise the measurement result is small),
D, first clamp the rubber tube, and then point the red phosphorus (otherwise the measurement result is too large).
Thinking: Can charcoal, sulfur and other substances be used instead? If so, what should I do?
Answer: You can't use charcoal or candles (burning produces gas, and the volume in the bottle doesn't change much), and you can't use iron (iron can't be in the air).
burn
6. The measured result in the experiment is less than the true value, which may be due to the following reasons.
A. the amount of red phosphorus is insufficient; Equipment b has poor air tightness:
C. before cooling to room temperature, open the water stop clip:
D, catheter is not filled with water in advance.
(2) Main components of air (by volume fraction):
Nitrogen (N )78%, oxygen (O )2 1% (the ratio of nitrogen to oxygen is about 4: 1),
Rare gas 0.94%, carbon dioxide (CO )0.03%, other gases and impurities 0.03%. The composition of air is mainly nitrogen and oxygen, which belong to a mixture.
Air composition nitrogen oxygen rare gas carbon dioxide other gases and impurities
Volume fraction 78% 2 1% 0.94% 0.03% 0.03%
Air composition formula: nitrogen, seven, eight, oxygen, two, one and 0.94 are dilution gases; 0.03 is second, carbon dioxide and miscellaneous gas (3) air is a valuable resource.
1, nitrogen: colorless and odorless gas, insoluble in water, does not burn or support combustion, and cannot provide breathing and chemical properties.
Not lively.
2. Rare gas: colorless and odorless gas, which can emit different colors of light after being electrified, and its chemical properties are very inactive.
Oxygen ① Animal and plant breathing medical first aid ③ Metal cutting ④ Steelmaking ⑤ Space navigation, etc.
Nitrogen ① Superconducting experimental vehicle ② Chemical raw materials ③ as protective gas ④ Food nitrogen filling as preservative, etc.
Rare gas is used as protective gas, multi-purpose electric light source, laser technology, liquid helium refrigerator and so on.
(4) Research history of air composition
1, 65438+In 1970s, Swedish scientist Scheler and British scientist chemist priestley discovered and manufactured them respectively.
Oxygen.
French scientist lavoisier first used the balance as a tool to study chemistry, and studied the composition of air with quantitative methods.
It was clearly stated for the first time that "air is composed of oxygen and nitrogen". Among them, oxygen accounts for about 1/5 of the total air volume. Section 3 Oxygen
Get oxygen in the laboratory
Laboratory preparation of oxygen (chemical change)
1, hydrogen peroxide (hydrogen peroxide) produces oxygen.
A, drugs: hydrogen peroxide (H202) and manganese dioxide (black powder MnO2) B Experimental principle:
MnO
Expression: hydrogen peroxide (H2O 2), water (H2O) and oxygen (O2)
Chemical equation: 2h2o 2·2h2o+02f
Note: MnO2 _ 2 is the catalyst of this reaction, which plays a catalytic role. C. Device: solid and liquid react without heating (hydrogen peroxide is the first type) Note:
(1) the separating funnel can be replaced by a long-necked funnel, but its lower end should be below the liquid level, so as to prevent the generated gas from leaking from the long neck.
Escape from the bucket:
② The catheter only needs to slightly extend into the test tube plug.
(3), air tightness inspection; Close it with a water stop clip, open the piston of the separating funnel, and add water to the funnel to make the water level drop discontinuously.
Explain that the air tightness is good.
(4), medicine, solid before liquid.
⑤ Advantages of the device: the start and end of the reaction can be controlled, and liquid can be added at any time. D, step: connecting, drying, charging (manganese dioxide), setting, and pouring (adding and receiving hydrogen peroxide solution).
2. Using potassium permanganate and potassium chlorate to produce oxygen.
A. drugs: potassium permanganate (deep purple solid), potassium chlorate (white solid) and manganese dioxide (black powder) B. principle:
(1) heating gas potassium acid (containing a small amount of manganese dioxide):
Expression: potassium chlorate (KCIO3)△ potassium chloride (KCIO3 oxygen (O2)
MnQ
MnO
Equation: 2kcio3д 2kcl+302 =
Note: MnO2 is the catalyst of this reaction, which plays a catalytic role in heating potassium permanganate.
Description: potassium permanganate (KMnO4), potassium permanganate (K2MnO4), manganese dioxide (MnO2) and oxygen (O2).
Equation: 2KAne4
C, device: heating solid gas (heating potassium chlorate is one kind) K2Mn04+Mn02+02 = d, operation steps: (uniformly) charging, charging, setting, ignition, collection, separation and fire extinguishing. ① Connecting device: from bottom to top, from left to right. Check the air tightness of the device: immerse one end of the catheter in the sink and hold the outer wall of the test tube by hand. If there are bubbles in the water coming out of the conduit, it is proved that the device has no leakage. After releasing the hand, a section of water column appeared at the catheter mouth.
(3) Charging: Take and use (medicine spoon or paper trough) as powder solid.
④ Fixing device: When fixing the test tube, the mouth of the test tube should be slightly inclined downward; The iron clip should be clamped in the middle and upper part of the test tube ⑤ Heating the medicine: firstly, heat the test tube evenly, and then heat the reactant part from front to back with the external flame of the alcohol lamp. 6. Collecting gas:
A, if the drainage gas collection method is used to collect gas, it will be collected when bubbles emerge evenly, and the air will just be discharged; After the water is drained, cover the bottle mouth with a glass sheet, carefully take it out of the sink and put it on the table (the density is higher than air (to prevent gas from escaping)) B. Use the upward emptying method. When collecting, the conduit should extend into the bottom of the gas container (so as to exhaust the air in the bottle).
When collecting by drainage method, put the catheter at the mouth of the gas container ⑦ first remove the catheter from the water surface.
③ Stop heating again.
E. Error-prone items:
a)。 The mouth of the test tube should be slightly inclined downward; Prevent the generated water from flowing backwards and the bottom of the test tube from breaking. The drug should be placed flat at the bottom of the test tube. b) ... When the airway is extended into the generator, the rubber plug should be slightly exposed: it is beneficial to the discharge of generated gas.
c)。 When making oxygen with potassium permanganate, plug a ball of cotton in the mouth of the test tube to prevent potassium permanganate powder from entering the airway and polluting the prepared gas and the water in the sink.
d)。 When collecting gas by exhaust method, the air duct should extend to the bottom of the gas container: it is beneficial to exhaust the air in the gas container and make the collected gas more pure.
e)。 After the experiment, first remove the airway from the water surface, and then turn off the alcohol lamp: to prevent the water in the sink from flowing backwards and the test tube from breaking. F, collection method:
Drainage method (insoluble in water)
Upward emptying method (density higher than air) G, inspection and total inspection
Inspection: put a piece of wood with sparks into the gas cylinder and find that the wood is re-ignited, indicating that it is oxygen; Full inspection: put the wooden strips with sparks on the bottle mouth. If the batten is rekindled, it proves to be full.
3 catalyst:
Concept: a substance that can change the reaction rate of other substances (accelerate or slow down) in a chemical reaction, but its chemical properties and quality have not changed before and after the reaction.
Features: two invariants (mass and chemical properties) and one change (reaction rate)
Note: ① The catalyst can't change the quality of the product and can't determine the progress of the reaction; ② The catalyst is neither a reactant nor a product.
(3) The catalyst is only used in a certain reaction, not all reactions. (4) There may be more than one catalyst in a certain reaction.
3. Manganese dioxide is not only used as a catalyst in some reactions, but also the catalyst is not necessarily only manganese dioxide. (When hydrogen peroxide solution is used to prepare oxygen, the catalyst can be copper sulfate solution, iron oxide, copper oxide and red brick powder). When potassium chlorate is used to produce oxygen, the quality and chemical properties of manganese dioxide remain unchanged, but the quality is tender and bigger. (10) Characteristics of oxygen.
I. Physical properties of oxygen
1, color, taste and state: usually, it is a colorless and odorless gas;
2. Density: Under standard conditions, the density is 1.429g/, slightly higher than that of air. (Upward venting method can be adopted) 3. Solubility: oxygen is not easily soluble in water. (can be collected by drainage),
4. Three-state change: After cooling, oxygen can become light blue liquid or even light blue snowflake solid. Second, the chemical properties of oxygen
(1) reacts with nonmetals (carbon, sulfur and phosphorus) 1 to burn charcoal (black solid).
Experimental phenomenon: in oxygen: intense combustion, emitting white light, releasing heat, generating colorless and odorless gas, which
Gas can make clear limewater turbid.
light
Description: Carbon (C)+Nitrogen (O2) Carbon dioxide (co2)
Chemical equation C+O2- 1 = CO2.
When doing charcoal burning experiment, the spoon should be slowly extended from the bottle mouth to the bottom of the bottle (make full use of oxygen in the bottle). 2, sulfur powder (light yellow) combustion:
Experimental phenomenon: in the air: a faint light blue flame is emitted; Give off heat and produce a pungent smell.
Gas.
In oxygen: give off bright blue-purple flame, give off heat, and produce gas with pungent smell.
light
Text expression sulfur (S )+ hydrogen (O2) sulfur dioxide (so2)
Chemical equation S +02= =S02
During the experiment, the bottom of the bottle should be filled with a small amount of water (to absorb sulfur dioxide and prevent air pollution). 3. Combustion of red phosphorus (dark red solid)
Experimental phenomenon: In the air: emit yellow-white flame, release heat, and produce a lot of white smoke.
In oxygen: it burns violently, giving off white light, giving off heat and producing a lot of white smoke.
light
Description: phosphorus (P )+ oxygen (O2), phosphorus pentoxide (P205)
Chemical equation: 4P+5e Product surface 2P205
Note: Phosphorus pentoxide (P205) is a solid, not a reaction between gas (II) and metals (Mg, Fe).
1, magnesium belt (silvery white solid) burns in oxygen.
Experimental phenomenon: intense combustion, dazzling white light, exothermic, white powdery solid.
light
Text expression; Magnesium (Mg )+ cyanogen gas (O2) magnesium oxide (MgO)
Chemical equation: 2Mg+02-2MgO.
Iron wire (silvery white solid) burns in oxygen.
Experimental phenomenon: intense combustion, sparks everywhere, releasing heat and generating a black solid.
light
Description: Chemical equation of iron (Fe )+ oxygen (O2)fe3o 4: JPe +202 FeJ04.
Note: 1 The iron wire must not rust; 2. The wire should be coiled into a spiral shape to increase the heating area of the wire; 3. The lower end is held by a match, and when the match is about to go out and burn out, it will extend into oxygen; 4. Spread a small amount of fine sand or add a small amount of water at the bottom of the gas container to prevent halogen substances from falling to the bottom of the bottle and causing the gas container to burst. Prevent the overflowing high-temperature melt from cracking the bottom of the bottle.
The phenomenon that iron wire can't burn in air is red heat.
(3) Reacting with certain compounds (candles, methane)-all products are; Carbon dioxide and water
Historical wind phenomenon: it is more intense than burning in the air, emitting self-light, and water droplets appear on the inner wall of the gas container, which makes the clear lime water turbid.
Produce turbid, colorless and odorless gas.
light
Description: Ishii+oxygen (O2), carbon dioxide (CO2)+ water (H20)
Burning in the air: Burning produces a yellow flame, giving off heat and slightly black smoke. (4) Reaction of other substances with oxygen
Under certain conditions, some substances react slowly with oxygen and become slowly oxidized. Slow oxidation also releases heat. Such as the metabolism of living animals, the corrosion of metals, the decay of food, the brewing of wine and vinegar, and the decomposition of farm manure.
Summary:
1, oxygen is a chemically active gas, which can react with many substances and be released under certain conditions.
A lot of heat. In these reactions, oxygen provides oxygen, called oxidation reaction. Oxygen is a common oxidant; It is oxidizing.
2. The burning degree of substances in pure oxygen is more intense than that in air. Explain the degree of combustion of substances and the concentration of oxygen.
In direct proportion:
3. When a substance burns, some will have flames, some will glow, and some will smoke. Generally speaking, gas combustion will produce flames.
Solids burn directly, producing light or Mars. The product is solid, which generally produces smoke, that is, small solid particles; 4. The reaction between substance and oxygen is not necessarily a burning phenomenon, such as slow oxidation.
Third, the use of oxygen.
(1), breathing supply: providing breathing for medical emergency patients, mountaineering, diving, aviation and aerospace; (2) Combustion-supporting: steelmaking, gas welding gas, liquid oxygen bomb and rocket combustion-supporting agent.
(4) Combustion and fire extinguishing (1) combustion
1. Concept: Flammable substances react with oxygen in the air to give off light and heat. 2. Condition: (1) flammable
(2) Oxygen (or air)
(3) The temperature reaches the ignition point (all three are indispensable, otherwise it will not burn)
As shown on the right: Turn the red brush on and off.
A, the white phosphorus on the thin copper sheet burns while the red phosphorus does not, indicating that the combustion needs the temperature to reach the ignition point;
B, the white phosphorus in the thin copper sheet burns and the white phosphorus in the water does not burn, indicating that combustion needs oxygen.
difficult position
White phosphorus has a low ignition point, so it should be stored with water in the reagent bottle of Zhong Bai Research Institute.
3. Comparison between combustion and slow oxidation
Similarities: both are oxidation reactions and exotherms;
Difference: The former reacts violently with luminescence, while the latter reacts slowly without luminescence. (2) the principles and methods of fire fighting.
1. The conditions of combustion determine the principle of fire extinguishing. As long as any condition of combustion is destroyed, the fire can be put out. 2. Fire extinguishing principle: (1) Eliminate combustible materials. (2) Isolated from oxygen (or air). (3) Reduce the temperature below the ignition point.
3. foam extinguisher: Put out fires caused by burning wood and cotton cloth.
Dry powder fire extinguisher: In addition to putting out general fires, it can also put out fires caused by electrical appliances and oil and gas combustion. Liquid carbon dioxide fire extinguisher: put out the fire of books, files, valuable equipment and precision instruments.
4. foam extinguisher's reaction principle, using sodium carbonate and concentrated hydrochloric acid rapid reaction to produce a large number of carbon dioxide to put out the fire. Chemical reaction equation: najco+2hcl-2ncl+h0hcof.
(3) explosion
Preventive measures of concept occurrence conditions
burn
A hair in which combustible substances react with oxygen.
Combustible; Use air or oxygen.
Flammable articles and other articles
The light contact with that heated and violently oxidized reaction gas; The temperature is isolated; Isolated from the air:
The ignition point lowers the temperature to the ignition point.
Combustible substances exist in a limited space.
underneath
explosion
Burning, accumulating a lot in a short time.
Heat that causes rapid expansion of gas volume and violent combustion: limited space Section IV Carbon dioxide
I. Characteristics of carbon dioxide
1, physical properties: colorless and odorless gas, denser than air, soluble in water, solid ... high pressure and low temperature dry ice 2, chemical properties:
I) Under normal circumstances, it can't burn or support combustion, and it can't supply breathing.
2) reacting with water to generate basic acid: co, +h0-h, and carbonic acid generated by co can turn purple litmus test solution red.
Carbonic acid is unstable and easy to decompose. HCo = H，O+Cot。
3) It will make the clarified limewater turbid; CO,+Ca (OH ): CaCo+H, O is used to test carbon dioxide: This is also true.
That's why there will be a white film on the wall of reagent bottle if limewater is left for a long time. In order to remove this white film, dilute hydrochloric acid is needed. Its principle is CacO +2HC! - CaC6+ H，O + Cot
4) Reaction with hot carbon: C+C0. -2co (endothermic reaction, which is both a combination reaction and a redox reaction,
Co is an oxidant and c is a reducing agent)
3. Litigation: ① Fire fighting (fire extinguisher principle: NayCO+2HCI-2NaCI+HOHCo 1) not only uses its physical properties (compactness)
Degrees greater than air), and the use of its chemical properties (can not burn, nor does it support combustion) ② Dry ice is used for artificial rainfall, and refrigerant (absorbs a lot of heat when sublimating with dry ice).
(3) greenhouse fertilizer (1) is used to make carbonated drinks (carbon dioxide is dissolved in water)
4, the impact of carbon dioxide on the environment:
(0) Excessive emissions lead to greenhouse effect.
① Causes of greenhouse effect: the energy consumed by human beings has increased sharply, and forests have been destroyed.
② Measures to reduce the greenhouse effect: reducing the burning of fossil fuels; Afforestation; Use clean energy (2, principle: react with limestone and dilute hydrochloric acid: CaCOy +2 1ICI CaCl+HOCoI.
3. Equipment diagram
Preventive measures for equipment:
(1) If hydrochloric acid is injected through a long-necked funnel, the lower end of the long-necked funnel must reach below the liquid level.
(2) If a test tube is used to hold drugs, when fixing the test tube, the mouth of the test tube is vertically upward, and the bottom of the test tube is in contact with the iron table. 4. Gas gathering method: upward exhaust method (density is greater than air, soluble in water).
5. Inspection method: Introduce the prepared gas into clear limewater, and if it can be turbid, it will be carbon dioxide.
Full inspection method: put the lighted wooden strip at the mouth of the gas container, and the wooden strip will go out. It is proved that carbon dioxide gas has been collected. 6. Industrial preparation method of carbon dioxide;
Calcined limestone: cac0, = ca0+co.
Hydrated lime can be obtained by the reaction of quicklime and water: CaO +H0Ca( OH: Section 5 Protective atmosphere).
The role of the atmosphere
Atmospheric stratification includes troposphere, stratosphere, mesosphere, ionosphere and escape layer.
What will happen to the earth without atmosphere (air)?
Focus on understanding the role of ozone layer in troposphere and stratosphere.
The role of the troposphere: it concentrates almost all the water vapor and carbon dioxide in the atmosphere, and can form clouds, rain and snow to maintain the surface.
Warm.
The role of ozone layer: ozone can absorb most of the sun's ultraviolet rays.
The use of chemicals containing chlorofluorocarbons by humans destroyed the ozone layer, resulting in an ozone hole. Therefore, the production and use of chlorofluorocarbon refrigerants and detergents should be prohibited.
Second, the greenhouse effect:
Greenhouse effect: the phenomenon that the temperature of the earth's surface rises due to the increase of greenhouse gas concentration, which makes the world warm. 1 Benefits: It is a necessary condition for human survival to ensure that the temperature on the earth is constant and suitable for biological survival.
Disadvantages: Due to the continuous development of modern industry, a lot of coal, oil and natural gas are consumed, and forests are greatly reduced, making them bigger.
There is more and more carbon dioxide in the gas, and the greenhouse effect is intensified, which makes the global temperature warm, and then affects the climate and agriculture.
The harvest of crops intensifies land desertification, leading to melting glaciers and rising sea levels, and leading to floods and inundation of cities.
Prevention and control measures: reduce the use of fossil fuels such as coal, oil and natural gas, and vigorously plant trees. Distracted thinking
Harm of greenhouse effect: 1 affecting climate and crop harvest;
(2) steam generation accelerates the temperature rise and intensifies land desertification;
Rising temperatures lead to melting glaciers, and rising sea levels lead to flooding cities.
How to control temperature and gas volume;
1 Source: reduce the burning of carbon fuels such as coal and oil, and reduce the emission of greenhouse gases such as CO2; (2) the method of removal; Plant afforestation, increase the absorption of CO2 by plants, etc.
Three. ozone hole
Mention: What are the hazards of ultraviolet rays? What is the function of smelly red layer? Let students realize the importance of ozone layer,
Title: 1982 The first ozone hole was discovered over Antarctica, and it was still expanding by 1992. Some videos and pictures about the ozone hole are inserted, so that students can clearly understand the ozone hole (the ozone concentration in the ozone layer is obviously reduced) and its formation reasons (chemicals such as chlorofluorocarbons and oxides are emitted by human activities).
Extended activities (surfing the Internet, etc.). ): (1 Are there any other ozone holes besides the Antarctic ozone hole? (2) What role did fluorocarbon and other substances play in ozone conversion?