A few science questions in the first year of junior high school! About vaporization and liquefaction

1.Elevated; unchanged (water absorbs heat but does not heat up when boiling); Stop it; Suck.

2.The bag starts to swell because the boiling point of the alcohol is about 80 degrees, and the alcohol boils when you put the bag in hot water.

3.Because the heat absorbed by the paper is absorbed by the water, the temperature of the paper can only reach 100 degrees Celsius even when it is boiling, so the temperature of the paper can only reach 100 degrees at most, so it will not burn.

1.Elevated; No change; Stop it; Absorb.

2.The liquid alcohol has become vapor. After a while, it changes back to a liquid state.

3.The water wets the carton and absorbs the heat.

Elevate unchanged stop suction continuously.

What does the second question mean?

3.Water absorbs most of the heat, so that the temperature of the paper is about the same as the temperature of water, and the boiling point of water is 100 degrees Celsius, so the temperature of the paper does not reach its ignition point.

1. Rise, remain unchanged (the boiling point of water is 100 degrees), stop, suck.

2. The plastic bag begins to expand, because the boiling point of alcohol is about 80 degrees, put the bag into hot water above 80 degrees, and the alcohol will boil.

3. Because the temperature of the paper does not reach the ignition point. Reason: Liquid water can only reach 100 degrees when it boils, and it needs to absorb heat continuously, so the temperature of the paper can only reach 100 degrees at most, and it will not burn.

1.Observing the process of water boiling, it can be concluded that before the water boils, the water is heated, and the temperature of the water rises.

The bag bulged and the liquid was gone. The bag deflated again.

Alcohol has a low boiling point and is endothermic vaporized in hot water. Gaseous alcohol liquefies when cold.

3.When the water boils, it continues to absorb heat, and the temperature of the paper will not continue to rise, and it will not reach the ignition point, so it cannot be burned.

Vaporization: Evaporation: less water in the river, less water in the bottle, less alcohol, rubbing alcohol to cool down when you have a fever, wiping your forehead with a wet towel to cool down, shivering cold just after swimming, the dew is gone soon after the sun comes out, the grain is dried, wet clothes are dried in summer, hair is dried, the salt works use seawater to dry salt, the cold winter just enters the warm room from the outside, and the comrades who wear glasses know that there will be a layer of fog on the lenses, and it will be gone after a while, and the process of disappearance is evaporation.

Boiling: The water in the kettle is almost boiled dry, liquefaction: the cold winter has just entered the warm room from the outside, and comrades with glasses know that a layer of fog will appear on the lenses, the formation of fog, the formation of hot gas, the breath to the hands, the warming of the hands, the formation of clouds, the formation of dew,

Vaporization (evaporation): 1The river becomes less watery.

2.There is less water in the bottle.

3.If you have a fever, rub it with alcohol to cool down, and wipe your forehead with a wet towel to cool down.

4.Just after swimming, I just got ashore and shivered coldly.

5.Soon after the sun came out, the dew was gone, and the grain dried.

6.Wet clothes dry out in the summer.

7.Hair is blow-dry.

8.The salt works use seawater to dry salt.

Liquefaction: 1As soon as the cold winter enters the warm interior from outside, a layer of fog appears on the lenses.

2.Fog formation. I breathed into my hands, and my hands became moist and warm.

3.The formation of dew.

One. 1。Absorption is elevated 2.

Absorption unchanged small 3If it does not change, the sail swims heated 1At a certain temperature the internal surface 2

When the saturated vapor pressure is equal to the outside pressure 1Different 100 II. 1。

Gaseous liquid release 2. Reduce the temperature and increase the high pressure strongly 3Oxygen cylinders in hospitals, liquefied acetylene in factories, liquefied ammonia.

Class Summary: One. Reach the boiling point and continue to heat II.

Same: Both are gasification phenomena, and they all have to absorb heat. Different:

Evaporation takes place on the surface of a liquid. Boiling the surface and inside are carried out together III. Gaseous liquid Sun pin state Lower temperature Raise high temperature car attitude Knowledge application:

Liquefaction releases.

1.Fog of water vapor condensation (water vaporization into water vapor, which adheres to tiny substances in the air, forming a fog).

2.Rain formed by cloud droplets (water first vaporizes into water vapor, water vapor liquefies into water or condenses Xiaoice crystals when cold in the air, and then falls, and Xiaoice crystals may also melt into water and become rain when they fall).

3.Snow formed by ice crystals (water first vaporizes into water vapor, and the water vapor condenses in the air to form Xiaoice crystals, and then falls, turning into snow, i.e. hail).

4.Hail (water first vaporizes into water vapor, which condenses into Xiaoice crystals in the air, and then falls and becomes hail, i.e. snow).

Dew condensed on the ground (water vaporizes into water vapor, and water vapor liquefies into dew when cold).

There are two ways of liquid vaporization: evaporation and boiling, evaporation is a slow vaporization phenomenon that occurs on the surface of a liquid, and boiling is a violent vaporization phenomenon that occurs on the surface and inside of a liquid at the same time

So the answer is: evaporation; Boil

1.The purpose of this experiment is to study the relationship between the speed of evaporation and the liquid (surface area), and when doing this experiment, it can be found that the alcohol in the bottle with a large diameter evaporates (fast) than the alcohol in the bottle with a small diameter (optionally "fast" or "slow"), this experiment shows that (the surface area of the liquid is large, the evaporation is faster; Conversely, if the liquid surface area is small, the evaporation is slower).

2.Xiao Shen finished swimming and came up from the pool to feel cold. Please imagine the general situation of Xiao Shen at that time, feel and analyze the reasons for "cold".

Answer; The water on the body is evaporated, and after coming up from the pool, because the body is full of water, because there is air flow, the water will be evaporated, and the vaporization will absorb heat, and the heat on the body will be sucked away, and it will naturally feel cold.

Please cite again. 2. Three similar examples from life.

For example; After taking a shower, especially in winter, you will feel cold before you wipe your body. (Vaporization and endothermy).

Vaporization, liquefaction, boiling.

1.When the water is boiled, the water vapor escapes from the spout mouth, the water vapor is invisible, the water vapor meets the cold air, it will condense into small water droplets, and the "white gas" that you usually see is these small water droplets, not the gaseous water vapor, and the glass can receive water droplets formed by small water droplets, which shows that (water is first heated and vaporized and then liquefied in cold).

2.In summer, there are many small water droplets on the outer wall of the box containing frozen drinks, which are made (liquefied and exothermic).

3.Take a piece of paper and fold it into a carton, fill the carton with an appropriate amount of water, and heat it with an alcohol lamp until the water boils, but the carton is intact, think about it, why is that? Answer; Because there's water in the paper, the temperature of the paper is going to be low, despite the fire.

Study physics well, and now you can't think that the hard things are ahead.

1 Surface Area Fast All other things being equal, the larger the surface area of the liquid, the faster it evaporates.

2 The evaporation of water in the body takes away a lot of heat, so it is cold Example Rub alcohol to cool down when you have a fever1 Water is first heated and vaporized and then liquefied when it is cold.

2. Water vapor liquefies when cold.

3. Water vaporization takes away a lot of heat and cannot reach the ignition point of the paper.

The surface area is fast and the temperature and air flow are the same, the larger the surface area of the liquid, the faster the evaporation.

Evaporation area Fast The speed of evaporation is related to the evaporation area of the liquid, the larger the area, the faster the evaporation, and vice versa.

1 Surface area fast All else being equal, the larger the surface area, the faster the evaporation.

2. Evaporation absorbs heat Extinguish the fire with water In summer, it is cool to wipe your face with a wet towel.

3. The temperature of glass is low and the boiling point of water vaporization is 100 degrees, while the ignition point of paper is greater than 100 degrees.

2010-3-19 16:07 liuxuanhui11 |Level 2.

1.In real life, when you lift the lid of a pot of boiling water, you can see that water is dripping from the lid of the pot, and this water is formed by the steam of boiling water.

2.and can liquefy gases, some gases cannot be liquefied by compression alone at room temperature, and must be made to manage to liquefy them.

Water vapor scalds the human body are more severe than 100t water scalds the human body due to

4.The biggest advantage of liquefiing the gas is that it is convenient for the hydrogen used as fuel and the oxygen used as an accelerant in the Long March 3 rocket developed by China to be loaded into the rocket.

5.LPG is used to fill LPG in steel tanks.

6.The following statement about the refrigerator when it is working is true: (

a. Refrigerators are cooled by absorbing heat when Freon or other substances are melted.

b.The vaporized gas is liquefied into a liquid in a condenser and absorbs heat.

c.The liquefied liquid flows back into the tubes in the freezer chamber to vaporize and release heat.

d.Freon leaks in refrigerators pose a threat to the planet's ecology.

7.The boiling points of oxygen, nitrogen, and ammonia are known to be: -183, -196, and -335 respectively

a.Ammonia, oxygen, nitrogen bNitrogen, oxygen, ammonia cNitrogen and oxygen do not liquefy dAmmonia does not liquefy.

8.When steaming steamed buns in a multi-layer steamer, the first to cook is: (

a.Upper bMiddle layer CLower dAll layers at the same time.

9.One of the following liquefaction phenomena differs from the other three liquefaction phenomena: (

a.Fog formation.

b.In winter, we will see the "white gas" that we exhale

c.In the morning, we sometimes see dewdrops attached to the plants.

d.In summer, we often see water pipes "sweating".

Question paper answers: 1 Exothermic liquefaction of a cold pot lid 2 Lowering the temperature Compressing the volume The temperature drops below a certain temperature 3 A large amount of enthusiasm is released when the water vapor liquefies into water 4 The volume becomes smaller Storage and transportation Liquid 5 Normal temperature Compressing volume Liquefaction 6 9 d c a b

Declare in advance that it's wrong, don't blame me.

Vaporization absorbs any vaporization.

ADBCB A Methyl Thermometer Decreases.

The air flow on the surface of the liquid is faster, and the faster the substance vaporizes, the more heat is absorbed.

Rise Fall Rise gradually.

Vaporization Vaporization.

A: It makes sense, because sweat vaporization has to absorb a lot of heat from the human body, and then being blown by the wind will make you feel cold and easy to catch a cold.

A: Increasing the surface area of the liquid and speeding up the flow of air on the liquid surface makes the hair dry faster.

2 1 I won't write the next question.

Reducing the temperature Compressing the volume Liquid Gaseous Absorption Certain Alcohol lamp does not need to absorb heat for water boiling d

Water vapor is exothermic when cooled.

17 98 does not absorb a certain temperature.

Water and oil vaporization.

Xiao Li: If the water continues to heat after boiling, it will not increase the temperature of the water, because the boiling point of water is 100

Observe if the water will vaporize from large to small, from small to large.

b Next stop fighting, tired to death.