A few science questions, everyone help Thank you

The heat emitted by sand is the same as the heat absorbed by water, and the mixing temperature is less than 30 The same heat absorption and heat is the same, and the specific heat of water is larger, that is to say, the heat absorbed by one degree of elevation is more than the heat emitted by sand. If the water is not mixed, the heat absorbed by the water from 20 degrees to 30 degrees is completely provided by the sand, and the sand must be reduced from 40 degrees to below 30 degrees, so the mixing temperature must be lower than 30 degrees.

6.Left. When the ice melts, it is necessary to absorb heat, the surrounding temperature decreases, and the water vapor in the air condenses into small water droplets, which adhere to the paper, so.

The Iceman lies, because the lowest zero degrees are less than -1000 degrees, only Celsius.

300,000 m s is the same as the speed of light.

The answer is as follows: d, the specific heat of water is larger, so it will be lower than 30 degrees, and the heat absorbed and released are of course the same, and the heat is conserved!

The scales are tilted towards the ice, because the ice is cold, which will liquefy the water in the air, causing more water to reach the ice.

The Iceman lied, because the lowest zero degree was less than -1000 degrees, and it seemed to be just over 300.

c The specific heat capacity of water is greater than that of sand, and the heat contained by sand at the same temperature is much more.

Left, there is water vapor in the air, and the water vapor that is very close to tissue paper or even in contact with it becomes water droplets due to liquefaction.

The Iceman lied, and the absolute zero in the universe is only degrees Celsius.

300,000 m s

The wrong thing to do is: 1 Spit out the phlegm under your desk 2 Wipe the phlegm off with the sole of your shoe The reason why you can't do this is: Xiaohua's phlegm.

There are many germs in it, which are the bane of spreading diseases. People think of phlegm as "garbage" for breathing, which is a very apt metaphor.

What's more, Xiaohua is a patient who is catching a cold, and the sputum he spits out contains more bacteria and viruses. If the patient spits the sputum on the ground, the bacteria will fly around with the dust when the sputum dries. In places where spitting, everyone has the opportunity to inhale pathogenic bacteria. The correct way to do this is to spit it in a tissue and throw it in the trash.

That's the answer, oh, really.

He spat out the phlegm under his desk, which should have been wrapped in tissue paper.

First NaCl solution, agCl can be precipitated

With the addition of NaOH solution, Cu(OH)2 can be precipitated, and finally by adding Na2CO3 solution, BaCO3Cl:AG can be precipitated.

NO3: All soluble.

CO3: BA, CA, AG are insoluble.

OH: Except for K, NA, BA, CA, they are insoluble.

(1) Use a knife to dig a round lid on the top of the pumpkin, then remove the top lid and clean the inside of the pumpkin with a spoon.

2) Place the candle inside the pumpkin and light the candle.

3) If the top of the pumpkin is re-closed, will the candle continue to burn? Why? The candle will go out soon because the oxygen is isolated.

4) Use a knife to dig a hollow nose on the outside of the jack-o-lantern, light the candle, and then put the top lid on, and it won't take long for the candle to go out again, why is that? Because the volume of carbon dioxide gas produced by the burning of the candle is stored below the "hollow nose", when the height of the candle flame is lower than the height below the nose, the accumulated carbon dioxide gas extinguishes the flame.

5) Use a knife to dig another hollow mouth for the jack-o'-lantern, light the candle, and then close the top lid again, this time, the candle will continue to burn.

6) Extinguish the candle, then dig a pair of hollow eyes in the jack-o'-lantern, light the candle again, and close the top lid.

7) Light two matches and extinguish the flame on the match, at this time the match is still smoking, and then immediately move the two matches to the mouth and eyes of the jack-o-lantern respectively, the smoke from the mouth will be inhaled, and the smoke by the eyes will be blown outward. (Because the flame inside the pumpkin is still burning, the heated air inside rises, but because the "lid" is closed, the hot air can only flow outward from the "eye" at the top, and the cold air can only flow into the pumpkin from the cooler "mouth" to replenish it, and the smoke from the freshly extinguished match indicates the direction in which the air enters and exits the inside of the pumpkin).

The volume of seawater that is discharged when a mine is submerged in water.

v row = v = then the buoyancy experienced by the submerged in the water.

F float = p seawater v discharge g = 1020kg m *

Because the f float is greater than g

So float up and eventually float on the water.

No you can clap your hands in front of him and see if it changes the direction of movement.

is wrong. If the two poles in solution A are close together, it is equivalent to shortening the length of the resistance of A, the resistance becomes smaller, and B remains the same, and the circuit current becomes larger, so U2 becomes larger.

b False. Adding a small amount of Ba(OH)2 can react with part of H2SO4 to form BaSO4 (precipitation) and H2O, the solution ions are reduced, the conductivity becomes weaker (that is, the resistance is equivalent to an increase), the resistance of B becomes larger, the other resistance of the circuit remains unchanged, and the partial voltage of B resistance increases, so U2 increases.

c Right. At the beginning, such as B, the total current decreases, until the amount added is exactly the complete reaction with sulfuric acid, A solution is actually water and precipitation, the middle school water does not conduct electricity, the circuit is broken, and the bulb will dim until it is not bright; Continue to add barium hydroxide A will become a barium hydroxide solution, and there are ions, the conductivity of the solution will gradually increase, the current will gradually increase, and the bulb will become brighter.

d False. Conductive because dilute sulfuric acid ionizes hydrogen ions and sulfate ions, making the solution conductive, not ionizing sulfuric acid.

A is wrong, "because the potential difference between the two poles in solution A has nothing to do with the distance between the two poles, but with the concentration of the solution or the strength of the ionization of the electrolyte!" ”

d I think it's wrong, whether there is electricity or not, dilute sulfuric acid is ionized.