Several science questions for the second year of junior high school, science questions for the secon

1.Help me determine whether several plants have straight or fibrous roots:

Garlic fibrous roots, spinach straight roots, soybean fibrous roots, 2"Indoors**, don't rush to open the skylight"Is this right or wrong?

That's right, opening the skylight is like installing a chimney, and the burning will be more intense.

3.Chlorine gas is yellow-green, is it true that chlorine atoms are also yellow-green?

No. 4.Do you need to fertilize the plants when transplanting, do you need to water a lot of water?

No fertilization is required, but a lot of water is generally required.

5.The following statements about soil resources are incorrect.

a. The soil does not need to be fertilized after burning the crop straw b. Burning the mountain will lead to a decrease in soil fertility A The soil also needs to be fertilized after burning the crop straw, because the crop straw only contains a part of organic fertilizer and a small amount of inorganic fertilizer.

Why?

Garlic fibrous roots, spinach straight roots, soybean fibrous roots, 2"Indoors**, don't rush to open the skylight"Is this right or wrong? Right.

3.Chlorine gas is yellow-green, is it true that chlorine atoms are also yellow-green? Wrong.

4.Do you need to fertilize the plants when transplanting, do you need to water a lot of water? Use.

5.The following statements about soil resources are incorrect.

a. The soil does not need to be fertilized after the crop is burned.

1 Spinach: fibrous root system Soybeans: straight root system.

2 Because of the three elements of combustion: combustibles, ignition points, oxygen.

If you are indoors**, open the windows immediately and the air will circulate, the oxygen content will increase, and the fire will burn more vigorously.

1. The total mass of a glass bottle with a mass of kilograms is weighed as kilograms when filled with water, so the mass of the water is kilograms, divided by the density of water, and the volume is cubic decimeters. When filled with a certain liquid, the total mass is weighed in kilograms, minus the weight of the bottle is kilograms, and the mass of the liquid is kilograms. Divide by the volume of the liquid (i.e., the volume of the bottle in cubic decimeters), so the density is multiplied by ten cubic kilograms per cubic meter.

If the volume is cubic decimeter, the density is multiplied by ten to the third power.

1. Because the buoyancy is greater than the gravity, it will float.

2. All are suspended, because the density of the object = the density of the liquid when suspended, the density is the characteristic of the substance and will not change, so it is still suspended.

One is to use a small rigid bar to close a ferrous metal object to see if there is a gravitational force.

Second, use a small rigid bar to approach the compass to see if the compass is deflected.

The more water dissolves the more salt, so the content of soluble salts in the soil is very high, and the solution is not easy to become a saturated solution.

Anhydrous copper sulfate powder is a solute, so if it is added to the saturated solution, it will be combined with water to form copper sulfate pentahydrate, which is a crystal, and each copper sulfate molecule takes away 5 water molecules, so the solvent is reduced, the relative dissolved solute is less, and the quality of the whole solution is also less

Assuming that the mass of the object is m, the volume is v, and the density of water is p water, then mg = p water * 3 5 * v * g gives p matter = m v = p water * 3 5 = kilogram cubic meters.

The buoyancy of water is vg=20n

v=2×10－³

The volume of the metal ball is 2 10 m

m v= so it should be aluminum.

Volume is: cubic meters.

A metal with a density of 2700kg cubic meters.

--Mass of 20 ml of properacetic acid solution:

Mass * volume = grams of centimeters of cubic * 20 ml * 1 centimeter of cubic milliliters = 23 grams of 20 milliliters of peracetic acid proto-solution containing peracetic acid:

Mass * concentration = 23 g * 15% = g.

20 ml of peracetic acid probiotic acid solution containing the mass of peracetic acid is in grams depending on the dilution process.

The mass fraction of peracetic acid in 100 ml of peracetic acid solution containing peracetic acid is also grams, so in the prepared 100 ml of peracetic acid solution, the mass fraction of peracetic acid is:

g 100 ml * 1 ml cm to the power = g cm to the third power.

1.Ships far from the coast seem to be constantly sinking.

Answer: This illustrates that the Earth is round, but it does not illustrate that the Earth rotates.

2.Objects that fall from a height will inevitably fall to the east.

Answer: This question is wrong, it is from the west and not from the east.

The current direction of rotation causes the landing site to be westerly; If it goes east, the Earth rotates in the opposite direction.

3.Tidal phenomena in the Qiantang River.

Answer: This is caused by the rotation of the Earth.

Reason: Because of the rotation of the earth, the water on the surface of the earth is not a rigid body with the surface of the earth, and the seawater on the surface cannot maintain the same rotation speed as the earth, but lags behind the rotation speed of the earth.

On the other hand, due to gravitational pull, the sea surface facing the Moon will ** and the sea level on both sides of the Earth will fall.

Since the overall rotation speed of seawater cannot keep up with the earth's crust, periodic ebb and flow are formed.

4.The degree of wear and tear of the rails on both sides of the railway tends to be different.

A: This is also a result of the rotation of the Earth.

Because of the rotation of the earth, the ground objects follow the earth in a circular motion. With the exception of the equator, the circular motion of objects in other regions is not centered on the sphere of the Earth, but on the points on the Earth's axis. Since the further to the poles, the radius of the circular motion is smaller.

The gravitational force of an object is perpendicular to the ground, and the component of gravity in the direction perpendicular to the Earth's axis provides the centripetal force required for the object to rotate with the Earth on the ground. The north and south sides of an object, because the distance from the earth's axis is different, the centripetal force required is not the same, so the friction force of the train acting on the north and south rails is not used, and the wear is different.

If the landlord still has questions, please come and discuss.

1 Explain that the earth is round.

2 is not going to happen.

3 is caused by the gravitational pull of the Moon.

4 Uncertainty Principle??

24 should be chosen, because the earth rotates, the northern hemisphere and the southern hemisphere are different, the south clockwise and north counterclockwise, so the northern hemisphere's high-altitude falling objects will be biased eastward, and the degree of wear and tear of the rails on both sides of the railway is often different.

1 is the rotation of the moon caused by the difference between the position of the earth and the moon.

1 Visually near and far small, it may indicate that the earth is round.

2 This is related to geostrophic deflection forces in high school geography and is related to air friction in the northern and southern hemispheres.

3 This is different from the gravitational attraction between the earth and the moon and the sun, because the earth rotates, so the gravitational force is different, so there is a tidal phenomenon.

4. Isn't this one of the manifestations of the Earth's rotation?

B electric fan blows air on the wing, the air flow above is fast, the pressure is small, and an upward lift is generated, the indicator of dynamometer B below increases, and the indicator of dynamometer A above the wing model decreases. The higher the flow velocity in the fluid, the lower the pressure.

It is equivalent to 60 grams of water dissolving 30 grams of potassium nitrate to form a saturated solution, and the solubility is 30 60 100 = 50 grams of 100 grams of water.

The mass of oxygen is.

The amount of metallic substance:

Amount of oxygen substance:

Therefore, the modified oxide is M3O4

The relative atomic mass of the metal is 56, for, these metals are all derived from oxides, , is the mass of o in the oxide, and the formula of o is 16, so there are o atoms that are, and the oxide contains the metal at the same time, contains oxygen, obviously, its chemical formula is:

m3o4

Solution: The number of moles of a metal is.

The mass of o in the metal oxide is.

So the number of moles of oxygen is.

Therefore, the ratio of the number of metal elements to oxygen elements is 3:4

So the oxide is M3O4