Urgent!!!!! Summary of the key points of science from the first to the second year of junior high sc

You want to summarize the key knowledge of the subjects from the first to the second year of junior high school.

Pressure f = sled gravity g = 1960n

Pressure p = pressure f contact area stuffy base s = 1960 maximum pressure p = maximum pressure n area s, n = p · s = 7000000 · maximum loading gravity g'= maximum pressure n - sled gravity g = 14000-1960 = 12040n

First, find out how much solvent is in 200g of potassium nitrate saturated solution at 20°C.

200：x=（100+：100

x = 152 grams.

Solubility y = 200-152 = 48 grams.

When the temperature is raised to 60 °C, the mass of potassium nitrate that can be contained in 152 grams of solvent m: 152 = 110: 100

m=167, the amount of potassium nitrate that should be added is.

n=167-48=119

Therefore, 119 grams of potassium nitrate need to be added.

1.Water 2The content of inorganic salts is high.

3.Inorganic salt.

4.Reduces the respiration of crops and reduces the consumption of organic matter.

5.At this time, there is more organic matter in the crop, which can be used for respiration for a longer time, and the probability of survival is greater.

Hope it helps.

All of the above topics that you are talking about word by word, and then play praise for having a strong desire to learn?? Children who are eager to learn. 。

Shall I help you? Dispel doubts.

The first known S (Note Unit) of F-P is also known directly by the formula P=FP=*10-6

m = density * v gasoline mass and mass total empty barrel can be approximated as a 20kg relation, r = 200 ohms i = u r =

Should almost be able to pick a bone in the egg, then it is unforgettable for the baby's hard work to survive in my style for years to come. 。

I'm also in the second year of junior high school, your topic is not difficult, ** question is better to do it yourself.

(1) After evaporation, 20g of potassium nitrate is obtained, indicating that the solute mass in the original solution is 20g mass fraction = (solute mass solution mass) * 100% substitution value (20 50) * 100% = 40%.

2) The dilution of the original solution is called a solution with a mass fraction of 10%, that is, the mass of the solute remains unchanged, how much solvent is added to change the mass fraction of the original solution to 10%, if you need to add water x grams, 10%=(20 (50+x)))*100%, you need to add 150g of water to get x=150g

1. Hydrogen gas is ignited, and a beaker is buckled on top of the flame to see if there are water droplets generated.

2. Copper chloride, hydrochloric acid There is a precipitation of red substance, and bubbles appear on the surface of the iron rod.