Answer:
21. Erosion causes physical changes. For example - Land degradation, deforestation.
20. B statement is closely related to climate.
hope it helps!
.86km is the correct answer
The answer is A. Table salt is a pure substance.
Answer:
order = SrS > SrCl2 > RbCl > CsBr
Explanation:
Comparison of the melting points of compounds is basically dependent on the charge on their cation and anion, the more the charges on the cation and anion, the stronger and greater the force of attraction and as such the melting point will be relatively higher as well.
The ionic radii is also another factor to be considered, the more the distance between ions, the lesser the bond strength and the lesser the melting point.
from the options, in terms of ionic radii SrS > SrCl2 and RbCl > CsBr
also both SrS and SrCl2 have more charges on their ions compared to RbCl and CsBr and as such the arrangement of the highest melting point will be in the order SrS > SrCl2 > RbCl > CsBr.
Answer : The final temperature of the mixture is 
Explanation :
In this problem we assumed that heat given by the hot body is equal to the heat taken by the cold body.
where,
= specific heat of iron = 
= specific heat of water = 
= mass of iron = 39.9 g
= mass of water = 
= final temperature of mixture = ?
= initial temperature of iron = 
= initial temperature of water = 
Now put all the given values in the above formula, we get
Therefore, the final temperature of the mixture is
