Answer:
The answer to your question is below
Explanation:
Covalent bonds are bonds between to atoms that share a pair of electrons, there are three kinds of covalent bonds but I'll describe only two:
Covalent non polar bond: is a covalent bond between two elements of the same element. Ex two hydrogens, two chlorine, two oxygenes, etc.
Covalent polar bond: is a covalent bond between 2 elements of different elements, for example: hydrogen and chlorine or nitrogen, they are polar because on of the element that form it is smaller than the other one, then a partial positive and a partial negative charge is formed.
Respiring while swimming underwater
Because anaerobic respiration means respiration with no oxygen, and there is no oxygen underwater
Answer: The kilograms of water must evaporate from 8kg of a 25% salt solution to produce 40% salt solution is 3 kg.
Explanation:
According to the ratio and proportion:

where,
= concentration of ist solution = 25%
= mass of ist solution = 8 kg
= concentration of second solution = 40%
= mass of second solution = ? kg


Thus the final solution must have a mass of 5 kg , i.e (8-5)= 3 kg of mass must be evaporated.
Therefore, the mass that must be evaporated from 8kg of a 25% salt solution to produce 40% salt solution is 3 kg.
Yes, it is true that ions can have a positive or negative charge.