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Curd, lemon juice, orange juice and vinegar taste sour. These substances taste sour because they contain acids. The chemical nature of such substances is acidic. The word acid comes from the Latin word acere which means sour.
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I am confused as to what you're asking.
The answer is Electrons move between objects. The reason this is known is that the acts of friction and conduction (from the little picture he could not put in) involves contact to be known as friction and conduction. Without contact the electrons could not move between objects. I also got this question right on the test. That's how I know this is right. I hope this helps. ( ͡° ͜ʖ ͡°)
A, because the number of valence shell electrons (outer shell electrons) tells us how much the element or compound wants to bond or give up electrons. Most compounds and elements want to have eight valence ectrons in it's outer ring. So if an atom is far away from having eight, it will want to react more often.