How do you know the valence of a non-metal?

How do you know the valence of a metal?

How do you know the reactivity of metals with chlorine decreases from top to bottom?

How do you know the nature of salt formed due to the reaction between acids and bases?

How do you know the percolation rate of soil?

How do you separate small pieces of metal in the engine oil of a car?

How do we know that we need food ?

How do you know that rusting of iron is a change? If a raw egg is boiled in water, what changes do you notice in it ? Explain.

How do you know that rusting of iron is a change? If you are given two eggs, can you determine which one is boiled and which one is not ? Explain.

Do you know to catch fish in pond?