How do we know a chemical reaction has taken place?

How the chemical reaction takes place?

Do you think that a chemical reaction has taken place in the flask ? Give reason.

Do you think that a chemical reaction has taken place in the flask? Give reasons. Do the weights of the flask and its contents change during activity?

How do you write a chemical equation?

how do you write a chemical equation?

How does chemical coordination take place in animals?

a) What is chemical decomposition reaction? b) In what conditions chemical decomposition reactions takes place ? Explain various condition.

How do we know that it (Fe) has changed?

How do we know that we need food ?

How do we kill microbes?