Science-My Reflection: Chemical Changes

Well, we started off with a new topic, Chemical Changes, today. There are many concepts in this chapter that are very complicated. But after this lesson, I managed to get a better understanding on what the topic is all about and remember most of the concepts and ideas being taught to us.

3 Thoughts:
1) A chemical change is permanent where new substance is formed. The change is usually irreversible and a chemical reaction will always take place. A chemical reaction is a process whereby reactants (substances that are used for the reaction) are changed into new substances, also known as, products (substances formed). In addition, during a chemical reaction, no substances are destroyed or created. The atoms in them only re-arranged themselves so as to form new products.
2) A chemical reaction can be represented using equation. The equation can be written using words (word equation) or chemical formulae (chemical equation). Information on identity of reactants and the final products using chemical formulae and possible reaction conditions (e.g. temperature, physical state, etc.) are provided in a typical chemical equation. We can only say about the quantities involved in a chemical reaction when the equation is balanced. By balancing a chemical equation, we have to place numbers in front of the formulae of the substances in the equation.
3) There are four types of interactions which involve in chemical reaction. The four types are:

Interaction between matter and heat (E.g. Combustion, Combination and Thermal Decomposition)
Interaction between matter and light (E.g. Photosynthesis and Photography)
Interaction between matter and electricity (E.g. Electrolysis)
Interaction between matter and another matter (E.g. Digestion, Neutralization and Rusting)

2 Questions:
1) Why electrolysis can also be a physical change?
2) When there is a plus (+) sign at the left hand side of the chemical equation, then can it be eliminated from the right hand side? Or must the plus (+) sign still remains on the right side?

1 Useful application:
1) Chemical changes help us understand more about the things happening to us in our daily lives and we are also able to know what are the changes and interactions that are going on around us.