A chemical reaction is a process in which one or more chemicals
(or things) combine to make something new. The ‘things’ or chemicals that we
started with are called Reactants and the new ‘thing’ that is made are called
Products. It is called a chemical reaction since:
- It is accompanied by a rearrangement of the
atoms in the reactants to form different chemical matter. The product formed is
a new entity and is chemically different from the starting reactants. - It is usually irreversible: this means that in
most cases, I cannot get back what I started with. - A chemical reaction is usually accompanied by
a color change, smell, heat or light or release of a gas.
An example
of chemical reactions is the burning of wood in the presence of oxygen to
produce ash, water vapor and carbon dioxide.
A Chemical reaction or change is different from a physical change.
A physical change usually involves only a change of state: from
solid to liquid, liquid to gas or gas to water. A physical change does not
involve a change in the chemical entity of the reactant. The products will have
different physical properties than the reactants (such as state of matter,
texture, shape), but the chemical structure remains exactly the same as the
reactants. Therefore, a physical change is usually reversible.
An example
of a physical change is the change of states of water. Liquid water freezes to
become ice, and when heated turns to water vapor or steam. But in all three
states, it is still chemically identical: H2O, which is made of two
atoms of Hydrogen and one atom of Oxygen. So, change of states of matter is not
a chemical, but a physical change.
In the Bang
in a Bag chemical reaction you just observed, acidic vinegar (chemically acetic
acid) reacts with basic baking soda (chemically sodium bicarbonate) to form an
entirely new substance called sodium acetate, carbon dioxide (the gas produced)
and water. Once the reaction is complete, you cannot get back the vinegar and
baking soda. The release of carbon dioxide caused the sound and the bubbling
you observed during the chemical reaction.
Join our HTHT @ Home Science Experiment and make your own Bang in a Bag:
https://sciencemadefun.net/downloads/Bang%20in%20a%20Bag_EOTD_May%2012th.pdf