PHYSICAL AND CHEMICAL CHANGE
PHYSICAL AND CHEMICAL CHANGE
A chemical change occurs when one or several pure substances turn into different pure subtances. This chemical properties of a substances determinate its abilty to transform into other substances.
The original substances that undergo a change or a chemical reaction are called
The substances that result from a change or a chemical reaction are called the
Types of Chemical Reactions
In a decomposition reaction, a reactant generates or decomposes into two or more products.
In a synthesis reaction, two or more reagents are combined to generate or synthesize a product.
In a substitution reaction, two or more reactents turn into two or more products.
Identifying chemical changes
The substances give off diffetent
When we notice changes in smell, we can say that the food has undergone a chemical change.
The newly formed substances have a same temperature, a
state of aggregation
different than the state of aggregation of the original ones.
When gases form in a substance, which has not reached its boiling point, it means that it is undergoing a chemical change.
The mixture of substances with different states of aggregation is due to the fact that the resulting substances and the original substances have different melting and boiling points.
Some chermical change are linked to noticeable changes in
Some chemical changes occur accompanied by a loss or emission of heat that is greater than those produced in physical changes.
Combustion: a type of chemical change characterized by an intense release of heat and light.
The subtances have a different
If a substance changes color, it means that it undergoes a chemical change. But this does not necessarily mean that all chemical changes involve a change of color.
: it is a chemical change that implies an alteration in the color of the original substances.
Reverting a physical change means getting back the physical properties of the objects that underwent the change.
Reverting a chemical change means recovering the original substances.
In general, chemical changes are very
dificult to reverse,
harder than physical ones.
The phenomenon of
expansion and contraction or deformation
, that is the
change of state,
is physical. It usually happens when you heat or freeze a substance.
Physical change has physical properties, such as density and viscosity. It depends on the temperature of the object that has some properties or other ones.
Physical properties are broadly classified into 5 groups:
How an object or material behaves when forces are applied to it. Fragility, elasticity, malleability, and hardness are but a few examples.
The behavior of materials when subjected to an electric current. Electric condutivity is one of the most important of the electrical properties.
The properties of objects and materials taht are capable of generating magnetic forces or interacting with them.
The behavior of a material when subjected to heat. Some examples include thermal conductivity. Menting point, and boiling point.
The behavior of materials when subjected to light. Two example are transparency and color.