A Chemical Change is any change that results in the formation of new chemical substances. A Physical Changes are changes affecting the form of a chemical substance. A Physical Property is any property that is measurable whose value describes a state of a physical system. A Chemical Property is any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity.
Why Do We Like Physical and Chemical Changes
We like physical changes because they are
important. The importance of a physical change is it ends up the same material
as an outcome. For example if you rip paper into pieces it is a physical change
because it is still paper. A chemical change is when some thing changes into
another energy or substance. For example if you burn wood the wood is changed
into heat and light energy. Without the burning of wood there wouldn’t be any
heat or light. They’re important tom everyday life. When a tree catches on fire
that’s a chemical change because the trees wood is changing.
Summary All substances have
properties that we can use to identify them. For example we can identify a
person by their face, their voice, height, finger prints, DNA. The more of
these properties that we can identify, the better we know the person. In a
similar way matter has properties - and there are many of them. There are two
basic types of properties that we can associate with matter. These properties
are called Physical properties and Chemical properties. Physical properties are
Properties that do not change the chemical nature of matter. Chemical
properties are Properties that do change that chemical nature of matter. Examples
of physical properties are color, smell, freezing point, boiling point, melting
point, infra-red spectrum, attraction or repulsion to magnets, opacity,
viscosity and density. Examples of chemical properties are: heat of combustion,
reactivity with water, PH, and electromotive force. The more properties we can
identify for a substance, the better we know the nature of that substance.
A physical change in a substance doesn't change what the
substance is. In a chemical change where there is a chemical reaction, a new
substance is formed and energy is either given off or absorbed. For example, if
a piece of paper is cut up into small pieces it still is paper. This would be a
physical change in the shape and size of the paper. If the same piece of paper
is burned, it is broken up into different substances that are not paper. Physical
changes can be reversed, chemical changes cannot be reversed with the substance
changed back without extraordinary means, if at all. For example, a cup of
water can be frozen when cooled and then can be returned to a liquid form when
heated. When heat is given off in a chemical change or reaction, it is called
an exothermic reaction. When heat is absorbed in a chemical change or reaction,
it is called an endothermic reaction. The speed at which chemical reactions
take place depend on the temperature pressure and how concentrated the
substances involved in the chemical reaction are.
This picture shows examples of physical and chemical changes