Physical VS Chemical Change Flashcards
Characteristics of physical changes
No new substance is formed.
No change in the chemical properties of the substance.
Physical change usually involves a change in energy, energy is usually either taken in or given out during a physical change.
Electrical conductivity (resistance) may change - either a greater current is allowed to pass through a material or it decreases when it is heated.
Material may expand on heating and contract on cooling.
Substance melts/boils on heating and freeze/condense on cooling.
Color change
The change is often reversible.
Physical changes affect physical properties of matter
Color
Sixe
Shape
Density
Mass
Electric conductivity
Phase of substances
A catalyst
Speeds up the rate of a chemical reaction
Definition of the physical change
A physical change affects the form or appearance of a substance but does not change its chemical composition.
Examples of physical changes
Melting ice (solid to liquid).
Tearing paper.
Dissolving sugar in water.
Chemical change definition
Definition: A chemical change results in the formation of one or more new substances, with different chemical properties from the original substances.
Characteristics of chemical change
Characteristics:
New substances are produced.
The change is usually not reversible by simple physical means.
Often accompanied by energy changes (heat, light, etc.).
It’s color may change
Chemical change always result in
The rearrangement of the atoms of combining substances (the reactants) to form the product ls of the reaction
Examples of chemical changes
Burning wood (wood turns into ash, carbon dioxide, and water vapor).
Rusting of iron (iron reacts with oxygen to form iron oxide).
Digesting food (chemical breakdown of food into new substances).
Differences between chemical and physical changes
Physical changes do not alter the chemical composition of a substance, while chemical changes result in new substances with different properties.
Physical changes are typically reversible, while chemical changes are often irreversible under normal conditions
Synthesis reactions
The product is formed is a more complex substance than each of its reactants.
Those in which two or more substances combine chemically to form more complex compounds
Decomposition
A compound breaks down to form simpler substances.
In an isolated system energy cannot be created or destroyed, it can only be transferred from one place to another
All matter has a certain amount of internal energy due to the motion of its particles and it has chemical potential energy stored in the bonds that holds atoms together. These bonds must break in order for a chemical reaction to take place. All chemical reactions take in energy to break the bonds.
When new bonds form energy is released in the form of heat and light
The total energy transferred during the reaction is equal to to the difference between the amount of energy taken in and the amount of energy released
Exothermic reactions
Reactions that release more energy than they take in. Thermal energy leaves the reaction vessel to warm up the surrounding air. Like hydrogen and oxygen, energy is released as heat, light and sound in this explosion
