1. the starting materials completely lose their
properties to form new substances chemical change
2. a change from one state of matter to another phase change
3. a change in shape, size, or physical
characteristics but remaining same substance physical change
4. a pure compound consists of exactly
the same elements in the exact same
ratios by mass Law of Constant Composition
5. The smallest unit of a compound molecule
Explanation:
A chemical change is a kind of change in which new kind of matter is formed. It is always with energy changes in moving from reactants to products. Chemical changes are not easily reversible. Examples are combustion, rusting of iron, precipitation etc.
A phase change is simply the transition from one state of matter to another. It can be from solid to liquid, liquid to gas, gas to solid, gas to liquid. Some of the phase change processes are condensation, evaporation, sublimation, melting and freezing.
Physical change is a change that alters the physical properties of matter particularly their form and state. Most physical changes are easily reversible. Examples are; boiling, melting, condensation, freezing etc.
Law of constant composition states all pure samples of the same chemical compounds contain the same proportion of the elements by mass. It is also known as the law of definite proportion.
A molecule is the smallest unit of a compound. It can be derived from the combination of atoms or a single atom. It is on this that compounds are built.
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