Year 10 Chemistry Revision Complete Solutions
Elements, Molecules, and Compounds
In its purest form, an element consists of atoms with the same composition. A molecule is formed when
two or more atoms, identical or different, bond together. A compound, on the other hand, is created
when two...
In its purest form, an element consists of atoms with the same composition. A molecule is formed when
two or more atoms, identical or different, bond together. A compound, on the other hand, is created
when two or more different atoms combine in a fixed ratio.
Atoms and Ions
The smallest particle of matter with a consistent composition is an atom. An ion is formed when an
atom loses or gains an electron, resulting in an overall charge. Isotopes are variations of elements that
have the same number of protons but differ in the number of neutrons.
Physical and Chemical Changes
, Physical changes are reversible transformations that involve a change in state. For example, solid-to-
liquid (ice to water) or solid-to-gas (dry ice to CO2 gas) transformations do not alter the molecular
structure. In contrast, chemical changes are irreversible processes that involve the formation of new
compounds with distinct properties and appearances. These changes are often marked by color
changes, fizzing or gas release, or odor emission.
Key Takeaways
* Elements are substances with identical atoms.
* Molecules are formed by combining identical or different atoms.
* Compounds result from combining different atoms in a fixed ratio.
* Atoms can become ions by gaining or losing electrons.
* Isotopes differ in neutron count despite having the same number of protons.
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