Final answer:
The question deals with identifying chemical and physical changes through examples provided in chemical equations. Physical changes involve changes in physical state without altering chemical identity, whereas chemical changes result in new substances with new properties. Balancing chemical equations requires an equal number of each type of atom on both sides.
Step-by-step explanation:
The question asks about the classification of chemical and physical changes using different chemical equations as examples. A chemical change involves the transformation of substances into new substances with different chemical properties, while a physical change involves a change in physical properties without altering the chemical identity.
Physical change: H2O(s) → H2O(l) represents the melting of ice into water, which is a change of state—a typical physical change since the chemical composition (H2O) remains the same.
Chemical change: CH3OH(g) + O2(g) → CO2(g) + H2O(g) represents a combustion reaction, which is a chemical change because new substances (CO2 and H2O) are formed, and the original molecule (CH3OH) is transformed.
A net ionic equation represents only the species that change throughout the reaction. The equation H+ (aq) + OH- (aq) → H2O(l) is a net ionic equation for the neutralization reaction between acids and bases.
To determine if an equation is balanced, one must ensure that there are equal numbers of each type of atom on both sides of the equation. For instance:
2Na(s) + O2(g) → 2Na2O(s) is not balanced because the sodium (Na) atoms differ on both sides.
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) is balanced as there are equal numbers of carbon (C), hydrogen (H), and oxygen (O) atoms on both sides of the equation.
AgNO3(aq) + KCl(aq) → AgCl(s) + KNO3(aq) is balanced as-is, with each element having the same number of atoms on both sides.