How do chemical processes occur? Which kinds of changes are observed in them?

(N/A) $\rightarrow$ Chemical compounds undergo two types of changes:
$(1)$ Physical change: Change in shape or state of matter without breaking of chemical bonds. For example,ice melting into water or water becoming vapour.
$(2)$ Chemical change: When bonds are broken and new bonds are formed during transformation,it is called a chemical reaction. For example,$Ba(OH)_{2} + H_{2}SO_{4} \rightarrow BaSO_{4} + 2H_{2}O$ (inorganic) or hydrolysis of starch into glucose (organic).
$\rightarrow$ Rate of a process refers to the amount of product formed per unit time. $\text{Rate} = \frac{\delta p}{\delta t}$.
$\rightarrow$ Rates are influenced by temperature; a rule of thumb is that the rate doubles or decreases by half for every $10^{\circ}C$ change.
$\rightarrow$ Catalysed reactions proceed much faster. For example,the enzyme carbonic anhydrase increases the rate of $CO_{2} + H_{2}O \rightarrow H_{2}CO_{3}$ by about $10$ million times.
$\rightarrow$ $A$ metabolic pathway is a multistep chemical reaction where each step is catalysed by specific enzymes. For example,the conversion of glucose to pyruvic acid involves $10$ different enzyme-catalysed reactions.