According to the chemistry study note of Kevy, when atoms rearrange to generate new compounds, a chemical reaction takes place involving one or more of the original substances. The collision theory, which states that particles (atoms or molecules) must collide with sufficient energy and in the right orientation for a reaction to occur, is frequently used to explain this change. Even though there are many collisions, not all of them cause a response.
Kevy also notes that the release of gas (effervescence), the creation of a precipitate, color changes, light production, and heat or flame emission are all signs of a chemical reaction. Chemical equations are symbolic depictions of these reactions that use formulas to describe the products (the newly formed compounds displayed on the right of the arrow) and reactants (the starting substances on the left of the reaction arrow).
In addition, according to Kevy , the equation may contain symbols for other physical states, such as solid, liquid, gas, or aqueous solutions. It may also indicate modifications, such as the addition of heat or the presence of a catalyst, like platinum, to speed up the reaction.
According to Maria’s study notes on chapter 8.2 of the chemistry class, there are different types of chemical reactions.
First, we examine synthesis or combination reactions, where two or more reactants combine to form a single product, exemplified by reactions like H2 + O2 → H2O and Mg + O2 → MgO. There are no special conditions required for these reactions.
Next, decomposition reactions are explored, where a single compound breaks down into two or more products, such as H2O2 → H2O + O2 and MgCO3 → MgO + CO2.
The third type covered is single displacement or replacement reactions, where an element reacts with an ionic compound, leading to reactions like Li + Fe2O3 → Li2O + Fe and F2 + HBr —> HF + Br2, with the condition that the element must be more reactive according to the activity series of metals or the periodic table for halogens.
Lastly, double displacement reactions involve the exchange between two ionic reactants to form products such as AgNO3(aq) + BaCl2(aq) → AgCl(s) + Ba(NO3)2(aq), where one of the products is typically a solid, liquid, or gas.
