1. Magnesium hydroxide reacts with nitric acid to produce magnesium nitrate and water.

Question

Mg(OH)2+2HNO3→Mg(NO3)2+2H2O
In one to two sentences, explain how because this chemical equation is balanced, it demonstrates that matter is neither created nor destroyed in a chemical reaction.

2. Methane (CH4) is a gas that is found in small quantities in Earth’s atmosphere. Are the bonds in methane ionic or covalent according to their electronegativities, and how can one carbon atom bond with four hydrogen atoms based on their valence electrons? In three to five sentences, explain your answer in 3 sentences

3. Processes are described as either endothermic or exotherm depending on whether energy is absorbed or lost. Cooking an egg is one type of process, while the formation of snow is another. In three to five sentences, determine which process is endothermic and which process is exothermic. Explain the reason for your answer in 3 sentences

Answer 1

1. The balanced chemical equation for the reaction between magnesium hydroxide and nitric acid shows that the number of atoms of each element is the same on both sides of the equation, demonstrating the conservation of mass. This indicates that during the chemical reaction, the total mass of the reactants equals the total mass of the products, thereby proving that matter is neither created nor destroyed.

2. The bonds in methane (CH₄) are covalent, as the electronegativity difference between carbon and hydrogen is small, allowing them to share electrons rather than transferring them. A carbon atom has four valence electrons and can form four covalent bonds by sharing one electron with each of the four hydrogen atoms, which each have one valence electron. This results in a stable arrangement where the carbon atom achieves a full outer shell by sharing electrons with the hydrogens.

3. Cooking an egg is an endothermic process because it requires the absorption of heat energy from the surroundings to denature the proteins in the egg. On the other hand, the formation of snow is exothermic since it releases heat into the environment as water vapor condenses and freezes. The distinction lies in the direction of energy flow: endothermic processes absorb energy, increasing internal energy and temperature, while exothermic processes release energy, resulting in a decrease in internal energy and temperature.