During exothermic reactions:
a. heat is transformed into potential energy
b. kinetic energy is transformed into bond energy
c. potential energy is transformed into bond energy
d. potential energy is transformed into kinetic energy
c. potential energy is transformed into bond energy
During exothermic reactions, the correct option is:
c. potential energy is transformed into bond energy
Exothermic reactions are those in which the overall energy of the system decreases, and energy is released to the surroundings in the form of heat. In these reactions, the reactants have a higher potential energy compared to the products. As the reaction proceeds, the potential energy stored in the chemical bonds of the reactants is transformed into the bond energy of the products, resulting in the release of heat energy. Therefore, option c is the correct answer.
During exothermic reactions, the correct answer is: d. potential energy is transformed into kinetic energy.
To understand why, let's first clarify what an exothermic reaction is. An exothermic reaction is a chemical reaction that releases energy in the form of heat to the surrounding environment. This means that the system loses energy, and the energy is transferred from the system to the surroundings.
In exothermic reactions, the reactants have a higher potential energy than the products. Potential energy is the energy stored within a system due to its position or arrangement. As the reactants undergo a chemical reaction, the arrangement of atoms changes, and chemical bonds are made or broken. This process lowers the potential energy of the system.
When the potential energy decreases, the excess energy is released as heat and transferred to the surroundings. As a result, the potential energy is transformed into kinetic energy, which is energy associated with the movement of particles. This increase in kinetic energy is observed as an increase in temperature.
It's important to note that while heat is released during exothermic reactions, it is not transformed into potential energy, as stated in option a. Potential energy is related to the arrangement and position of particles, whereas heat energy is associated with the movement and thermal energy of particles.
Similarly, option c, which states that potential energy is transformed into bond energy, is not accurate. Bond energy is the energy required to break or form a chemical bond, and it is not directly related to potential energy.
Option b, stating that kinetic energy is transformed into bond energy, is also incorrect. Kinetic energy is the energy associated with moving particles, whereas bond energy is related to the strength of chemical bonds.
In summary, during exothermic reactions, the potential energy of the system decreases, and the excess energy is released as heat, leading to an increase in the kinetic energy of the surroundings. Therefore, the correct answer is option d, potential energy is transformed into kinetic energy.
2. Which of the following are chemical changes?
a. mercury has a density of 13600 kg/m3
b. potassium reacts with water
c. hammer a nail into a piece of wood
d. a rotting apple
e. potassium is a soft metal
f. evaporation of water g. sublimation of dry ice
h. dissolve sugar in water
i. a growing flower
j. hydrogen is a flammable gas
The chemical changes among the given options are:
b. potassium reacts with water - This is a chemical change because a chemical reaction occurs between potassium and water, resulting in the formation of potassium hydroxide and hydrogen gas.
d. a rotting apple - This is a chemical change because the organic matter in the apple undergoes decomposition, resulting in the formation of new substances through chemical reactions.
f. evaporation of water - This is a physical change, not a chemical change. Evaporation is the process by which water changes from a liquid to a gas state without undergoing a chemical reaction.
g. sublimation of dry ice - This is a physical change, not a chemical change. Sublimation is the process by which a substance directly changes from a solid to a gas state without going through the liquid phase.
h. dissolve sugar in water - This is a physical change, not a chemical change. Dissolution is a physical process where a solute (sugar) disperses in a solvent (water) without any chemical reaction occurring.
i. a growing flower - This is a biological process involving the growth and development of plant cells, which includes chemical changes occurring within the plant. However, strictly speaking, the growth and development of a flower is a biological process and not solely a chemical change.
j. hydrogen is a flammable gas - The statement is true, but it describes a physical property of hydrogen rather than a chemical change. Flammability is a property of a substance, and it does not necessarily involve a chemical reaction.
Therefore, the correct chemical changes among the options are b. potassium reacts with water and d. a rotting apple.