GCSE Chemistry Quiz

Explanation
Exothermic reactions release heat energy. This means that the products of the reaction have less energy than the reactants, resulting in a release of energy in the form of heat. Therefore, the statement that chemical reactions where heat energy is given out are described as exothermic is true.

Explanation
Sodium is actually a highly reactive element. It is a member of the alkali metal group, which is known for its high reactivity. Sodium readily reacts with water, oxygen, and many other substances. It is stored in oil to prevent its reaction with air. Therefore, the statement that sodium is the least reactive element is false.

Explanation
The statement is incorrect because exothermic reactions are represented by a negative value of ΔH, indicating that heat is released during the reaction. The symbol ΔH represents the change in enthalpy, which is a measure of heat energy. Therefore, the correct statement would be that an exothermic reaction can be shown as -ΔH.

Explanation
Chemical reactions that absorb or take in heat energy are known as endothermic reactions. In these reactions, the reactants absorb heat from their surroundings, resulting in a decrease in the temperature of the surroundings. This is why endothermic reactions often feel cold to the touch. The statement "True" confirms that the given explanation is correct.

Explanation
The symbol for hydrogen is H, not K. Therefore, the statement "K is the symbol of hydrogen" is false.

Explanation
The symbol for water is H2O because it consists of two hydrogen atoms and one oxygen atom. This combination of atoms creates the chemical formula for water, which is H2O. Therefore, the statement "H2O is the symbol of water" is true.

Explanation
The statement is not accurate. For an element to react, it does not necessarily need to have more than 8 electrons. The reactivity of an element depends on its electron configuration and the number of valence electrons it has. Some elements with fewer than 8 electrons in their outermost energy level can still be reactive, such as the alkali metals which have only 1 valence electron. Therefore, the statement is false.

Explanation
In an exothermic reaction, heat energy is released to the surroundings, resulting in a decrease in the system's internal energy. This release of energy is often observed as an increase in temperature or the production of light. Therefore, it is correct to say that energy is lost in an exothermic reaction.

Explanation
Endothermic reactions are chemical reactions that absorb heat from their surroundings. The symbol ΔH represents the change in enthalpy, which is the heat absorbed or released during a reaction. When a reaction is endothermic, it means that the enthalpy change is positive, indicating that heat is being absorbed. Therefore, the statement "+ΔH" accurately represents endothermic reactions, making the answer "True".

Explanation
The statement is false because the making of bonds is not known as morphism. Morphism refers to a concept in mathematics and category theory that describes the relationship between two mathematical objects. Bonds, on the other hand, are typically associated with chemistry and refer to the connection between atoms in a molecule. While there may be some similarities in the sense that both involve a connection or relationship, they are not synonymous terms.