2024 Exam! AQA Foundation Chemistry Paper 1

Recent questions

• What is a covalent bond?

  A covalent bond is a type of chemical bond formed when two non-metal atoms share pairs of electrons. This sharing allows each atom to attain a stable electron configuration, similar to that of noble gases. Covalent bonds can vary in strength, with single bonds involving one shared pair of electrons, double bonds involving two pairs, and triple bonds involving three pairs. The resulting molecules can exhibit different properties based on the number of shared electrons and the types of atoms involved. For example, in a molecule of oxygen (O2), each oxygen atom shares two pairs of electrons, resulting in a strong double bond. Covalent bonding is fundamental in the formation of many organic compounds and is characterized by strong intramolecular forces, although the intermolecular forces between covalent molecules are generally weaker.

• How do you calculate relative atomic mass?

  Relative atomic mass is calculated by taking into account the different isotopes of an element and their respective abundances. To find the relative atomic mass, you multiply the mass of each isotope by its natural abundance (expressed as a fraction), then sum these values. For instance, chlorine has two stable isotopes: chlorine-35, which makes up about 75% of natural chlorine, and chlorine-37, which accounts for about 25%. The calculation would be: (0.75 x 35) + (0.25 x 37) = 26.25 + 9.25 = 35.5. This average gives the relative atomic mass of chlorine as 35.5. This concept is crucial in chemistry as it helps in understanding the mass relationships in chemical reactions and the behavior of elements in the periodic table.

• What is the conservation of mass?

  The conservation of mass is a fundamental principle in chemistry stating that the total mass of reactants in a chemical reaction must equal the total mass of products. This means that matter cannot be created or destroyed in an isolated system. For example, if 73 grams of hydrochloric acid react with 100 grams of calcium carbonate, the total mass of the reactants is 173 grams. If the reaction produces water and other products, the combined mass of these products must also equal 173 grams. This principle is essential for balancing chemical equations, as it ensures that the number of atoms of each element remains constant throughout the reaction. Understanding the conservation of mass is crucial for accurately predicting the outcomes of chemical reactions and for conducting quantitative analyses in chemistry.

• What are giant covalent structures?

  Giant covalent structures are large networks of atoms bonded together by strong covalent bonds, resulting in materials with high melting and boiling points. These structures do not consist of individual molecules but rather a continuous lattice of atoms. Examples include diamond, graphite, and silicon dioxide. In diamond, each carbon atom is tetrahedrally bonded to four other carbon atoms, creating a very hard material. Graphite, on the other hand, consists of layers of carbon atoms arranged in hexagonal patterns, with weak forces between the layers allowing them to slide over one another, making graphite useful as a lubricant. Silicon dioxide, commonly found in sand, forms a three-dimensional network that gives it high stability and strength. The properties of giant covalent structures make them significant in various applications, from industrial materials to electronics.

• What is an endothermic reaction?

  An endothermic reaction is a type of chemical reaction that absorbs heat from its surroundings, resulting in a decrease in temperature of the environment. During an endothermic reaction, the energy required to break the bonds of the reactants is greater than the energy released when new bonds are formed in the products. A common example of an endothermic reaction is the process of photosynthesis, where plants absorb sunlight to convert carbon dioxide and water into glucose and oxygen. In a laboratory setting, endothermic reactions can be observed using a thermometer; as the reaction occurs, the thermometer reading will drop, indicating that heat is being absorbed. Understanding endothermic reactions is important in various fields, including chemistry, biology, and environmental science, as they play a crucial role in energy transfer and transformation processes.