- How do sub-atomic particles help us to understand the structure of substances?
Simple particle theory is developed in this unit to include atomic structure and bonding. The arrangement of electrons in atoms can be used to explain what happens when elements react and how atoms join together to form different types of substances.
- How do structures influence the properties and uses of substances?
Substances that have simple molecular, giant ionic and giant covalent structures have very different properties. Ionic, covalent and metallic bonds are strong. The forces between molecules are weaker, eg in carbon dioxide and iodine. Nanomaterials have new properties because of their very small size.
- How much can we make and how much do we need to use?
The relative masses of atoms can be used to calculate how much to react and how much we can produce, because no atoms are gained or lost in chemical reactions. In industrial processes, atom economy is important for sustainable development.
How can we control the rates of chemical reactions?
Being able to speed up or slow down chemical reactions is important in everyday life and in industry. Changes in temperature, concentration of solutions, surface area of solids and the presence of catalysts all affect the rates of reactions.
Do chemical reactions always release energy?
Chemical reactions involve energy transfers. Many chemical reactions involve the release of energy. For other chemical reactions to occur, energy must be supplied. In industrial processes, energy requirements and emissions need to be considered both for economic reasons and for sustainable development.
How can we use ions in solutions?
Ionic compounds have many uses and can provide other substances. Electrolysis is used to produce alkalis and elements such as chlorine and hydrogen. Oxidation-reduction reactions do not just involve oxygen. Soluble salts can be made from acids and insoluble salts can be made from solutions of ions.