Chemistry Revision

• What are the three states of matter?

  Solid, liquid, and gas.
• How do particles behave in solids?


  In solids, particles are tightly packed and vibrate.
• How do particles behave in liquids?


  In liquids, particles move freely but stay close.
• How do particles behave in gases?


  In gases, particles move quickly and are far apart.
• What happens to particles when a substance is heated?


  Particles gain energy, move faster, and may change state.
• How do changes in temperature affect the state of matter?


  Increasing temperature can cause melting or boiling, while decreasing temperature can cause freezing or condensation.
• What is the difference between boiling and evaporation?


  Boiling occurs throughout a liquid at a specific temperature, while evaporation happens only at the surface, at any temperature.
• What is an atom?


  The smallest unit of an element that retains its chemical properties.
• What is the difference between an element and a compound?


  An element contains only one type of atom, while a compound consists of two or more different atoms chemically bonded.
• What are the three subatomic particles in an atom?


  Protons, neutrons, and electrons.
• How are elements represented on the periodic table?


  Each element is represented by a symbol (e.g., O for oxygen, H for hydrogen).
• What is a molecule?


  A molecule is two or more atoms bonded together, either of the same or different elements.
• What is a mixture?


  A combination of two or more substances that are not chemically bonded.
• How can mixtures be separated?


  Mixtures can be separated by physical methods like filtration, distillation, or chromatography.
• What is the difference between a homogeneous and heterogeneous mixture?


  Homogeneous mixtures are uniform throughout, while heterogeneous mixtures have distinct parts.
• How does filtration work to separate mixtures?


  Filtration separates solids from liquids by passing the mixture through a filter.
• What is a solution?


  A solution is a mixture where a solute is completely dissolved in a solvent (e.g., saltwater).
• What is an acid?


  A substance with a pH less than 7 that donates hydrogen ions (H⁺) in solution.
• What is an alkali?


  A substance with a pH greater than 7 that releases hydroxide ions (OH⁻) in solution.
• What is the pH scale used for?


  The pH scale measures how acidic or alkaline a substance is, ranging from 0 (very acidic) to 14 (very alkaline).
• What happens in a neutralization reaction?


  An acid reacts with an alkali to produce water and a salt.
• What is an indicator?


  A substance that changes color depending on whether it is in an acidic or alkaline solution (e.g., litmus paper).
• What is a chemical reaction?


  A process where substances (reactants) change into new substances (products) with different properties.
• What is the law of conservation of mass?


  Mass is conserved in a chemical reaction; the total mass of reactants equals the total mass of products.
• What are physical changes?


  Physical changes involve changes in state or appearance without forming new substances (e.g., melting, freezing).
• What is the difference between endothermic and exothermic reactions?


  Endothermic reactions absorb energy (heat), while exothermic reactions release energy.
• What is a catalyst?


  A substance that speeds up a chemical reaction without being consumed in the process.
• What are natural resources?


  Materials found in nature, such as water, minerals, and fossil fuels, used by humans.
• What is sustainable use of resources?


  Using resources in a way that meets current needs without depleting them for future generations.
• What is recycling?


  The process of converting waste materials into new, usable products.
• How are metals extracted from ores?


  Metals are extracted from ores through methods like heating (smelting) or electrolysis.
• What is renewable energy?


  Energy from sources that can be replenished, such as solar, wind, and hydroelectric power.
• What is combustion?


  A chemical reaction between a fuel and oxygen that releases energy in the form of heat and light.
• What are the products of complete combustion?


  Carbon dioxide and water.
• What is incomplete combustion?


  Combustion that occurs with insufficient oxygen, producing carbon monoxide and soot.
• Why is carbon monoxide dangerous?


  Carbon monoxide is a toxic gas that can prevent the blood from carrying oxygen around the body.
• What is a fuel?


  A material that releases energy when burned, such as coal, oil, or natural gas.