Chemistry

• In a combustion reaction, a substance reacts with oxygen to produce heat and light.
• The reactants undergo a chemical change to form new products.
• A balanced equation shows the relative number of atoms on both sides of the arrow.
• A chemical change is when the properties of a substance are changed irreversibly by breaking or forming bonds between atoms.
• A solution with a pH of 7 has an equal number of H+ and OH- ions, making it neutral.
• Matter can transform from one unit state to another due to changes in temperature or pressure.
• The properties of a substance depend on its unit state.
• The pH scale is logarithmic, with each whole number representing a tenfold change in hydrogen ion concentration.
• Examples of physical changes include melting, boiling, freezing, evaporating, dissolving, filtering, crystallizing, and separating mixtures using filtration, distillation, and chromatography.