Chemistry Focus Questions

• To find the two substances in a mystery mixture:

  • Add water and let it evaporate
  • Test multiple combinations
  • Observe residue and color
  • Feel temperature change
  • Observe similarities & differences
• The periodic table of elements is a table containing all known elements and possible elements based on chemical properties
• All substances on Earth are made up of elements
• To study a gas produced in a chemical reaction, you can capture the gas using a balloon or a syringe
• Air is matter, as matter has mass and takes up space, and air has mass and takes up space
• Particles make up all matter, and there is nothing between gas particles except empty space
• When air is heated, particles move farther away and expansion occurs with more kinetic energy; when air cools, particles move closer and contraction occurs with less kinetic energy
• Not all substances form solutions in water; two non-water substances can combine to form a solution without needing water
• In dissolving, solute particles slide in between solvent particles until there is no room left, and solvent particles collide with solute particles, spreading uniformly
• Saturation in dissolving means if the solvent is fully saturated, there is no room left between the particles for more solute to dissolve
• The concentration of solutions is affected by the amounts of substances; the more of the substance there is, the higher the concentration, e.g., the ratio 5:10 is less concentrated than 10:10
• Atoms combine by creating bonds to hold themselves together and form new substances
• During a chemical reaction, particles break bonds and rearrange to form new substances
• When hydrochloric acid reacts with sodium bicarbonate, a chemical reaction occurs
• In a sample of liquid, when heated, particles move more and the liquid expands, while when cooled, particles move less and the liquid contracts
• In a sample of solid, when heated, particles vibrate more and loosen, while when cooled, particles vibrate less and tighten
• When two equal volumes of hot and cold water are mixed, the final temperature is the average between the two temperatures
• Energy transfers from hot to cold substances through conduction,, and through particles' contact/collision
• Heat is measured in calories
• A solid changes into a liquid through melting when heated
• Heat of Fusion is the energy needed to melt a substance, affecting the energy transfer between substances
• Melting is a phase change, while dissolving is a chemical change where the solute becomes part of the solvent, creating a new substance