Matter and Chemical Change

Distinguish chemical from physical changes and learn the basics of reactions.

11 questions, free, marked as you go with a worked explanation on every one.

What this covers

The questions

  1. A change that produces a new substance is called a:
  2. Which of these is a sign of a chemical change?
  3. The smallest unit of an element that retains its properties is a(n):
  4. Two or more elements chemically combined form a:
  5. In a chemical reaction, the substances you start with are called:
  6. In a sealed flask, 12.0 g of magnesium is burned with 7.9 g of oxygen, and the two react completely to form magnesium oxide. The flask stays sealed the whole time, so nothing can enter or escape. What mass of magnesium oxide is produced, in grams?
  7. A student times how long an antacid tablet takes to react completely in a beaker of water. A whole tablet takes 90 seconds. An identical tablet, crushed to powder first, takes 30 seconds. How many times faster is the reaction with the crushed tablet?
  8. On the periodic table, aluminium has an atomic number of 13. How many protons and electrons are in one neutral aluminium atom?
  9. A reaction happens faster at a higher temperature. Which particle-level explanation fits this?
  10. The particle model describes matter as being made of tiny moving particles. What are those particles called in the atomic theory you are learning in this unit?
  11. Dry ice (solid carbon dioxide) and the gas it turns into when it sublimes are both made of the same CO2 particles. Which statement best explains why one is a solid and the other a gas at the same pressure?

Answer these free