Ace the Cambridge Science Challenge 2026 – Master the Mysteries of Matter!

Think of a space with no matter at all. That is called a vacuum. A vacuum means extremely low density of particles and very low pressure, essentially an area devoid of matter compared with everyday surroundings. The other terms describe either a movement (flow) or a change or state of matter (boil and steam). So vacuum is the correct term because it directly names a space lacking matter.