Matter can exist in one of three main states: solid, liquid, or gas.
Solid matter is composed of tightly packed particles. A solid will retain its shape; the particles are not free to move around.
Liquid matter is made of more loosely packed particles. It will take the shape of its container. Particles can move about within a liquid, but they are packed densely enough that volume is maintained.
Gaseous matter is composed of particles packed so loosely that it has neither a defined shape nor a defined volume. A gas can be compressed
liquid: A substance that flows and keeps no definite shape because its molecules are loosely packed and constantly moving. It takes the shape of its container but maintains constant volume.
gas: A substance that can only be contained if it is fully surrounded by a container (or held together by gravitational pull); a substance whose molecules have negligible intermolecular interactions and can move freely.
solid: A substance that retains its size and shape without a container; a substance whose molecules cannot move freely except to vibrate.
I believe the answer is 1960's
