2.1 The Water Cycle

the smallest particle of a substance that can take part in a chemical reaction

a group of atoms held together by sharing electrons between atoms in the molecule

a theory which describes the bulk properties of the different states of matter in terms of the movement of particles ( atoms or molecules )- the theory explains what happens during changes in physical state

the energy possessed by objects or particles due to movement

solid,liquid and gases are the three states of matter in which any substance can exist, depending on the conditions of temperature and pressure

the temperature at which a solid turns into a liquid; it has the same value as the freezing point

energy absorbed or released by a substance during a change in its physical state

the temperature at which a liquid boils

gaseous water in the air that has evaporated

the cycle of processes by which water circulates between the Earth’s oceans, atmosphere,and land , it involves precipitation,drainage and run off into streams and rivers,and return to the atmosphere by evaporation

layer of gases surrounding the surface of the earth

the change of a liquid into a solid; during this process heat is given out to the surroundings

the description of a substance that dissolves in a particular solvent

the random movement of particles from an area of higher concentration to an area of lower concentration ( down a concentration gradient); it is a passive process, not requiring the input of energy

the outer part or exposed area of a material

the proportion of water vapour in the air

water that falls from the atmosphere to the Earth’s surface as rain, sleet, snow or hail

water flowing over land to return to rivers and oceans ( can occur on natural surfaces such as rocks, soil and vegetation, or artificial surfaces such as roads and buildings)