TEMA 6 SCIENCE

UNIT 6

SURFACE WATER

RIVER

-          A river is a flow of water that is bigger and deeper than a stream.

STREAM

-          A stream is a very small river that originates in mountains.

LAKE

-         A lake is a large area of water surrounded by land.

-         Most lakes on the Earth contain fresh water.

GLACIER

-          A glacier is an area of moving ice.

-          Glaciers form in high altitudes.

OCEAN

-          An ocean is a huge area of salt water.

-          There is only one ocean, called the World Ocean.

-          The World Ocean consists of five interconnected parts:

·         The Pacific ocean.

·         The Atlantic ocean.

·         The Indian ocean.

·         The Artic ocean.

·         The Southern ocean.

GROUNDWATER

-          Groundwater is water found below the surface of the Earth.

-          Most groundwater comes from rainfall.

-         A spring is the place where the ground water meets the Earth´s surface.

-         We find groundwater in layers of sandstone called aquifers.

-         Below an aquifer there is a layer of clay that traps the water.

-         To get groundwater out of aquifers we use pipes and wells.

THE THREE STATES OF WATER

We can find water in nature in three different states:

LIQUID  WATER

-         Rain, water in rivers, lakes and oceans are examples of water in a liquid state.

GASEOUS  WATER

-         Clouds, steam, fog and mist are examples of water in a gaseous state.

-         It is quite difficult to see water in this state.

SOLID WATER

-         Ice, snow and hail are examples of water in a solid state.

CHANGES IN THE STATES OF WATER

CONDENSATION: GAS TO LIQUID

-         Condensation is the change from the gaseous state to the liquid state.

EVAPORATION:  LIQUID TO GAS

-         Evaporation is the change from the liquid state to the gaseous state.

FREEZING:  LIQUID TO SOLID

-         Freezing is the change from the liquid state to the solid state.

MELTING: SOLID TO LIQUID

-         Melting is the change from the solid state to the liquid state.

SUBLIMATION: SOLID TO GAS

-         Sublimation is the change from the solid state to the gaseous state.

DEPOSITION: GAS TO SOLID

-         Deposition is the change from the gaseous state to the solid state.

THE WATER CYCLE

EVAPORATION

-         The Sun heats water in rivers, lakes and oceans and turns it into vapour.

CONDENSATION

-          Vapour from the air cools and turns into clouds.

PRECIPITATION

-          When a big amount of water condenses, it falls as precipitation: rain, snow or hail.

COLLECTION

-         When water falls, it forms rivers, lakes, oceans…

USES OF WATER

RECREATIONAL  USE

-         We use water for a lot of recreational activities, for example: fishing, swimming, sailing…

HYDROPOWER

-          Water is a renewable source of energy

-          We use the hydropower to produce electricity.

AGRICULTURAL  USE

-          We use approximately  70%  of the water in the world for irrigation.

AT  HOME

-          We use water for drinking, showering, cooking and washing.

-          A person in Spain uses approximately  50 litres of water per day.