Overview What is life What is a habitable zone? Phases of matter What is water? What is so special about water Hydrological cycle
Definition of life “Life is a self-sustained chemical system capable of undergoing Darwinian evolution” Cleland in “Defining Life”, Evolution of life and the evolution of the biosphere, 93, 2002.
What is Life? The condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional... Living things and their activity: "some sort of life existed on Mars".
Water is all around us. It is in our bodies. It is in our homes. We have rivers, lakes and oceans. We have wet weather.
Water is a liquid but it can change into other things. Water changes as it is warmed up and changes again when it cools down. It can freeze and become ice. It can heat up and become steam.
Global Allocation of water 70% of the earth is covered with water 97% of the water is in the ocean 2.2 % is covered in ice 0.7% is underground 0.3% is surface water 0.03% is at the atmosphere 0.02% is in the biosphere
H H O STRUCTURE OF WATER The bond that forms water is a covalent bond
Stages of matter SOLID LIQUID GAS
Properties of Water Cohesion Adhesion High Specific Heat High Heat of Vaporization Less Dense as a Solid
Surface Tension
Water is Less Dense as a Solid Which is ice and which is water? Which is ice and which is water?
A Habitable Zone? Not too hot (< ºC) Not too cold (>0 ºC) Not too acid / alkaline (pH 6-8) Not too salty Not too little or too much radiation Dole 1960:
HABITABLE ZONES The range of distances around a central star at which Earth-like planets maintain conditions sufficient for the existence of life at the surface. First publications: Huang (1959, 1960), Dole (1964), Shklovski & Sagan (1966)
The sun is warming the surface of the water. As the water gets warmer it changes and begins to evaporate. The warm water changes into a gas called water vapour and rises up. Water is a liquid. The water vapour cools down and forms clouds. This is condensation. When a cloud gets full it begins to rain. This is called precipitation. This is called The Water Cycle
Water never leaves the Earth. It is constantly being cycled through the atmosphere, ocean, and land. This process, known as the water cycle, is driven by energy from the sun. The water cycle is crucial to the existence of life on our planet.
Evaporation Condensation Precipitation
Evaluation Questions Why water floats when it is in a solid state? Write all stages of water cycle in order Why the world has a scarcity of water? What can be done to curb this problem.
His wisdom is seen in his creation