Water Water water everywhere

The structure of Water 1. It can be quite correctly argued that life only exists on Earth because of the abundance of liquid water. 2. Other planets have water, but they either have it as a gas (Venus) or ice (Mars). 1. Water can exist in all three states of matter on Earth, while only in one state on our two nearest neighboring planet 3. Water is liquid between 0 o C and 100 o C which is critical for life

Properties of Water! H 2 O! 1. Water resists temperature changes. 1. This property moderates earth's surface temperature; 2. Allows living systems to exist here on earth 3. When animals sweat, evaporation of the sweat takes away body heat, thus cooling the animal.

Properties of Water! Water! 2. Water is polar, 1. Electrons spend more time near the Oxygen atom in water molecules. 2. This creates a partial negative charge near the O 3. This makes water a polar molecule

Properties of Water! Water! 3. Water expands when it freezes 1. Ice is less dense than liquid water 2. Remember that Density= Mass/Volume 3. Ice has less mass per volume of liquid water

Properties of Water! Water! 4. Water molecules are cohesive and adhesive. 1. Cohesion allows water to flow freely without molecules separating 2. Surface of water has structure, think of skipping a rock, or insects that walk on water 3. Water sticks to itself, this allows water to be moved from the roots to leaves in plants

Water and Covalent Bonds 1. Water is polar covalently bonded within the molecule. 1. polar covalent bond: covalent bond in which atoms share electrons in an unequal fashion. covalent bond in which atoms share electrons in an unequal fashion. 2. Water shares electrons unevenly creating a polar molecule Water shares electrons unevenly creating a polar molecule

Hydrogen Bonds 1. Hydrogen bond : A weak bond between two atoms (one of which is hydrogen) with partial but opposite electrical charges. 2. Hydrogen must be involved for it to be a hydrogen bond!!!

Hydrogen Bonds 3. This partial charge allows water molecules to bond easily with each other. 1. In the image to the right, there are 4 water molecules bonded together by hydrogen bonds. 4. They are the weakest of the 3 bonds. 5. Hydrogen Bonds can break and form very easily.

Diffusion 1. All objects in motion have kinetic energy. 2. Particles move in a straight line until they hit another particle. 3. Particles of matter, like water molecules are also in this constant state of motion

Brownian Motion 1. In 1827 Robert Brown observed non-living particles moving in erratic motion under a microscope 2. He was observing the random motion of particles, now called Brownian Motion 3. This random motion is found in all gas, liquids, and some solid molecules

Process of Diffusion  Different substances that are in constant motion have an effect on each other  Two liquids put together will eventually mix  Diffusion: the net movement of particles from an area of high concentration to an area of low concentration Low concentration of copper sulphate High concentration of copper sulphate

Effects on Diffusion  Diffusion is a slow process  It can be sped up by two external factors 1. by increasing temperatures 2. And increasing pressure  Sugar dissolves in hot tea faster than cold tea!