Properties of Water

 Why does ice float? A.Because it evaporates at 100°C B.Because it forms pockets of empty space when frozen C.Because it is a universal solvent D.Because it melts at 0°C  Why does ice float? A.Because it evaporates at 100°C B.Because it forms pockets of empty space when frozen C.Because it is a universal solvent D.Because it melts at 0°C

 Which best describes the movement of water molecules in a glass of liquid water? A.The molecules all move at the same speed B.The molecules all move at different speeds C.The molecules are not moving D.The molecules only move when you move the glass of water.  Which best describes the movement of water molecules in a glass of liquid water? A.The molecules all move at the same speed B.The molecules all move at different speeds C.The molecules are not moving D.The molecules only move when you move the glass of water.

Think pair share  Do you know what the term polar means?  How do you think polar relates to molecules?  Do you know what the term polar means?  How do you think polar relates to molecules?

What is water?  Think-Pair-Share with your table mates to answer the questions below  What is the chemical formula for water?  What does the formula tell us about water?  What kind of chemical bond do you think water has?  Think-Pair-Share with your table mates to answer the questions below  What is the chemical formula for water?  What does the formula tell us about water?  What kind of chemical bond do you think water has?

What water is made of… H 2 O Stop at 3 min 50 sec.

Video notes  Electrolysis breaks water apart into  2 parts hydrogen and 1 part oxygen  Electrolysis breaks water apart into  2 parts hydrogen and 1 part oxygen

Water’s covalent bonds  Sometimes in covalent bonds there is an unequal sharing of electrons in a molecule.  When this happens, atoms pull more strongly on the shared electrons than other atoms do.  As a result the electrons move closer to one atom, causing atoms to have slight electrical charges.  One side of the molecule is slightly negative and the other is slightly positive  Sometimes in covalent bonds there is an unequal sharing of electrons in a molecule.  When this happens, atoms pull more strongly on the shared electrons than other atoms do.  As a result the electrons move closer to one atom, causing atoms to have slight electrical charges.  One side of the molecule is slightly negative and the other is slightly positive

Polar Molecules -Molecules with unequal electron sharing are called polar molecules -Polar molecules have a strong attraction to one another because of their slightly charged sides. -(just like opposite ends of a magnet) -Molecules with unequal electron sharing are called polar molecules -Polar molecules have a strong attraction to one another because of their slightly charged sides. -(just like opposite ends of a magnet)

Are all covalent bonds polar?  Not all covalently bonded elements are polar, only the ones with unequal sharing.  A molecule can be nonpolar if…  it contains positive and negative charges that cancel each other out  Not all covalently bonded elements are polar, only the ones with unequal sharing.  A molecule can be nonpolar if…  it contains positive and negative charges that cancel each other out

A polar molecule Water is a polar molecule and looks like this… Electrons are pulled more towards the nucleus of the oxygen

Polar molecule video

Video notes  The attraction atoms have for electrons varies.  Polar molecules have positive and negative poles like a battery or a magnet.  The attraction atoms have for electrons varies.  Polar molecules have positive and negative poles like a battery or a magnet.

Why does it matter that water is polar?  Water’s charged sides attract other elements and compounds with their charges.  For example: a negative ion like chlorine would be attracted to the positive end of a water molecule (the H or hydrogen side)  Water’s charged sides attract other elements and compounds with their charges.  For example: a negative ion like chlorine would be attracted to the positive end of a water molecule (the H or hydrogen side)

Water the Universal solvent  The polar charge that develops across the water molecule helps make it an excellent solvent.  Solvent- a liquid that allows solids to break apart to become a well mixed solution.  This is why water is called the Universal Solvent.  Water can dissolve more substances than any other liquid  The polar charge that develops across the water molecule helps make it an excellent solvent.  Solvent- a liquid that allows solids to break apart to become a well mixed solution.  This is why water is called the Universal Solvent.  Water can dissolve more substances than any other liquid

Salt (NaCl) dissolved in water Salt contains sodium ions Na + and chlorine ions Cl - Sodium is attracted to oxygen end of H 2 O Chlorine is attracted to hydrogen end of H 2 O this can also be seen on pg 180 of your textbook CLICK HERE FOR SALT WATER ANIMATION