DO NOW 10/2

• Turn in your completed video worksheet to the bin

• On page 28 in your notebook, prepare for your Do Now questions

#3

Properties of Water

Today 1/20…

• Pick up your journal

• Keep out lab from yesterday so we can go over questions

• Answer these questions in journal:

– What is the chemical formula for water?

– What does a water molecule look like?

– Why is water so important to life?

Water

• Most important chemical compound in the living world:

– 70-90% of an organism consists of water

• 2 Hydrogen (H) and 1 Oxygen (O) connected by covalent bonds

– H2O

Polar

• O is negatively charged, H is positively charged leading to the “magnet-like” behavior of water molecules

• Mickey Mouse Molecule

– Ears are +

– Chin is -

Hydrogen Bonds

• Water molecules attract each other

• Very weak hydrostatic attractions, called Hydrogen Bonds (formed between water molecules)

STOP AND JOT

• What does it mean to be a polar molecule?

• What are hydrogen bonds (use polarity as part of your answer)?

Water properties:▪Water is called “Universal

solvent”: dissolves many other

substances due to polarity

▪Differences in charges

pulls/pushes substances apart

▪ Water exhibits evaporative

cooling: removes heat when it

evaporates from a surface

▪Ex: sweating cools skin

▪ High Specific Heat- it takes a

lot of heat to it to make it get hot

▪Ex. Regulates extremes in

environment (pond water doesn’t

change temperature b/w night

and day)

Properties of Water Cont…

• Cohesion: attraction of water molecules to each other (sticks to itself)– Ex. Some insects can “walk” on

water

• Adhesion: attraction of H2O to other polar molecules (sticks to other polar molecules)– Ex. Capillary action- pulls

column of water up to the top of water

• Surface tension: skin-like behavior of water surfaces (water on top of a penny)

Properties of Water Cont…

How on earth is this ant pushing a water droplet?!

And why does this drop stick to the leaf and grow larger?

Properties of Water Cont…

• Expansion when it freezes

– Ice floats because it is less dense

– Insulation of ponds in winter

https://www.youtube.com/watch?v=UukRgqzk-KE

Today:

• Properties of Water Activities!

• For more on water watch this crash course tutorial: https://www.youtube.com/watch?v=HVT3Y3_gHGg&feature=share