One substance all living things require Water One substance all living things require Unique properties due to polar shape Polar = opposite charges at opposite ends of molecule like a little magnet Attracts to opposite charges 3.1 Water pp. 49-51 What strange things have you noticed about water?

The abundance of water is the main reason the Earth is habitable 3.1 Water pp. 49-51 Most cells are surrounded by water, and cells themselves are about 70–95% water The abundance of water is the main reason the Earth is habitable Overview: The Molecule That Supports All of Life

Fig. 3-1 Figure 3.1 Why does the abundance of water allow life to exist on the planet Earth?

Cohesion = water sticking to other water molecules 3.1 Water pp. 49-51 Hydrogen Bonding = weak attractive force between positive and negative ends of a water molecule. Water is “sticky” Cohesion = water sticking to other water molecules Adhesion = water sticking to other substances Water on skin Capillary action

Fig. 3-4 Figure 3.4 Walking on water

Hydrogen bond H O H  –  +  –  +  –  +  –  + —— —— Fig. 3-2 Figure 3.2 Hydrogen bonds between water molecules  –  +

Hydrogen bonds are stable Liquid water Fig. 3-6 Hydrogen bond Ice Hydrogen bonds are stable Figure 3.6 Ice: crystalline structure and floating barrier Liquid water Hydrogen bonds break and re-form

Water is very good at absorbing heat energy. 3.1 Water pp. 49-51 Water is very good at absorbing heat energy. Do you feel hotter or cooler around water?

San Bernardino Burbank Santa Barbara 73° 100° 90° Riverside 96° Fig. 3-5 San Bernardino 100° Burbank 90° Santa Barbara 73° Riverside 96° Los Angeles (Airport) 75° Santa Ana 84° Palm Springs 106° 70s (°F) 80s Pacific Ocean 90s 100s Figure 3.5 The effect of a large body of water on climate San Diego 72° 40 miles