Week 3 Relative density and convection Objective: –to become familiar with the effects of relative density on convection –to recognize how convection influences ocean circulation –to measure temperature and salinity in seawater

Focus questions to be discussed after experiments are completed What is density? What is convection? What is the relationship between relative density and convection? Which earth materials (air, water, rocks) convect? How does convection influence weather? Ocean circulation? Earth’s crust and mantle? What happens to the process of convection under low gravity conditions (for example inside the space shuttle in space)? Why?

Density Mass per unit Volume –Determined by temperature and salinity –Density of seawater increases all the way to its freezing point of -1.9 º C

Your job Work in teams Work though the experiments Keep accurate lab notes Participate in small group discussion and large group presentation

Hot plate Heat water to 40 o C ice Cool water to 5 o C Add food coloring to hot water using dropper, carefully add colored hot water to cold water observe layering record data Experiment 1

fresh watersalt water gently and carefully transfer salt water use a dropper or pour observe layers record data measure salinity using the refractometer add food coloring to salt water Experiment 2

Hot plate Heat salt water to 40 o C ice Cool fresh water to 5 o C Add food coloring to hot salt water using dropper, carefully add colored hot water to cold water observe layering record data Experiment 3

Experiment 4 red food color blue food color 50 o C 0oC0oC Record observations

Focus questions to be discussed after experiments are completed What is density? What is convection? What is the relationship between relative density and convection? Which earth materials (air, water, rocks) convect? How does convection influence weather? Ocean circulation? Earth’s crust and mantle? What happens to the process of convection under low gravity conditions (for example inside the space shuttle in space)? Why?

Science magazine July 2005 What is THERMOHALINE circulation?

Preparation for field trips Next week during lab time: –San Diego River channel Carpools! Reminder: Lab Quiz March 7

Logistics San Diego River trip Bring –Note book and pen –Jacket or sweatshirt –Sturdy walking shoes Meet in ST 175 promptly at 2:30

San Diego River field trip

San Diego River Pacific Ocean

What are two sources of water in the river channel? Which is denser? Which direction is the water flowing on a rising tide? Ebbing tide? Is ocean water likely to flow underneath or on top of river water? Why? How might differences in salinity and temperature influence the ability of plants and animals to live in the river habitat? Questions to think about for next week: