Transcript Lab #3 - University of San Diego Home Pages

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

Experiment 1
Heat water
to 40oC
Cool water
to 5oC
Hot plate
ice
Add food
coloring to
hot water
using dropper, carefully add
colored hot water to cold water
observe layering
record data
Experiment 2
measure salinity using the refractometer
add food
coloring to
salt water
fresh water
salt water
gently and carefully
transfer salt water
use a dropper or pour
observe layers
record data
Experiment 3
Cool fresh
water to
5oC
ice
Heat salt
water to
40oC
Add food
coloring to
Hot plate
hot salt
water
using dropper, carefully add
colored hot water to cold water
observe layering
record data
Experiment 4
Record observations
red food color
50oC
blue food color
0oC
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
1
5
4
3
2
http://terraserver.microsoft.com/
Pacific
Ocean
Questions to think about for next week:

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?