Transcript Activity 34 Analysis 1. Based on the information from the reading, determine which type of contamination, biological or chemical, is present in the.

Activity 34 Analysis
1. Based on the information from the reading,
determine which type of contamination,
biological or chemical, is present in the following
scenarios. Explain.
a.
b.
c.
Thousands of cars travel on city roads every day. The tires rub
against the road and leave behind small flakes of rubber. When
the brakes are used, tiny amounts of copper flake off. Eventually
the rubber and copper get washed into streams and rivers.
You wash your car with soap in the driveway. Soapy water drains
down the gutter and into the storm drain, and eventually runs into
a river, lake, or bay.
Scientists discovered that droppings from seagulls in a restored
salt march were spreading to shallow ocean waters near a
beach. Officials closed the beach to swimming because the
bacterial contamination was thousands of time higher than the
limit that people could safely be exposed to.
• Scenarios (a) and (b) are chemical
contamination
• Scenario (c) is biological contamination
2.Explain how water contaminated from a
mine could end up in the ocean 100 miles
away.
3.Make a list of things you do every day that
require clean and safe water.
4.Reflection: Write about some things you
and your community regularly do that could
threaten the water supply.
Activity 35
Title: Mystery Liquids
How would you describe the
contents of these containers?
• Clear
• Colorless
• Liquid
What is the difference between
a solid, liquid, and gas?
• Unlike solids, the liquid phase is free flowing
and takes on the shape of its container (as
do gases).
• Like solids (but not gases), liquids “hold
together” and have a definite volume. Gases
expand to fill any container, and have neither
a definite shape nor a volume.
• All substances are made of characteristic
smaller pieces or parts, such as atoms or
molecules.
Comparing Solids, Liquids, and Gases
• The basic particles do not change - only the
arrangement and distance between particles change
during a phase change.
• Phase changes are examples of physical changes.
Water Phase Changes
How would you find out what
the two liquids are?
• Observe or test them more closely.
• Compare the results to known
characteristics of specific liquids.
• Gather Data!
Read C-29
Problem: How can physical properties help
you identify substances?
Hypothesis/Initial Thoughts:
Vocabulary Review:
• What word do we have for data that is
numerical?
– Measurement
– Quantitative data involves descriptions
based on measurements
• What type of data describes
characteristics people can perceive
without making measurements?
– Qualitative data
Qualitative Data (Observations)
• Appearance
– Visually examine the vials
• Smell
– Wave the air above each liquid toward your nose
• Feel on Fingers
– Place one drop on your finger and rub with thumb
• Behavior of a Drop on Plastic
– Try to move the drop with a stir stick on plastic
• Evaporation
– Place a drop on the glass slide. Does it evaporate?
• Possible Identities
– Do you know what it is?
Quantitative Data (Measurements)
• Density
– Use a volume of 3.0 mL for groups 1 & 8
• 4.0 mL for groups 2 & 7
• 5.0 mL for groups 3 & 6
• 6.0 mL for groups 4 & 5
– Mass the empty cylinder and subtract that from the
cylinder with the liquid
– Density = mass/Volume
• Boiling Point
– Demonstration
• Melting Point
– Demonstration
Table 1: Observations of Two Unidentified Liquids
Property
Liquid A
Qualitative Data (observations)
Appearance
Liquid B
Smell
Feel on fingers
Behavior of a drop on plastic
Evaporation
Possible identities
Quantitative data (measurements)
Density
Boiling point
97 – 103 ºC
Melting point
-2 - +2 ºC
75 – 81 ºC
Not measured
Possible identities
Table 2: Density Calculations
Liquid A
Volume of liquid sample
Mass of graduated cylinder
Mass of cylinder plus liquid
Mass of liquid sample
Density of liquid
Liquid B
Density
• Compare densities for Liquids A and B
• Does the amount of liquid change the
density?
• When more liquid is added to the graduated
cylinder, what happens to the volume?
• To the mass?
• If you pour some out, what happens?
• If you double the volume, what happens to
the mass?
1. Review the Data Table below:
Some Properties of Five Liquids
Liquid
Water
Methanol
Ethanol
Isopropanol
Acetone
Appearance
Clear
Clear
Clear
Clear
Clear
Smell
None
Yes
Yes
Yes
Yes
Shape of a drop on plastic
Round
Flat
Flat
Flat
Flat
Density (g/mL)
1.000
0.791
0.789
0.786
0.790
Boiling Point (ºC)
100
65
78
82
56
Melting Point (ºC)
0
-94
-117
-90
Undefined
Analysis Questions #1 and #2
• Substances can be identified based on
their properties.
• What was Liquid A?
– Water
• What was Liquid B?
– Ethanol
Phases of Water
Time Temp
Description
Time Temp
Description
0
-20
Solid Ice
12
60
Liquid Water
2
0
Melting Ice
14
80
Liquid Water
4
0
Melting Ice
16
100
Boiling Water
6
0
Melting Ice
18
100
Boiling Water
8
20
Liquid Water
20
100
Water Vapor Gas
10
40
Liquid Water
22
120
Water Vapor Gas