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

2. Scenarios (a) and (b) are chemical contamination
Scenario (c) is biological contamination
Explain how water contaminated from a mine could end up in the ocean 100 miles away.
Make a list of things you do every day that require clean and safe water.
Reflection: Write about some things you and your community regularly do that could threaten the water supply.

3. Title: Mystery Liquids
Activity 35
Title: Mystery Liquids

4. How would you describe the contents of these containers?
Clear
Colorless
Liquid

5. 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.

6. 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.

7. Water Phase Changes

8. 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!

9. Read C-29
Problem: How can physical properties help you identify substances?
Hypothesis/Initial Thoughts:

10. 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

11. 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?

12. 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

13. 97 – 103 ºC 75 – 81 ºC -2 - +2 ºC Not measured
Table 1: Observations of Two Unidentified Liquids
Property
Liquid A
Liquid B
Qualitative Data (observations)
Appearance
Smell
Feel on fingers
Behavior of a drop on plastic
Evaporation
Possible identities
Quantitative data (measurements)
Density
Boiling point
Melting point
97 – 103 ºC
75 – 81 ºC ºC
Not measured
Table 2: Density Calculations
Liquid A
Liquid B
Volume of liquid sample
Mass of graduated cylinder
Mass of cylinder plus liquid
Mass of liquid sample
Density of liquid

14. 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?

15. Some Properties of Five Liquids Shape of a drop on plastic
1. Review the Data Table below:
Some Properties of Five Liquids
Liquid
Water
Methanol
Ethanol
Isopropanol
Acetone
Appearance
Clear
Smell
None
Yes
Shape of a drop on plastic
Round
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)
-94
-117
-90
Undefined

16. Analysis Questions #1 and #2
Substances can be identified based on their properties.
What was Liquid A?
Water
What was Liquid B?
Ethanol

17. Phases of Water Time Temp Description -20 Solid Ice 12 60 Liquid Water
-20
Solid Ice 12 60
Liquid Water 2
Melting Ice 14 80 4 16
100
Boiling Water 6 18 8 20
Water Vapor Gas 10 40 22
120