Activity 34 Analysis1. Based on the information from the reading,

determine which type of contamination, biological or chemical, is present in the following scenarios. Explain.

a. 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.

b. 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.

c. 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.

Title: Mystery Liquids

Activity 35

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

Property Liquid A Liquid BQualitative Data (observations)Appearance    

Smell    

Feel on fingers    

Behavior of a drop on plastic   

 

Evaporation   

 

Possible identities    

Quantitative data (measurements)

Density    

Boiling point    

Melting point    

Possible identities    

  Liquid A Liquid B

Volume of liquid sample    

Mass of graduated cylinder    

Mass of cylinder plus liquid    

Mass of liquid sample    

Density of liquid    

Table 2: Density Calculations

Table 1: Observations of Two Unidentified Liquids

97 – 103 ºC 75 – 81 ºC

-2 - +2 ºC Not measured

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?

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

1. Review the Data Table below:

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 WaterTime 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