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.

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.

Title: Mystery Liquids 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

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 -2 - +2 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

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 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

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 -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