# A look at Water and Its Contaminants Part 2

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A look at Water and Its Contaminants Part 2

Let's calculate the density for each of these blocks.
Block I Mass = 79.4 grams Volume=29.8 cubic cm. Block II: Mass= 25.4 grams Write these figures down!!!!

Remember Density= Mass/Volume
Density of Block 1 = Density of Block 2 = 2.66 g/cm3 0.85 g/cm3

Density of a Solid What is each block made of? Block 1 = Block 2 =
Using the table below it is now possible for you to determine what substance makes up each block. The densities for some common substances are: Substance Density (gm/cu.cm) Air Wood (oak) Water Ice Aluminum 2.7 Lead Gold Ethanol Methanol Block 1 = Block 2 = Aluminum Wood

Density of a Liquid Problem: You are given two unknown liquids. Find the density of each. Materials: 100ml graduated cylinder, triple beam balance, calculator, 2 unknown liquids. Procedure: 1) Find the mass of the empty graduated cylinder. 2) Pour unknown liquid #1 into the graduated cylinder to the 50 ml. level. 3) Find the mass of the graduated cylinder with 50ml of unknown liquid #1. 4) Repeat steps 1-3 for unknown liquid #2.

Density of a Liquid We can calculate density of a liquid using the formula: Density= Mass/Volume where mass is that for just the liquid (you must subtract out the mass of the graduated cylinder). Now let's calculate the densities of the two liquids using the following given data.

Density of a Liquid Liquid #1:
Given: Mass of empty graduated cylinder = 78 grams Mass of graduated cylinder with unknown liquid #1= 128 grams. Find: a) Mass of just the liquid = ____ b) Volume of liquid=_____ c) Density of liquid #1 =____ 50 grams 50 ml 1.00 g/ml

Density of a Liquid Liquid #2:
Given: Mass of empty graduated cylinder = 78 grams Mass of graduated cylinder with unknown liquid #2= grams. Find: a) Mass of just the liquid = ____ b) Volume of liquid =_____ c) Density of liquid #2=____ 39.5 grams 50 ml 0.79 g/ml

Density of a Liquid What is each liquid?
Using the table below it is now possible for you to determine what each liquid is. Densities for some common liquids are: Substance Density (gm/cu.cm) Water Cooking oil Sea Water Carbon tetrachloride Benzene Glycerin Methanol Liquid 1= Liquid 2= Water Methanol

Density Lab Class Data

Density Lab Class Data & Average
Water Density is 1.00 g/cm 3 Ethanol Density is g/cm 3

Density Lab Was your experimental value the same as the actual value?
What is the percentage error?

Percentage Error Water Density Percentage Error Average = 10% Alcohol Density Percentage Error Average = -4.56%

Predict Based on the Densities of the two elements, what order would you expect them to be in placed in the same container. Add a color to the water and then pore them in the order you expect. Were you correct? Why or Why not?

Density Demonstration
Ice Cube and Ethanol vs Ice Cube and Water

Mixtures and Solutions

Mixture Video

Mixtures and Solutions
A mixture where two or more substances are mixed together but are not chemically combined is called as an heterogeneous mixture.

Mixtures and Solutions
A homogeneous mixture has the same uniform appearance and composition throughout. Many homogeneous mixtures are commonly referred to as solutions.

Mini Lab: Sand Under a Microscope
Look at the different types of sand under the microscope. Draw a sketch of what you see under the microscope. Is sand a heterogeneous or homogeneous mixture. Explain Why? Do these samples come from the same place? Explain.

Mixtures and Solutions
Colloids are mixtures whose particles are larger than the size of a molecule but smaller than particles that can be seen with the naked eye.

Mixtures and Solutions
A suspension is a type of mixture where the particles are large enough to settle out and can be separated by using a filter.

Mixtures and Solutions

Review What is a Colloid? What is a Suspension? What is a True Solution?

Some Definitions A solution is a _______________ mixture of 2 or more substances in a single phase. One constituent is usually regarded as the SOLVENT and the others as SOLUTES. WELL MIXED

Parts of a Solution SOLUTE – the part of a solution that is being dissolved (usually the lesser amount) SOLVENT – the part of a solution that dissolves the solute (usually the greater amount) Solute + Solvent = Solution Solute Solvent Example solid liquid gas Brass (Zn and Cu) Ocean Water (Na and H2O) Antifreeze (Ethylene glycol in water) Soda Water (CO2 in water) Air (O2 and N2)

Molecular View of Water
What did you observe in this video. To understand this we need to study water at the molecular level.

Molecular View of Water
What are Atoms? Building Blocks of Matter What is an Element? All matter with the same atoms Water is not an element. Is it a mixture? In fact it’s a compound. What is a compound? A compound is two or more elements linked together chemically in fixed proportions. Why is Water represented as having a V shape? Why not Linear? Does it Make a Difference?

Macroscopic vs. Particulate level view of world
Pure Substances – either elements or compounds Elements – on periodic table. Made of only 1 kind of atom (building block of matter), shown by a chemical symbol like H Compounds – made of elements held together by a chemical bond; smallest particle is a molecule, shown by a chemical formula like H2O. Models - representations of concepts

Models of homogeneous vs heterogeneous

Which one shows a homogeneous mixture?