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 Volume=29.8 cubic cm.

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 SolidWhat is each block made of?

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 0.0013Wood (oak) 0.85Water 1.00Ice 0.93Aluminum 2.7Lead 11.3Gold 19.3Ethanol 0.94Methanol 0.79

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= 117.5 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 LiquidWhat 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 1.00Cooking oil 0.92Sea Water 1.025Carbon tetrachloride 1.58Benzene 0.87 Glycerin 1.26 Methanol 0.79

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 0.789 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 ErrorAverage = -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

http://www.youtube.com/watch?v=nxRGahK7B48

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 DefinitionsA 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 solid

solid liquid

liquid liquid

gas liquid

gas gas

Brass (Zn and Cu)

Ocean Water (Na and H2O)

Soda Water (CO2 in water)

Antifreeze (Ethylene glycol 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 WaterWhat are Atoms?Building Blocks of MatterWhat is an Element?All matter with the same atomsWater 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

Homogeneous Heterogeneous

Which one shows a homogeneous mixture?

 

Modeling Matter

• Read pages 27-28• In your Science Notebook Answer Questions

1-8.