5.6 Characteristic Properties

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Physical and chemical properties may be intensive or extensive.

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Characteristic Properties

are...



properties that do not

change with changes in

mass or volume



examples include:



density



boiling point



melting point

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Characteristic Properties



Are properties of a

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characteristic properties

are unique to substances

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Substance State Color Melting Point (C°)

Boiling Point (C°)

Density (g/cm3₎

Oxygen O₂ Gas Colorless -218 -183 0.0014 Mercury Hg Liquid

Silvery-white

-39 357 13.5

Bromine Br₂ Liquid Red-brown -7 59 3.12

Water H₂O Liquid Colorless 0 100 1.00

Sodium Chloride

NaCl Solid White 801 1413 2.17

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Solid

Liquid

Gas

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Bromine

Gas (Vapor)

Liquid

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DENSITY

- an important and useful Characteristic Physical Property

Density



mass (g)

volume (cm3)

Mercury

13.6 g/cm3 21.5 g/cm3

Aluminum

2.7 g/cm3

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Units for Density

Mass is measured in Grams (or related term)

Volume is measured in Litres

Density is a combination of terms

g/L

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lecturePLUS Timberlake 16

Density

Density compares the mass of an object to its volume

D = mass = g or g volume mL cm3

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Density Calculations

M

D V

Cover up whatever unit you are solving for, the two units remaining will show you how

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Learning Check D1

Osmium is a very dense metal. What is its

density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22cm3?

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Solution

2) Placing the mass and volume of the osmium metal into the density setup, we obtain

D = mass = 50.00 g = volume 2.22 cm3

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Volume Displacement

A solid displaces a matching volume of water when the solid is placed in water.

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Learning Check

What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a

graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3

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Solution

2) 6 g/cm3

Volume (mL) of water displaced

= 33 mL - 25 mL = 8 mL Volume of metal (cm3)

= 8 mL x 1 cm3 = 8 cm3 1 mL

Density of metal =

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Learning Check3

Which diagram represents the liquid layers in the cylinder?

(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL)

1) 2) 3)

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Solution

(K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL)

1)

K W

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Density Connections

Mass

Volume

kg L

g mL (cm3)

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To find the density

1- Find the mass of the object

2- Find the volume of the object

3- Divide Density = Mass

Volume

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Problem A piece of copper has a mass of

57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

Density



mass (g)

volume (cm3)

M

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Strategy

1. Get dimensions in common units.

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SOLUTION

1. Get dimensions in common units.

2. Calculate volume in cubic centimeters.

3. Calculate the density.

0.95 mm • 1cm

10 mm = 0.095 cm

57.54 g

6.4 cm3 = 9.0 g / cm

3

(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3

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Worksheet

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Characteristic Property:

Day 2

Melting Point

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Melting and boiling

The melting point is the temperature at which a substance changes from a

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Melting and boiling

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Melting and boiling points of common substances

Materials have a wide range of

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Notice temperature is constant while ice melts!

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The Melting Point

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The Melting Point

Why?

Salt causes the ice to melt faster.

Salt (and other substances) lowers the freezing point of water -- the water has to be colder to freeze

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The Unusual

Behavior

of water of

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Water



A water molecule (H

₂

O), is

made up of

three

atoms

---one

oxygen

and two

hydrogen

.

H

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Hydrogen Bonding

Polarity means small

negative charge at O end

Small positive charge at H end

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– When water reaches 0oC, water becomes locked into a crystalline lattice with each molecule bonded to the maximum of four partners.

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– As ice starts to melt, some of the hydrogen bonds break and some water molecules can slip closer together than they can while in the ice state.

– Ice is about 10% less dense than water at 4oC.

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The Tip of the Iceberg

Which is less dense - water or ice?

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Density of Water

Most dense at 4oC

Contracts until 4oC

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The Density of Water

1. Prevents water from freezing from the bottom up.

2. Ice forms on the surface first—the freezing of the water releases heat to the water

below creating insulation.

3. Makes transition

between seasons

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Welcome to the Wonderful

World of Science

Homework:

Prepare your prelab