Transcript More About Matter - Port Washington School District

More About Matter
Physical vs. Chemical
Properties

Physical Properties

Observed without changing identity of substance.


Ex: color, hardness, density, odor, malleability, ductility, MP temp.
Chemical Properties

Observed during chemical changes

Ex: flammable, explosive, corrosive, rusts, decomposes
Chemical vs. Physical Changes

Physical Change


Does not alter chemical composition.
Substance still has same chemical formula.


Ex: bend, cut, grind, dissolve, undergo a phase change
Chemical Change


Chemical composition changes as a reaction occurs.
New products formed.

Ex: cook food, sour milk, burn wood, explode dynamite
What Type of Change?
What Type of Change?

H2O(s) → H2O(l)

2H2O (l) → 2H2(g) + O2(g)

NaCl(s) → NaCl(aq)

CH4(g) + O2(g) → CO2(g) + H2O(g)
Is it Chemical or Physical?

Sometimes it is possible to determine a
chemical change using the naked eye.

Things to look for:

Gas bubbles produced, unusual color change,
new odor produced, precipitate forms

Precipitate: an insoluble solid that forms
when two solutions are mixed.
Types of Matter
Pure Substance vs. Mixtures
Pure Substances
Elements
•
Made up of atoms of one specific type
•
Have specific physical and chemical properties.
•
Cannot be broken down by chemical reactions
•
Ex: Fe, K, Na, Si
Compounds
Two or more different elements chemically
bonded together.
Have different chemical and physical properties
than elements that make them up.
Definite fixed proportions by mass.
•
Ex: C6H12O6, MgCl2, CO2, NaCl
Mixtures
Mixtures
Two or more pure substances
physically combined.

Mixtures can be solid, liquid or gaseous.
Composition Not Fixed
Composition of a mixture is NOT FIXED.
 Can vary depending on how much of each
component is added.

Retaining Their Properties

Substances in
mixtures retain their
own properties.

Ex: Iron filings (Fe)
and sand (SiO2)

Even if mixed the iron
retains its magnetic
properties
Clips
Mixtures vs. Pure Substances
https://www.youtube.com/watch?v=88MBCyi
aPSM

Types of Mixtures
Homogeneous Mixtures

Components are
distributed uniformly
at the molecular
level.

All true solutions are
homogeneous.

Aqueous = (aq)
dissolved in water or
“in solution”

If you see (aq) it is a
homogeneous mixture

Ex: NaCl (aq)
Heterogeneous Mixtures

Components are
not uniformly
distributed at the
molecular level.

Colloids and
suspensions are
included in this
category.
How to Tell if a True Solution

Tyndall Effect

Suspensions and colloids have larger particles that
will scatter a beam of light. In a true solution the light
will not be scattered
Techniques to Separate
Mixtures
Separating Mixtures

Components retain their own properties,
so use these properties to separate them.

Ex: density, particle size differences, solubility
differences, BP temperature, magnetic properties
Filtration

Ex: Separate water & sand

Can be used to separate
heterogeneous mixtures

Technique cannot be used
to separate components of
solutions
Separatory Funnel

Ex: Separate oil and
water

What type of mixture?
Evaporation

Ex: Separate sugar
from water

What type of mixture?
Chromatography

Solvent runs up paper and
components separate out
along length of paper
depending on level of
attraction to solvent.

Ex: Separate different types
of chlorophyll
Distillation

Separates two or more
liquids, due to
differences in boiling
point temp.

Ex: Separate alcohol
and water

What type of mixture?
Clips
Separating Mixtures
 http://youtu.be/fJXBlfwB_Nw
 Distillation
 http://youtu.be/tcJXGIJA9Wo

Density Calculating
Density

Because all matter has mass and volume, all
matter has density.

No matter the size of the sample, the density
doesn’t change.

It is a physical property.

See Reference Table S for the density of elements.
D
=
M
V
https://www.youtube.com/watch?v=GnBQ6vIutDM
Density of Water

Density of Pure Water = 1.0 g/ml

If a substance has a density greater than water it
will sink, if not it will float.

When you dissolve a substance in water it
makes it more dense.

http://youtu.be/7xGo-HPGKmY
Measuring Density (D = M/V)

Mass


Measured on a
scale, often you
need to use a
weighing dish or a
beaker.
Volume


Can be measured
in different ways.
For solids the
method of water
displacement is
often used.
Density column
 http://youtu.be/-CDkJuo_LYs
 Coke vs Diet coke
 http://youtu.be/5HCmRCGv37s

Cool Clips
Chemical Reactions (Bill Nye)
 http://youtu.be/1MiVyBHQmJk
 http://youtu.be/66kuhJkQCVM
 Steve Spangler (clock reactions)
 http://youtu.be/BqeWpywDuiY
 Diet Coke and Mentos
 http://youtu.be/9vk4_2xboOE
