unit 2: water - dr. g's chemistry...an element c. a heterogeneous mixture d. a homogeneous...
Post on 24-Mar-2020
6 Views
Preview:
TRANSCRIPT
MatterAnything that has mass and
volume (occupies space)
PURE SUBSTANCES
- Each sample __________=
pure!
- Each piece has exact same make-
up (____________)
MIXTURES
- ____________________
________combined but
__________________
- _______________from
sample to sample
Cannot be separated by
physical means
Can be separated by physical
means
I. CLASSIFICATION OF MATTER
looks the same
fixed composition
2 or more different pure
substances
not chemically bonded together
Composition can vary
PURE SUBSTANCE
Element
(made up of ____________)
Two kinds of elements:
1. Monoatomic =
ex:
2. Diatomic =
ex:
Compound
(____________________
_________________)
Two types:
1. Ionic=Metal + nonmetal
ex:
2. Molecular/Covalent= nonmetal
+nonmetal
ex:
Cannot be separated by
chemical means
Can be separated by
chemical means
1 type of atom
one atom
Na2 atoms
Cl2
H2O (water)
NaCl (table salt)
2 or more different elements
chemically combined
MIXTURES
Homogeneous
(evenly mixed, distinct pattern)
Words to look for:
Ex:
**
Heterogeneous
(______________, no
pattern)
Hints to look for: 2 different
phases that don’t blend together
Ex:
**
Same composition
throughout
Different composition
throughout
solution, aqueous (aq),
dissolved in water
Salt water, iced tea
Homo = same
not evenly mixed
Sand and water,
cereal, trail mix
Hetero = unlike
PRACTICE1. A compound differs from an element in that a compound
a. Is a pure substance
b. Has a definite composition
c. Has a definite melting point
d. Can be decomposed by a chemical reaction
*Hint: Decomposed means ___________
2. Which of the following substances cannot be separated by chemical change?
a. Nitrogen (g)
b. Sodium chloride (s)
c. Carbon dioxide (g)
d. Magnesium Sulfate (aq)
*Hint: If it _____________by a physical OR chemical change it must be an ________. An
element is as simple as it gets so it can’t be broken down at all!
broken down
can’t be separated element
3. A pure substance that is composed only of identical atoms is classified as a
a. A compound
b. An element
c. A heterogeneous mixture
d. A homogeneous mixture
4. An example of a homogenous mixture is
a. Iron pieces in water
b. Kool Aid
c. Soup
d. Sand and Water
*Hint: If it appears to be one substance, it’s a ___________ mixture. If you can see
two or more different parts, it’s a ___________mixture.
homogenous
heterogeneous
II. REPRESENTING MATTER
1. Chemical Symbols and Formulas
A. Elements vs. Compounds
• Element = formula that contains ___________(note: a symbol is represented by a capital
letter)
• Compound = formula which contains ______________________
Examples:
Circle all the elements and underline the compounds below. Then, on the line provided, record the
number of different types of symbols within the species.
LiCl __ Mg __ NaOH ___ H2 __
Questions:
1. Does each compound have the same number of different types of symbols? ____
2. For each ELEMENT above, how many different types of symbols are there?__
3. What is the minimum number of different symbols that must be present in order for a species to be
considered a compound? __
*Hint – one capital letter = one element!
2 1 1
No
3
1
2
only one symbol
2+ different symbols/elements
B. Understanding Compound Formulas:
• Within a compound, you may see subscripts. These subscripts tell you the number of each type of atom that is present.
Example: CO2
# carbon atoms __ # oxygen atoms __
• If there are parentheses present around two or more atoms, the subscript applies to all atoms within the parentheses.
Example: Al(CN)3
# aluminum atoms __ # carbon atoms __ # nitrogen atoms __
1 2
1 3 3
• If one of the atoms within the parentheses has a subscript, you multiply this number by the number
outside of the parentheses.
Example: Fe2(SO4)3
# iron atoms __ # sulfur atoms __ # oxygen atoms ___
• Sometimes when you look at a chemical equation you will see a number IN FRONT OF a molecule.
That number tells how many there are of the entire molecule.
Example: 3H2O means that I have 3 molecules of H2O. Therefore it contains:
# hydrogen atoms (H) ___
# oxygen atoms (O) ___
2 3 12
6
3
C. Understanding Element Formulas
• The Common Elements—see periodic table!
• Rules for writing element symbols:
1) 1st letter is always capitalized.
2) If a second letter exists, it is lower case.
Example: Ca, C, Be, B --- Never CA or cA
**Warning: Be careful not to get tricked! Bi is the symbol for the element Bismuth. BI3
is the formula for Boron Triiodide, a compound containing the elements boron and
iodine. The capital letter is the clue that it is a different element!
Now that you know what a compound is and
what it looks like, let’s look at water again
and see why it is a compound.
1. What is the chemical formula for water?
2. Is water a pure substance or mixture?
Water is a pure substance because water has a fixed composition. It does not vary. Water is always H2O
3. Why, out of the two types of pure substances, is water a compound?
Water is a compound because it is made up of two or more different elements (hydrogen and oxygen) chemically bonded together
2. Particle Diagrams
• A particle diagram is a visual representation of the particles of a substance, with the particles typically
represented as circles.
• Different colors/shapes represent atoms of different elements. A key is used to identify the different
elements.
A single element Diatomic element (2
of same circle) Compound (2 or
more DIFFERENT
circles touching)
Key:
=Na (sodium)
= Cl (chlorine)
2 atoms of Na
Atom - one circle Molecule - two or more
circles
Mixture
(combination of
atoms/molecules)
2 molecules of
Cl2
2 molecules of
NaCl
Mixture of all
three
**Particle Diagrams:
https://www.youtube.com/watch?v=HzO_rUGj2zE
Practice
1. Which particle diagram(s) represent a mixture?
*Hint – for a ________, look for ___________________________mixed together
2. Which particle diagram(s) represent a pure substance?
*Hint – for a ___________, look for a diagram that is pure or in other words, _______________!
mixture 2 or more different types of particles
pure substance only has 1 type of particle
3. Which of the following particle diagrams represents a mixture of one compound and
one element?
4. Which particle diagram represents a diatomic element?
III. PROPERTIES OF MATTERA. Physical properties are the constants about a substance; can use our senses
to observe them; _________________________________
Examples:
B. Chemical properties are behaviors of a substance when it undergoes a
chemical change or reaction: _____________________________
Examples:
can be measured or observed without changing the substance
melting point, color, texture, density
describes the ability to change into a new substance
Flammability, reactivity
Practice
Identify the following as a physical (P) or chemical (C) property.
_____P_____ 1. The mass of copper wire is 255 g.
_____P_____ 2. The boiling point of ethyl alcohol is 77°C.
_____C_____ 3. Baking soda reacts with vinegar to make carbon dioxide
gas.
_____P_____ 4. The density of mercury is 13.6g/mL.
_____P_____ 5. The solubility of sodium chloride in water is 40g/100mL of
water
*Hint – for chemical properties, look for the word ______react!
Now that you know the difference between a
physical and chemical property, identify the
following properties of water as physical (P) or
chemical (C)
1. Water’s boiling point is 100 °C
2. Water dissolves a variety of substances
3. Water is cohesive, meaning its particles like to stick
together
4. Water reacts violently with certain metals like sodium
and cesium
P
P
P
C
IV. CHANGES IN MATTER• Matter is always changing. Ice in your drink melts. Wood in your fire burns. There are
two main types of changes in matter:
A. Physical Change – a change that does NOT change the chemical make-up of
a substance; ____________________________
*PHYSICAL changes can be reversed easily
Examples: melting, boiling, dissolving
*Hint – look for ____________ or changes in size or shape
appearance affected but not composition
phase changes
B. Chemical Change – a change in which the composition of a substance is
changed;_______________________________
*chemical changes are difficult to reverse
Examples: rusting, burning, any signs of a chemical reaction*
*recall the signs of a chemical reaction
1. _________– be careful! Not just to a lighter color like red to light red but like
red to yellow!
2. _____________– seen through ______________
3. Energy produced or consumed— in form of heat (__________), light, etc.
4. __________________(a solid in a solution)
new substance(s) formed with new properties
Color change
Gas is produced bubbling/fizzing
change in temp
Formation of a precipitate
Changes in Matter…Physical or Chemical?
Burning Toast Chemical
Making Ice Cubes Physical-can reverse by melting
Lighting a Candle Chemical
Spoiling Milk Chemical
Making Kool-Aid Physical-can reverse by evaporating water off
Practice
*Hint – ask yourself, does the change make a new substance with a new
composition? If it does, it’s a _______________. If the substance just
looks different but still has the same composition, it’s a _______________
chemical change
physical change
Now that you know the difference between a
physical and chemical change, identify the
following changes in water as physical (P) or
chemical (C)
1. Water reacting with sodium metal to produce a base and
hydrogen gas
2. Water dissolving sugar to make sugar water
3. Ice melting into liquid water
4. Water boiling into a gas
5. Water decomposing into hydrogen and oxygen
C
P
P
C
P
V. PHASES OF MATTER
• Matter exists in three phases or states
State of
Matter
Shape Volume Density Particle
Diagram
Solid (s) _______ Shape ______ volume High
Liquid (l) No definite shape-
___________
________
______ volume Medium
Gas (g) No definite shape
– _________
________
No definite volume
– ________
________
Low
*Hint – definite means fixed. It doesn’t change no matter what it’s in
Definite Definite
Definite
takes shape of
container
takes shape of
containerexpands to fill
container
THINK ABOUT THIS
What happens to the spacing and speed of particles at each of the
phases?
SOLID LIQUID GAS
https://www.brainpop.com/science/matterandchemistry/matterchangingstates/
VI. PHASE CHANGES
• A phase change is an example of a ________ change.
• Substances change phases by _____________________
• The motion or _____ of the molecules determines states of matter
• The more _______ molecules have, the _______ they move!
physical
absorbing or releasing energy
speed
energy faster
melting
boiling
Note: **__________________are two substances that readily sublime, or readily undergo
sublimation, at room temperature
https://www.youtube.com/watch?v=PaOFohqjZ1s
s g
freezing
condensation
CO2(s) (Dry ice) and I2(s)
Practice:
1. What is another name for boiling?
2. In what phase do the molecules have the most energy?
3. What is the temperature (in Celsius) that water starts to melt? ____ Label where this would be on
the diagram above.
4. What is the temperature (in Celsius) that water starts to boil? _____ Label where this would be
on the diagram above.
Evaporating/vaporization
gas
O°C
10O°C
Boiling point
Melting point
VII. SEPARATING MATTER
•Certain types of matter can be separated using various methods.
o _________________________________.They
cannot be separated at all
o ________can only be separated ________
o ________can be separated _________
•Physical separation = separating matter based on ___________
o ___________________of the substances being separated
•Chemical separation = separating matter through ___________
o _________________of the substances being separated.
Elements cannot be separated physically or chemically
Compounds chemically.
Mixtures physically
Doesn’t change the make-up
Changes the make-up
physical properties
a chemical change
Examples of Separation Techniques
Separation Apparatus Type of Separation
(Physical or
Chemical)
Description of
Technique
What types of matter will
it separate?
Tweezers
Sifting
Magnet
Physical
Physical
Physical
Separates mixtures
based on different
shape/size particles
Heterogeneous mixtures
(or things in different
phases)
Ex: Salad
Separates mixtures
based on different
shape/size particles
Heterogeneous
mixtures (or things in
different phases)
Ex: Sand and Rocks
Separates mixtures
based on magnetic
properties
Heterogeneous Mixtures (or
things in different phases)
Ex: Iron and Sand
Warning: not all metals are
magnetic
Examples of Separation Techniques
Separation Apparatus Type of Separation
(Physical or
Chemical)
Description of
Technique
What types of matter will
it separate?
Filtration
Evaporation
Physical
Physical
Separates mixtures
based on different
shape/size particles
Separates mixtures
based on different
boiling points
Heterogeneous
mixtures (or things in
different phases)
Ex: Sand and Water
Homogenous mixtures
(solutions, things
dissolved in water)
Ex: Salt Water!
Examples of Separation Techniques
Separation Apparatus Type of Separation
(Physical or
Chemical)
Description of
Technique
What types of matter will
it separate?
Distillation
Chromatography
Physical
Separates mixtures
based on different
boiling points
*it’s basically fancy
evaporation!
Homogenous mixtures
(solutions, things
dissolved in water)
Ex: Sugar and water
Physical
Separates mixtures
based on different
particle size and
solubility
Homogenous mixtures
(solutions, things
dissolved in water)
Ex: Different colored dyes
in ink
• What do you notice about the type of separation for all these techniques?
• What do you notice about the types of matter that these techniques can separate?
• What is the main difference between compounds and mixtures that makes mixtures
able to be separated physically but not compounds?
• Can you separate salt water using filtration?
– Why or why not?
All physical separation
Only mixtures
Mixtures have 2 or more substances only physically combined; compounds are 2
or more things chemically bonded together
NOBecause salt dissolves in water so it would go right
through the filter with the water. Salt water is a
homogenous mixture!
QUESTIONS
top related