Lap #2 Matter and Change Chapter 2
Essential Question:
How does the study of matter help us understand the world around us?
2.1 Properties of Matter
A. Properties: describe matter
Extensive properties
Depends on the amount of matter
Mass: amount of matter
Volume: how much space it occupies
Intensive properties
Depends on type of matter, not how much
Examples: color, hardness, texture, state
Sample photo
Extensive = volume is 125 mL
Intensive = black color, liquid
B. Identifying Substances
Substance: matter with a uniform and definite composition
Every sample of a given substance has identical intensive properties b/c it has identical
composition
Intensive properties can identify a substance
Example: Copper vs Gold
Color
Hardness
Conduction of heat/electricity
Malleability
Physical property: quality or condition of a substance that can be observed or measured
without changing the substance's composition
Can be used to identify a substance
What would be a colorless liquid that boils at 78 degrees C?
What would be a colorless liquid that boils at 100 degrees C?
C. States of Matter
Physical properties include
3 states of matter: Solid, liquid, gas
Solid
Shape and volume fixed
Shape does not depend on shape of container
Volume does not depend on container
Particles are packed tightly, fixed arrangement
incompressible (difficult to squeeze into smaller volume)
expand only slightly when heated
Liquid
Shape matches that of container
Volume is fixed
Particles are in close contact, but not in fixed arrangement
Particles flow and move freely from one location to another
almost incompressible, but expand slightly when heated
Gas
Shape matches container
Volume expands to fill container
Particles are far apart and move quickly
Easily compressed into smaller volume and easily expands Ex: hot air balloons
Gas = substance that is gas state at room temp, for ex. oxygen gas
Vapor = substance that is solid/liquid at room temp, for ex. water vapor
SOLID
VOLUME
SHAPE
ARRANGEMENT OF
PARTICLES
MOTION OF
PARTICLES
LIQUID
GAS
A. Physical vs. Chemical Changes
Physical Changes
Def: During physical change, some properties of a material
change, but the composition does not change
Separating mixtures does not change their composition
Ex: Separate iron filings from sulfur using a magnet
Changing state of matter does not change the substance
Ex: H2O liquid changes to H2O vapor: it is still water
Physical changes can be:
Reversible
Freeze, melt, boil, condense
Irreversible
Cut, grind, crush
2.1 Section Assessment
1. Explain why all samples of a given substance have the same intensive properties.
2. In what way are liquids and gases alike?
In what way are liquids and gases different?
3. Is the freezing of mercury a reversible or irreversible physical change? Explain.
4. Explain why samples of gold and copper can have the same extensive properties, but not the
same intensive properties.
5. Explain why sharpening a pencil is a different type of physical change than freezing water to
make ice cubes.
6. If the state of a substance can change when it is heated or cooled, what does it mean to say
that a certain substance is a solid, liquid or gas?
7. Page 43: Properties of spider silk: stronger than steel, more elastic than nylon, and tougher
than rubber. Biotechnology: transfer spider genes into ____________, who produce milk
containing spider silk.
Classifying Matter Activity
1. Add 1/2 cup tap water to each of four labeled beakers.
2. Without stirring, add 1/2 teaspoon of each solid to the corresponding, labeled beaker.
3. Observe and record any change that occurs after the solids are added in the table.
4. Stir the contents of each container for at least 45 seconds.
5. Record what you observe after stirring, in the table.
Before stirring
After stirring
Powdered Sugar & H20
Flour & H2O
Baking soda & H2O
Baking powder & H2O
1. When you measured 1/2 teaspoon of each solid, were you measuring mass or volume?
____________________ Is that an intensive property or an extensive property?
____________________ Does a measurement such as 1/2 teaspoon identify the substance
measured? _________
2. What physical properties do all four substances have in common?
___________________________________________________________
3. Which solid could you distinguish from the other three after Step 2?
_______________________________
Which states of matter did you observe after this solid was added to water?
_______________________________________ Do you think the substance changed its state,
or do you think a chemical change occurred? ___________
4. Can you distinguish completely among the remaining three solids based on the results of
Step 4? Explain.
______________________________________________________________________________
______________________________________________________________________________
Baking soda vs. Baking powder
Both are chemical leavening agents: they react with other ingredients to produce CO2 gas
which is trapped in batters and doughs to make baked goods light and fluffy instead of dense
and heavy.
Baking Soda = Sodium Bicarbonate = NaHCO3
an alkaline compound that needs an acid in the ingredients plus water to react, e.g.
buttermilk, sour cream, yogurt, lemon juice, cocoa powder
it reacts quickly, so can't let ingredients sit around too long before baking
test for freshness by mixing w/vinegar (volcano eruption experiment)
add too much: metallic flavor
4 times stronger than baking powder: 1/4 tsp will leaven 1 cup flour
Baking Powder = Baking Soda plus starch plus two acids
contains the alkaline baking soda and already has acid in it, so doesn't
need an acid in other ingredients; just needs moisture plus heat
double acting: reacts in presence of liquid and when heated in oven
can make doughs and batters ahead of time
Recipes that call for both together leaven well, produce light and airy
baked goods
Test for freshness: should bubble up when added to hot H2O
Baking soda will produce denser more chewy cookies
Baking powder will produce cake-like, puffy cookies
2.2 Mixtures
A. All Matter is either:
Substance or a mixture
B. Classifying mixtures
Mixture= physical blend of two or more components
Most samples are mixtures
2 types
Heterogeneous mixture
Homogeneous mixture
Heterogeneous mixture
Composition is not uniform throughout
Examples: soup, sand
Two or more phases (diff things you see)
Def: part of a sample that has
uniform composition and particles
Homogeneous mixture
Composition is uniform throughout
Examples: oil, kool-aid, glue, air, stainless steel
One phase
Also called solution (usually for liquids or gases)
Can be difficult to identify as homogeneous or heterogeneous - depends upon how closely you
look.
Generally, particle sizes of 1 nm or less in solution = homogeneous
Blood and milk are heterogeneous
C. Separating mixtures
Differences in physical properties can be used to separate mixtures
1. Decant
Separate oil and vinegar:
Pour off the oil = uses density of oil
Allow mixture to cool = oil freezes before vinegar
2. Filtration
Separate solid from liquid in a heterogeneous mixture
3. Distillation
Separate solid dissolved in a homogeneous mixture/solution
Liquid is boiled to produce vapor
Vapor is moved into another tube, where it is cooled and condensed to water
Solid is left in the flask
1. What type of properties can be used to separate mixtures?
2. Explain the term phase as it relates to homogeneous or heterogeneous mixtures.
3. Classify each of the following as a homogeneous or heterogeneous mixture.
a. food coloring
b. ice cubes in liquid water
c. mouthwash
d. mashed, unpeeled potatoes
4. How are a substance and a solution similar? How are they different?
5. In general, when would you use filtration to separate a mixture?
When would you use distillation to separate a mixture?
6. Describe a procedure that could be used to separate a mixture of sand and
table salt.
2.3 Elements and Compounds
A. Elements
Def: Simplest form of that has unique properties
Examples: oxygen, carbon, nitrogen
B. Compounds
Def: Substance that contains 2 or more elements combined in a fixed proportion (recipe)
Can be broken down into simpler substances by chemical means
Examples: water, H2O and sucrose C11H22O11
Breaking down compounds
Physical methods to separate mixtures can’t be used to break down compounds
boil water ---> liquid water, not hydrogen and oxygen
dissolve sugar cube in water -----> still have sugar, not C, H, and O
Must use chemical changes to break down a compound
Chemical change = change that produces matter with a
different composition than original matter
Examples: heating or electricity
Properties of compounds
Properties of compounds are different from individual elements
Example: Sodium chloride (NaCl) or table salt
White solid
Sodium alone is silver solid metal
Chlorine alone is yellowish gas
Example: H2O, water
Colorless liquid
Hydrogen oxygen both gases
C. Distinguishing between substances and mixtures
Hard to tell if substance or homogeneous mixture
If different varieties available, its probably a mixture
Milk: 2%, skim, whole
Gasoline: regular, premium, ultimate
Rule = If composition is fixed, the material is a substance.
If composition can vary, it is a mixture.
Chart page 50
Conceptual problem pg 51
D. Symbols and Formulas
Symbols represent elements
Capital letter or
Capital letter + lowercase letter
Carbon = C
Nitrogen = N
Chlorine = Cl
Sodium = Na
Formulas represent compounds
Use symbol for each element in compound
Number subscript to show how many atoms of each element are in
the “recipe”
Water H2O
2 atoms of hydrogen and 1 atom of oxygen
Glucose C6H12O6
6 atoms of Carbon, 12 atoms of hydrogen, and 6 atoms of Oxygen
Section Assessment 2.3
1. How is a compound different from an element?
2. How can you distinguish a substance from a mixture?
3. Name two methods that can be used to break down compounds into simpler substances.
4. Classify each of these samples of matter as an element, a compound, or a mixture.
a. table sugar
b. tap water
c. cough syrup
d. nitrogen
5. Write the chemical symbol for each element.
a. lead
c. silver
e. hydrogen
b. oxygen
d. sodium
f. aluminum
6. Name the chemical elements represented by the following symbols.
a. C
b. Ca
c. K
d. Au
e. Fe
f. Cu
7. What elements make up the pain reliever acetaminophen, chemical formula C8H9O2N?
Which element is present in the greatest proportion by number of particles?
8. Describe the relationship between the three items in each of the following groups. Identify
each item as an element, compound, or mixture.
a. hydrogen, oxygen, and water
b. nitrogen, oxygen, and air
c. sodium, chlorine, and table salt
d. carbon, water, and table sugar
Elements you need to know names and symbols for the test:
Elements by atomic number: 1-20, 26, 28, 29, 30, 47, 50, 79, 80, 82
1. _____ Hydrogen
2. _____Helium
3. _____Lithium
4. _____Beryllium
5. _____Boron
6. _____Carbon
7. _____Nitrogen
8. _____Oxygen
9. _____Fluorine
10. ____Neon
11. ____Sodium
12. ____Magnesium
13. ____Aluminum
14. ____Silicon
15. ____Phosphorus
16. ____Sulfur
17. ____Chlorine
18. ____Argon
19. ____Potassium
20. ____Calcium
26. ____Iron
28. ____Nickel
29. ____Copper
30. ____Zinc
47. ____Silver
50. ____Tin
79. ____Gold
80. ____Mercury
82. ____Lead
2.4 Chemical Reactions
A. Physical vs. Chemical Changes
Physical Changes (review from section 2.1)
Def: Some properties of a material change, but the composition does not change
Separating mixtures does not change their composition
Ex: Separate iron filings from sulfur using a magnet
Changing state of matter does not change the substance
Ex: H2O liquid changes to H2O vapor: it is still water
Physical changes can be:
Reversible: Freeze, melt, boil, condense
Irreversible: Cut, grind, crush
Chemical Changes
Def: composition of matter changes
Creates an entirely new type of matter
Also called chemical reaction
Substance present at start = reactant
Substances present at end = product
Reactant + Reactant
Example: Fe + O2
Product
FeO
B. Signs of Chemical Change
Transfer of energy
Heat is added - endothermic
Heat is released - exothermic
Change in color
Production of gas
Formation of precipitate
Def: solid forms and settle out from liquid mixture
Can only be certain of a chemical change if you test the composition
Some signs can occur even in physical changes
C. Conservation of mass
During any chemical reaction, the mass of reactants and products is always the SAME
No mass is gained or lost or destroyed in a reaction
You must consider the mass lost to any gas that is released
D. Chemical property
Describes ability of substance to undergo
chemical change
Examples:
Reactivity
Flammability
Ability to combust
Ability to ferment/turn sour
Ability to rust
Iron + Oxygen
Iron Oxide
Not chemical properties:
Ability to dissolve in water (solubility) = physical
ex: salt dissolves in water, but can reverse by evaporating water and get salt again
Changes of state: boiling or freezing = physical
Section Assessment 2.4
1. How does a chemical change affect the composition of matter?
2. Name four possible clues that a chemical change has taken place.
3. In a chemical reaction, how does the mass of the reactants compare with the mass of the
products?
4. What is the main difference between a physical change and a chemical change?
5. Classify the following as physical or chemical changes.
a. Water boils
b. Salt dissolves in water
c. Milk turns sour
d. a metal rusts
6. According to the law of conservation of mass, when is mass conserved?
7. Hydrogen and oxygen react chemically to form water. How much water would form if 4.8
grams of hydrogen reacted with 38.4 grams of oxygen?