chapter 2 - matter and change
DESCRIPTION
This presentation covers Chapter 2 on the general topic of Matter and Change. Substances or mixtures? Chemical or physical changes?TRANSCRIPT
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Chapter 2 – Matter & ChangeBy Kendon Smith – Columbia Central HS – Brooklyn, MI
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I. Properties of Matter
1. Matter is defined as anything that has mass and volume.
a. Mass: the amount of matter an object contains.
b. Volume: the amount of space an object occupies.
Chapter 2 – Matter and Change
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2. Describing Matter
a. Extensive Property: property that depends on the amount of matter in a sample
b. Intensive Property: property that depends on the type of matter in a sample
Examples: Identify the following properties of a sample as extensive or intensive.
Mass: ___ Color: ___ Flammability: ___
Volume: ___ Density: ___ Melting Point: ___
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3. Identifying Substances
a. Substance: matter that has uniform and definite composition.
- Uniform means it is the same throughout the sample.
- Definite composition means chemically the same all over the planet!
Examples: Water? Sand? Copper? Salt?
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b. Physical Property – a quality or condition of a substance that can be measured or observed without changing a substance’s composition.
Examples: color, solubility, odor, hardness, density,
melting point, boiling point, physical state, mass, volume
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4. States of Matter
A. Solids – form of matter with definite shape and definite volume
- Particles are packed tightly together
B. Liquids – form of matter with indefinite shape and definite volume
- Liquids take the shape of their container - Particles in liquids are almost incompressible - Particles in liquids usually expand slightly
when heated. - Particles in a liquid are close together, but
can flow past each other
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4. States of Matter
C. Gases – form of matter with indefinite shape and indefinite volume
- Particles in gases very far apart compared to liquids and solids.
- Particles in gases are easily compressed, pushing closer together.
* Vapors – Gaseous substances that are liquids or solids at room temperature.
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States of Matter
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5. Physical changes – alter a material without changing its chemical composition
- Physical changes can be classified as reversible or irreversible
a. Reversible changes: melt, freeze, boil, condense
b. Irreversible changes: break, split, grind,
cut, crush
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II. Mixtures
1. Mixture – a physical blend of two or more
substances.
a. Homogeneous mixture:
- completely uniform composition,
- parts are not readily distinguished
Examples – brine, gatorade, jello, creamy peanut butter
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II. Mixtures
1. Mixture – a physical blend of two or more
substances.
b. Heterogeneous mixture:
- not uniform composition
- parts are readily distinguished
Examples – sand and water, a salad, jello w/ fruit, chunky peanut butter
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2. Solution – a homogeneous mixture - may be solid, liquid, or gas
Examples – brine, sugar water, air, stainless steel
3. Phase – any part of a sample that with uniform composition and properties
How many phases?
Brine = ___ Oil/Vinegar = ___ Air = ___ Sand/Water = ___
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4. Separating Mixtures: Mixtures can be separated using physical means.
a. Decant, or pour off, a liquid layer.
Ex. Oil/Water Mix
b. Filtration: Separates solids from liquids with their
dissolved particles.
c. Distillation – Boil a liquid to become a vapor and condense it back.
d. Magnet – Pull out magnetic particles from a mixture.
e. Sorting - Physically separating by appearance
Ex. size, color, shape
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III. Elements and Compounds
1. Distinguishing elements and compounds
a. Elements – the simplest form of matter with a unique set of properties
- Elements are the basic building blocks of all other substances.
- Cannot be separated into simpler substances by chemical means.
Examples: hydrogen, oxygen, carbon
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III. Elements and Compounds
b. Compounds – two or more elements chemically combined in a fixed proportion
- Compounds can only be separated into simpler substances by chemical means,
but not by physical means, like mixtures.
Examples: water (H2O) sucrose (C12H22O11) carbon dioxide (CO2) sugar water???
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III. Elements and Compounds
c. Chemical change: produces matter with a different composition
- Bonds are broken to chemically separate elements.
- New bonds are formed to chemically join elements.
Example 1: sucrose (table sugar)
C12H22O11
HEAT12 C + 11 H2O
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III. Elements and Compounds
c. Chemical change: produces matter with a different composition
- Bonds are broken to chemically separate elements.
- New bonds are formed to chemically join elements.
Example 2: water (electrolysis)
2 H2OELECTRICITY
2 H2 + O2
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III. Elements and Compounds
2. Properties of Compounds
a. Properties of compounds can be quite different from those of their component elements.
- Each compound is a new, pure substance
with unique properties.
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a. Properties of compounds can be quite different from those of their component elements.
Example 1: Water – made of hydrogen and oxygen
Properties: Hydrogen:
Oxygen:
Water:
Extremely flammable gas
Gas that supports combustion
Non-flammable liquid!
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a. Properties of compounds can be quite different from those of their component elements.
Example 2: Table Salt – made of sodium and chlorine
Properties: Sodium:
Chlorine:
Sodium chloride:
Soft, silvery metal that reacts violently with water
Poisonous, yellowish gas
white, crystalline solid that we must eat!
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III. Elements and Compounds
3. Distinguishing Substances and Mixtures
a. Fixed composition – the material is a substance
b. Variable composition – the material is a mixture
KEY CONCEPT!
* Homogeneous mixtures look like substances because both appear to be made of one kind of matter.
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Matter
Substance(definite
composition)
Mixture(variable
composition)
Can be
physically separated
Element Compound
Can be chemically separated
Homogeneous(uniform; called
a solution)
Heterogeneous(not uniform;
distinct phases)
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Matter
Substance(definite
composition)
Mixture(variable
composition)
Element Compound Homogeneous(uniform; called
a solution)
Heterogeneous(not uniform;
distinct phases)
looks like
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4. Symbols and Formulas
a. Chemical symbol – one or two letters which represent each element
- First letter of the symbol is always capitalized, while the second letter is always lower case.
- Most symbols are derived from the Latin names for the elements.
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Name Latin Symbol
Sodium Natrium Na
Potassium Kalium K
Antimony Stibium Sb
Gold Aurum Au
Silver Argentum Ag
Iron Ferrum Fe
Lead Plumbum Pb
Mercury Hydrargyrum Hg
Tungsten Wolfran W
Copper Cuprum Cu
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b. Chemical formulas – use symbols to show the relative proportions of elements in a compound.
- Because compounds have fixed compositions, the chemical formula
for a compound is always the same.
- Subscripts are written next to the symbol and give us the proportion
of each element in the compound.
i. The number one is never written as a subscript,
it is assumed!
ii. If a subscript is written outside parenthesis, it multiplies the proportions of all the elements inside the parenthesis.
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Examples: What are the proportions of elements in each of the following compounds?
1. Table sugar (sucrose) = 12 carbons, 22 hydrogens, 11 oxygens
2. C2H5OH (ethanol) = 2 carbons, 6 hydrogens, 1 oxygen
3. Al(OH)3 = 1 aluminum, 3 oxygens, 3 hydrogens
4. (NH4)2CO3 = 2 nitrogens, 8 hydrogens, 1 carbon, 3 oxygens
5. Co3(PO4)2 = 3 cobalts, 2 phosphorus, 8 oxygen
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IV. Chemical Reactions
1. Chemical Changes: always involve a change in chemical composition
a. The ability of a substance to undergo chemical change is called a chemical property
b. Words that signify chemical change: burn, rot, rust, decompose, ferment, explode, corrode
c. Chemical properties can only be observed while a substance is undergoing a chemical change, during what is called a chemical reaction
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IV. Chemical Reactions
2. Chemical reaction – one or more substances change into new substances
a. Reactant – a substance present at the start of the reaction (BEFORE!)
b. Product – a substance produced during a reaction (AFTER!)
REACTANTS PRODUCTS
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3. Some basics rules for writing chemical reactions:
a. Reactants written on the left and products on the right with an arrow between.
b. Reactants are separated from each other with a + symbol. Same for products.
c. The arrows always points toward the products and can be read as “yields” or “produces” or “changes into”.
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Example 1 - Oxidation of Iron: The reaction between iron and oxygen yields
iron oxide.
Iron + Oxygen Iron oxide
Example 2: During combustion, ethanol reacts
with oxygen and produces carbon dioxide and water.
ethanol + oxygen carbon dioxide + water
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4. Recognizing Chemical Changes
a. Clues that a chemical reaction has taken place:
1. Energy is absorbed or released - hot or cold!
Examples: Burning wood – gives off heat Cook food – absorbs heat
*Note: There are energy changes during changes of state, which are only physical changes, so energy
change alone is not sufficient!
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a. Clues that a chemical reaction has taken place:
2. Change in color = new chemical has been formed!
3. Change in odor = smells are caused by chemicals!
4. Production of gas = you will see bubbles!
5. Production of a precipitate = a solid formed from liquid mixtures.
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5. Conservation of Mass
a. Law of Conservation of Mass: mass cannot be created or destroyed
b. In a chemical reaction, the mass of all the reactants must equal the mass of all the products.
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Examples:
10g of ice melt = 10g of water (phys. change)
2.5 kg of wood burn & produce 0.4 kg of ash?
- 2.1 kg of water vapor, carbon dioxide, and other gases released to air
1.5 grams of magnesium ribbon burns and the ashes weigh 2.1 grams
- combined with oxygen in the air to produce magnesium oxide
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