# Chapter 2 Matter & Change.

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Chapter 2 Matter & Change

Describing Matter Matter Anything that takes up space and has mass
A pure substance or as a matter of substances Properties used to describe matter can be classified as extensive or intensive Extensive Property Depends on the amount of matter in a sample Intensive Property Depends on the type of matter in a sample (i.e. hardness)

Extensive Property Mass
A measure of the amount of matter the object contains Volume A measure of the space occupied by the object

States of Matter Three states of matter are: solid, liquid, and gas.

Solid Matter that has definite shape and volume
Particles are tightly packed together (not easily compressed)

Liquid Matter that flows, has a fixed volume, and takes the shape of its container Particles are packed less tightly than in a solid (not easily compressed)

Gas (Vapor) matter that has no definite shape or volume
It takes the shape of its container and can be compressed Particles in a gas are spaced far apart (easily compressed)

Sample Exercise What is the physical state of each of the following at room temperature? Gold Gasoline Helium

Physical Changes The shape of a sample changes, but the composition stays the same Boil, freeze, melt, condense, break, split, grind, cut, and crush. Physical changes can be reversible or irreversible

Section Assessment In what way are liquids and gases alike?
In what way are liquids and solids different? Is the freezing of mercury (Hg) a reversible or irreversible physical change?

Classifying Mixtures Consists of a physical blend of two or more substances Can be classified as heterogeneous mixtures or as homogenous mixtures

Heterogeneous mixture
not uniform in composition Ex: salad, stew

2. Homogeneous mixture A complete uniform composition
Ex: iced tea, lemonade Also called a solution

Differences in physical properties can be used to separate mixtures
Distillation A liquid is boiled to produce a vapor that is then condensed into a liquid This process separates liquids by their boiling points (and impurities) Separating Mixtures

Filtration Separates a solid from the liquid in a heterogeneous mixture

Distillation A liquid is boiled to produce a vapor that is then condensed into a liquid This process separates liquids by their boiling points (and impurities)

Fermentation Plums Mashed Plums

Distiller

Plum Mash Poured into Distiller
Top View

Distiller Set Ablaze

Moonshine

3. Chromatography – a technique that is used to physically separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material

Classify each of the following as a homogenous or heterogeneous mixture
Food coloring Ice cubes in liquid water Mouthwash Mashed, unpeeled potatoes Section Assessment

Section assessment When would you use filtration to separate a mixture? When would you use distillation to separate a mixture?

Elements Simplest forms of matter Cannot be broken down
Building blocks for all other substances Ex: Periodic Table of Elements

Sodium (Na) Natrium

Chlorine (Cl)

Compounds Contains two or more different elements chemically combined in a fixed proportion Can be broken down into elements, by a chemical change Ex: water, sodium chloride

Sodium Chloride (Table Salt)

Figure: 01-05a-d

Figure: 01-01

Distinguishing Substances and Mixtures
Beryl - Be3Al2(SiO3)6 Substance – if the composition of the material is fixed (elements, and compounds) Distinguishing Substances and Mixtures

Mixture If the composition of a material may vary Various Granite

Practice Problems Liquid A and Liquid B are clear liquids. They are placed in open containers and allowed to evaporate. When evaporation is complete, there is a white solid in container B, but no solid in container A. From these results, what can you infer about the two liquids?

Practice Problems A clear liquid in an open container is allowed to evaporate. After three days, a solid is left in the container. Was the clear liquid an element, a compound, or a mixture? How do you know?

Symbols and Formulas Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds.

Chemical Symbol Each element is represented by a one or two letters
The first letter is always capitalized When a second letter is used, it is lowercase Chemical formulas are used to represent compounds: CO2

Section Assessment Write the chemical symbol for each element Lead
Oxygen Silver Sodium Hydrogen Aluminum

Section assessment Name the chemical elements represented by the following symbols C Ca K Au Fe Cu

Chemical Change Change that produces matter with a different composition than the original matter Usually involves burning, rotting, decomposing, fermenting, exploding, rusting, corroding. Ex: milk spoils, electrolysis of water

Figure: 01-10

Chemical Reactions Chemical Property
The ability of a substance to undergo a specific chemical change During a chemical change, the composition of matter always changes A substance that is present at the start of the reaction is a reactant A substance produced in the reaction is a product

Recognizing Chemical Changes
Possible clues to a chemical change include: A transfer of energy A change in color The production of a gas The formation of a precipitate Precipitate (ppt) A solid that forms and settles out of a liquid mixture, and is usually indicated by a color change

A transfer of energy

A change in color (precipitate)

The production of a gas

Conservation of Mass During any chemical reaction, the mass of the products is always equal to the mass of the reactants Mass is conserved Mass is neither created nor destroyed

Section Assessment Classify the following changes as physical or chemical changes Water boils Salt dissolves in water Milk turns sour A metal rusts

Section Assessment 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? 2H2 + O2  2H2O

Section Assessment When ammonium nitrate (NH4NO3) explodes, the products are nitrogen, oxygen, and water. When 40 grams if ammonia nitrate explode 14 grams of nitrogen and 8 grams of oxygen form. How many grams of water form? NH4NO3  N2 + O2 + H2O

Key Concepts - Properties of Matter
Properties used to describe matter can be classified as extensive or intensive Every sample of a given substance has identical intensive properties because every sample has the same composition Three states of matter are solid, liquid, and gas Physical changes can be classified as reversible or irreversible

Key Concepts - Mixtures
Mixtures can be classified as heterogeneous mixtures or as homogeneous mixtures, based on the distribution of their components Difference in physical properties can be used to separate mixtures

Key Concepts – Elements and Compounds
Compounds can be broken down into simpler substances by chemical means, but elements cannot If the composition of a material is fixed, the material is a substance. If the composition may vary, the material is a mixture Chemists use chemical symbols to represent elements, and chemical formulas to represent compounds Key Concepts – Elements and Compounds

Key Concepts – Chemical Reactions
During a chemical change, the composition of matter always changes Four possible clues to chemical change include a transfer of energy, a change in color, the production of a gas, or the formation of a precipitate During any chemical reaction, the mass of the products is always equal to the mass of the reactants