Chapter 1/2 Notes

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Chapter 1: Intro to Chemistry

Chemistry

Is the study of the composition of matter and the changes that matter undergoes

What is matter?

Matter is anything that has mass and takes up space

Affects all aspects of life and most natural events because living and non-living things are made up of matter

Areas of Study

Organic Chemistry

Study of all chemicals containing carbon

Inorganic Chemistry

Study of all chemicals that in general don't contain carbon

Found mainly in non-living things

Biochemistry

Study of processes that take place in organisms

Muscle contraction and digestion

Analytical Chemistry

Focuses on the composition of matter

Measuring the level of lead in drinking water

Measuring the level of carbon dioxide in the atmosphere

Physical Chemistry

Mechanism, rate & energy transfer that occurs when matter undergoes a change

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Why Study Chemistry?

Useful in explaining the natural world

Can explain why water expands when it freezes

Explain why the texture of eggs changes from runny to firm as eggs are boiled

Preparing people for career opportunities

Reporter

Turf Manager (soil chemistry)

Firefighter

Scientific Method

A systematic approach to the solution of a scientific problem

Steps include making observations, proposing and testing hypotheses, and developing theories

Scientific Thinking

Observation

This can lead to a question

Hypothesis

A proposed scientific explanation for set of observations

Tested by controlled experiments or by gathering more data

Experiments

A procedure used to test a hypothesis

Independent Variable (manipulated variable) --- variable that is changed

Dependent Variable (responding variable) ---- variable that is observed during the experiment

Data

Use data to make inferences

Logical interpretation based on prior knowledge/experience

Quantitive

Expressed as numbers -- quantity

Qualitative

Descriptive & involves characteristics -- quality

A hypothesis is useful only if it accounts for what is actually observed

When experimental data does not fit, the hypothesis must be changed

For results to be accepted experiment must produce the same result no matter how many times it is repeated

Once a hypothesis meets the test of repeated experimentation it may become a theory (a well-tested explanation for a set of observations)

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Chapter 2: The Study of Matter

What is Matter?

Anything that has mass and takes up space

Mass

Amount of material in an object

Volume

Amount of space the object occupies

To fully understand matter one must observe matter's physical properties

Basic Building Blocks of Matter

Fundamental building blocks of matter are atoms and molecules

These particles make up elements & compounds

Atom

Smallest unit of an element that maintains the chemical identity of that element

Element

Pure Substance that cannot be broken down into simpler, stable substances is made of one type of atom

Compound

Substance that can be broken down into simple stable substances

Made from atoms of 2 or more elements that are chemically bonded

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Physical Properties

Characteristics of a substance that can be observed without changing (altering) the identity of the substance

Extensive(EA) - depends on the amount of matter in a sample

Examples: mass, volume, and the amount of energy in a substance

Intensive(IT) - depends on the type of matter in a sample, not the amount of matter

Examples: hardness, density, melting/boiling point, absorbency, ability to conduct electricity, and to transfer energy as heat

States of Matter

Depending on the situation a substance can exist in 3 different physical states

Soli, Liquid, Gas **

Solid

Holds a particular shape and has a definite volume

Doesn't depend on shape of the container

Tightly packed together

Orderly arrangement

Almost incompressible (difficult to squeeze)

Expand slightly when heated

Liquid

Doesn't hold its own shape, but does occupy a definite volume

Flows freely with the container

Close contact, not rigid/orderly

Volume doesn't change -- volume is fixed with the shape of the container

Expands slightly when heated

Almost incompressible

Gas

Has no definite shape/volume

Expands to fill the available volume of its container

Particles are far apart

Can be compressed

The difference between a gas and a vapor:

Gas: exist in a gas state at room temperature (oxygen)

Vapor: gas state of a substance that is generally a solid or liquid at room temperature

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Physical Changes

Alter in form, but the matter itself doesn't change

Some properties can change but the composition doesn't change

Examples: boil, freeze, melt, condense, crush, tear, grind, break, etc

Can be reversible or irreversible

Cutting & filing are examples of irreversible

Changes in state are reversible

Physical Change of a substance from one state to another

Chemical Properties

The ability of a substance to undergo a specific chemical change

Characteristics of a substance that can't be observed without altering the substance

Examples: Flammability, reactivity, and stability

Can only be observed if a chemical change is taking place

Chemical Reactions/Chemical Changes

One or more substances change into one or more new substances (alters the identity)

Reactants and Products

Reactants ---- substances that react

Products ----- substances that are formed

Examples: burning wood, cooking food, and rusting of iron

Recognizing a Chemical Change

Color Change

Heat is emitted/absorbed

Light is emitted

Gas is emitted

Precipitate forms --- producing a solid

If the substance's identity is not altered then a physical change has taken place

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Law of Conservation of Mass

During any chemical reaction, the mass of the products is always equal to the mass of the reactants

Whether a physical change or chemical reaction has taken place, mass is always conversed

Mass is neither created/destroyed, it is just converted

Classifying Matter

To classify matter, one must determine whether the matter has a definite composition or a variable composition

If the material is uniform/has a definite composition, (homogeneous) then it is called a pure substance

Pure Substance: has a fixed composition and differs from a mixture in the following ways:

Every sample of a given pure substance has the exact same characteristic properties

Every sample has exactly the same composition

A pure substance can be classified as an element or compounds

Elements

The simplest form of matter that cannot be broken down into simpler substances by a chemical change

(Elements cannot be broken down by chemical means, but compounds can)

Compounds

2 or more elements chemically combined in a fixed proportion(CO2, H20, etc.)

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Symbols & Formulas

Symbols used to represent elements

Chemical symbols: Au, Ag, H, N, etc.

Formulas represent compounds (H20)

Chemical formulas: NaCl, CuSO4, AgCl

Subscripts

Indicate relative proportions of elements in a compound

Since compounds have a fixed composition, the formula for a compound is always the same

Classifying Matter

If the material has a variable composition, then it is called a mixture

Combination of 2/more pure substances each of which retains its own composition & properties

Two types of mixtures: Heterogeneous & Homogeneous

Examples: vegetable soup & air

Can be physically separated into pure substances (salt water)

Homogeneous Mixtures

The mixture is uniform throughout

Made up of one phase

Can be called solutions (homogeneous)

Mostly liquids

Examples: air, sugar, salt, stainless steel, & seawater

Heterogeneous Mixtures

The mixture is not uniform throughout

Made up of different phases

Examples: veggie soup, milk, Italian dressing

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Separating a Heterogenous Mixture

Decantation (strainer)

Let settle, and pour out the liquid

Easy, but not complete

Gravity Filtration

Save liquid

Vacuum Filtration

Save solid

Centrifuge (Gravitron @ fair)

Easy and fast, but hard to remove solid

Separating Homogeneous Mixtures

Distillation

Use 2 different boiling points to separate 2 or more liquids

Chromatography

Send through a medium (dense)

Smaller molecules will travel faster

Different substances move at different rates

Crystallization

Solid dissolved in a liquid

Allow the liquid to partially evaporate

Solid crystals will fall out