Chemistry is the study of matter and the changes it undergoes. Matter, does it matter? Yes…it does! Chemistry is the study of matter and the changes it undergoes.

Matter We define matter by using two criteria. Something is considered to be matter if it: Has mass Takes up space What are some examples?

Matter

Not Matter Energy Light Ideas Happiness Love

Classifying matter - Why? To organize what we have When things are organized – we know what we have And more importantly, we know what we do NOT have.

Classifying matter Matter Does it have a fixed formula? Yes No Substance Mixture *Having a fixed formula *No fixed formula *Cannot be separated by *Can be separated physical means by physical means

Can it be separated chemically? Classifying matter Substances Can it be separated chemically? No Yes Element Compound *Simplest form of matter *Two or more elements *Cannot be broken down further * Can be broken down *Found on the periodic table H2O -> H2 + O2

Substances: element or compound Elements- simplest kind of matter cannot be broken down any simpler and still have properties of that element! all one kind of atom. Compounds are substances that can be broken down only by chemical methods when broken down, the pieces have completely different properties than the original compound. made of two or more atoms, chemically combined (not just a physical blend!)

Symbols & Formulas Currently, there are 117 elements -Only 92 of the 115 presently known elements occur naturally. Elements have a 1 or two letter symbol, and compounds have a formula. An element’s first letter always capitalized; if there is a second letter, it is written lowercase: B, Ba, C, Ca, H, He

Some elements pair up and only exist as diatomic molecules Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, and Bromine are always found as diatomic molecules: How do I remember this? H N F O I Cl Br HONClFIBr (say HONKLE-fibber) BrINClHOF (say Brinckle-hoff) I Have No Bright Or Clever Friends ClIF H Bron HOFBrINCl Twins (twins because they exist in pairs) There are seven such elements. The first one is the first element Hydrogen; the rest form a 7 on the periodic table: N, O, F across, then going down Cl, Br, I.

Elements vs. Compounds Compounds can be broken down into simpler substances by chemical means, but elements cannot. A “chemical change” is a change that produces matter with a different composition than the original matter.

What does this drawing represent? Is this a compound, element, or both?

What does this drawing represent? Is this compound, or element? Answer: Element

What does this drawing represent? Is this a compound, element, or both?

What does this drawing represent? Is this a compound, or element? Answer: compound

What does this drawing represent? Is this a compound, element or both?

What does this drawing represent? Is this a compound, or element or mixture of both? Answer: both compounds and elements

Identify each of the containers as containing either elements, compounds, or both Unnumbered Figure, pg. 9 Investigating Chemistry, 2nd Edition © 2009 W.H. Freeman & Company

Identify each of the containers as containing either elements, compounds, or both Unnumbered Figure, pg. 9 Investigating Chemistry, 2nd Edition © 2009 W.H. Freeman & Company Answers: Elements: b Compounds: a, d, e Both compounds and elements: c

Classifying matter Mixtures Is every sample taken the same? No Yes Heterogeneous Homogenous *Every sample is different *Every sample is the same *Usually easy to separate * Called “Solution” Solute Solvent What gets dissolved Usually water

Mixtures Have variable composition. Homogeneous Mixture Having visibly indistinguishable parts; solution. Heterogeneous Mixture Having visibly distinguishable parts. Copyright © Cengage Learning. All rights reserved

Homogeneous Mixtures Copyright © Cengage Learning. All rights reserved

Homogeneous vs. Heterogeneous Mixtures Copyright © Cengage Learning. All rights reserved

Classification of Matter

Describing Matter Properties used to describe matter can be classified as: Extensive – depends on the amount of matter in the sample - Mass, volume, calories are examples Intensive – depends on the type of matter, not the amount present - Hardness, Density, Boiling Point

Properties are… Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the material’s composition. Examples- color, hardness, m.p., b.p. Chemical Properties- a property that can only be observed by changing the composition of the material. Examples- ability to burn, decompose, ferment, react with, etc.

Some Examples of Physical and Chemical Properties Physical Properties Chemical Properties Temperature Amount Color Odor Melting point Solubility Electrical conductivity Hardness Rusting (of iron) Combustion (of coal) Tarnishing (of silver) Hardening (of cement)

Properties of Compounds Quite different properties than their component elements. Due to a CHEMICAL CHANGE, the resulting compound has new and different properties: Table sugar – carbon, hydrogen, oxygen Sodium chloride – sodium, chlorine Water – hydrogen, oxygen

States Of Matter Solids: .

States Of Matter Liquids: Indefinite shape, definite volume Take the shape of container Particles are close together, but mobile Particles move slowly

States Of Matter Indefinite shape Indefinite volume Gases: Indefinite shape Indefinite volume Take the shape and volume of container Particles are far apart Particles move fast

States Of Matter Plasma: Energized gases Do not have a fixed volume. They are mostly empty space and can be compressed. Do not have a fixed shape. They tend to fill the entire container.

States Of Matter How do we change states of matter? It requires energy. What does the energy do? It makes the molecules move. This causes friction, which results in heat being generated

4th state: Plasma - formed at high temperatures; ionized phase of matter as found in the sun

Condense Freeze Melt Evaporate Solid Liquid Gas

Learning Check S1 Match: (1) solid, (2) liquid, or (3) gas. ____ A. Has a definite volume, but shape of the container. ____ B. Its particles are moving rapidly. ____ C. Fills the volume of a container. ____ D. Particles are in a fixed structure. ____ E. Particles are close together, but mobile.

Solution S1 Match: (1) solid, (2) liquid, or (3) gas. _2_ A. Has a definite volume, but shape of the container. _3_ B. Its particles are moving rapidly. _3_ C. Fills the volume of a container. _1_ D. Particles are in a fixed structure. _2_ E. Particles are close together, but mobile.

Physical vs Chemical Properties Properties are - Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the material’s composition. Examples- color, hardness, m.p., b.p. Chemical Properties- a property that can only be observed by changing the composition of the material. Examples- ability to burn, decompose, ferment, react with, etc.

Physical vs. Chemical Change Physical change will change the visible appearance, without changing the composition of the material. Boil, melt, cut, bend, split, crack Is boiled water still water? Can be reversible, or irreversible Chemical change - a change where a new form of matter is formed. Rust, burn, decompose, ferment

Physical and Chemical Changes How to tell the difference

Physical Change Change in the form of a substance, not in its chemical composition. Example: boiling or freezing water Can be used to separate a mixture into pure compounds, but it will not break compounds into elements. Distillation Filtration Chromatography Copyright © Cengage Learning. All rights reserved

Physical Change Substance may seem different, but the way the atoms link up is the same.

It’s a physical change if It changes shape or size It dissolves It changes phase (freezes, boils, evaporates, condenses)

Chemical Change Changes the way the molecules link up Makes new substances

It’s a chemical change if…. It burns Temperature changes without heating/cooling

It’s a chemical change if... It bubbles (makes a gas)

It’s a chemical change if... It changes color It forms a precipitate

What kind of change is it if someone... Tears up paper? Physical change Mixes salt and water?

What kind of change is it if someone... Burns paper? Chemical change Evaporates salt water? Physical change

What kind of change is it if someone... Mixes vinegar and baking soda? Chemical change

Heat and light are often evidence of a chemical change. A change in which one or more substances are converted into different substances. Heat and light are often evidence of a chemical change.

Chemical Changes The ability of a substance to undergo a specific chemical change is called a chemical property. iron plus oxygen forms rust, so the ability to rust is a chemical property of iron During a chemical change (also called chemical reaction), the composition of matter always changes.

Recognizing Chemical Changes Energy is absorbed or released (temperature changes hotter or colder) Color changes Gas production (bubbling, fizzing, or odor change; smoke) formation of a precipitate - a solid that separates from solution (won’t dissolve) Irreversibility - not easily reversed But, there are examples of these that are not chemical – boiling water bubbles, etc.

Law of conservation of mass During any chemical reaction, the mass of the products is always equal to the mass of the reactants. All the mass can be accounted for: Burning of wood results in products that appear to have less mass as ashes; where is the rest? Law of conservation of mass