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Elements of Chemistry. The Central Science. Science is useful to our lives. It answers questions like… What is the ocean made of? How does gasoline serve as a fuel? How does your body use food to move?. Chemistry. Chemistry - the study of matter and the transformation it can undergo
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Elements of Chemistry The Central Science
Science is useful to our lives • It answers questions like… • What is the ocean made of? • How does gasoline serve as a fuel? • How does your body use food to move?
Chemistry • Chemistry - the study of matter and the transformation it can undergo • Matter is anything that occupies space • Therefore chemistry is very broad!
Chemistry as the Central Science • Chemistry touches all other sciences • Builds up from physics – the principles of physics are applied to the atom • Foundation for biology of living things • Foundation for Earth Sciences
Scientific Research • Activity aimed at discovering and interpreting new knowledge • Two types: • Basic • Applied
Basic Research • Leads to greater understanding of how the natural world operates • Foundation of knowledge leads to useful applications
Applied Research • Developing applications from our understanding of the natural world • Chemists focus on applied research • Medicine • Food • Water • Shelter
Past Century Advances have Impacted the Environment • We have harmed the environment by emptying waste into rivers, burying it underground and venting it into the air • Now involved in extensive efforts to clean it up! • For example: CFC’s
Chemists have learned how to produce aspirin using petroleum as a starting material. • Is this basic or applied research? • Applied
Atoms • Everything around us is made up of atoms • They are the smallest units of matter! • One grain of sand has 125 million trillion atoms!!!!
Molecules • Atoms link together to form larger, but still incredibly small units of matter called molecules • Example: Two hydrogen atoms and one oxygen atom link together to form one molecule of water • One cup of water has over 1,000,000,000,000,000,000,000,000 molecules of water!!! (that’s a trillion trillion!)
Levels of Magnification • Macroscopic • Can be seen, measured and handled • Microscopic • Seen only with a microscope • Used in biology
Submicroscopic • Realm of atoms and molecules • Focus of chemistry • Chemistry studies all levels of magnification, but emphasizes on the submicroscopic
Phases of Matter • Solid, liquid, and gaseous phases are distinguished by how the submicroscopic particles are held together
SolidS • In solids, the attraction is so strong that the particles are together in some fixed 3D arrangement • Atoms / molecules are still moving, but only with Brownian motion • Perpetual jiggling from collisions between particles
LiquidS (There is a mistake in your note here. Fix it to read as follows…) • Add heat to a solid until a certain temperature; increased vibrations disrupt the fixed arrangement • Gives rise to the liquid’s fluid mobility
Gases • Further heating of a liquid increases particle movement until the attractions are unable to hold them together • Molecules separate, forming gas • Gases occupy much more space (volume) than solids or liquids • They can be squeezed into smaller volumes using pressure (aerosol cans)
Physical Properties • The look or feel of a substance • Ex: Color, hardness, density, texture, phase • They can change when conditions change • If this happens, the substance’s composition does not change • Ex: When ice melts, it’s still H20
Physical Change • Change in the physical property, but not the chemical composition • Rip • Phase change
Is the melting of gold a physical change? • YES!!! Melting, the gold does not change the composition
Chemical Properties • Chemical properties describe how one substance reacts with others or how a substance transforms
New substance formed by the reaction of these chemicals with one another • CH4 + O2 > CO2 + 2H2O • Baking soda + vinegar > carbon dioxide + water • You eat food > build body tissue (you grow!)
These transformations involve a change in the way atoms and molecules are bonded to one another • Chemical bond - the attraction between two atoms that hold them together in a molecule
Example • Methane (CH4) = carbon with 4 hydrogen atoms attached • Oxygen (O2) = two oxygen atoms attached • When methane and oxygen react to produce carbon dioxide and water, they form new bonds with different partners • CH4 + 2 O2 CO2 + 2 H2O
What are Bonds? • Covalent Bonds • Share electrons in their outermost electron shell • Valence electrons • Bonds between nonmetals and other nonmetals • Ex: O2 and H2O
Ionic Bonds • Charged atoms / molecules attract (Ions) • Opposites attract • Loose or gain a valence electron in the outermost electron shell • Metal + Nonmetal • Ex: NaCl, KBr, CaCl2
Chemical Change • Any change in a substance that involves a rearrangement of the way its atoms are bonded • Beginning materials are said to be reactants • They will react with each other to form new compounds
Example • Copper reacts with silver nitrate to produce copper nitrate and silver • Methane reacts with oxygen to produce carbon dioxide and water
Chemical Change = Chemical Reaction • Chemical reaction – new materials are formed by a change in the way atoms are bonded together
Physical Change vs. Chemical Change SIMILARITIES: • Change in physical appearance and energy • Water looks different than ice • Physical change • Rust looks different than metal • Chemical change
Physical Change vs. Chemical Change • SAME material, only new conditions • Typically less energy • Restore original conditions restores original appearance • No new chemical identity • Formation of a NEW material • Unique set of physical properties • Cannot restore original appearance without another chemical change Physical Change Chemical Change
Example • Growth of 1 inch in a year. • Chemical or physical change? • CHEMICAL!!! Body is changing food into body tissue
Elements • An element is made of only one type of atom! • Element is used in reference to an entire macroscopic or microscopic sample • Atom is used in reference to the submicroscopic particles in a sample • Elements are made of atoms; NOT vise versa
Elemental Formula • Tells how many atoms are bound together in an element • Elements with basic units are individual atoms = Write the chemical symbol • For example: Au, Cu, Pb, K
Elemental Formula (continued) • Elements in which basic units are two or more atoms bonded together = Chemical symbol + subscript • For example: All the –gens (oxygen O2, hydrogen H2 and nitrogen N2) • and all the –ines (fluorine F2, chlorine Cl2, bromine Br2, iodine I2, astatine At2) • and Sulfur S8
Why is gold’s symbol not G? • Named a long time ago and given a Latin name (Aurum, Au) • Why is lead’s symbol not L? • Named a long time ago and given the Latin name plumbum (Pb)
Oxygen we breathe (O2) is converted to ozone (O3) in the presence of an electric spark. • Is this a physical or chemical change? • Chemical
21. 5Elements Combine to form Compounds • Atoms from different elements bond to one another to form compounds • NaCl – table salt • NH3 – ammonia • CO2 – carbon dioxide • CO – carbon monoxide • H2O - water
Chemical Formula • Write symbols for the number of each element in the compound • Elements closer to the left side of the periodic table are written first • If there is only one atom, no subscript is needed • The number 1 is always understood
Examples • Sodium chloride = NaCl • One sodium for every chlorine • Calcium chloride = CaCl2 • One calcium for every two chlorines • Aluminum chloride = AlCl3 • One aluminum for every three chlorines
Compound vs. Elemental Properties • Compounds have physical and chemical properties that are different than their elemental properties • Sulfur vs. Sulfur dioxide
Example • Sodium chloride (table salt) is different than elemental sodium and chlorine • Sodium – soft metal, reacts violently with water • Chlorine – yellow-green gas, toxic • NaCl – translucent, brittle, colorless crystal, non-toxic essential to human life
H2S is one of the smelliest compounds –the smell of ROTTEN EGGS is due to the hydrogen sulfide they release. • Do think elemental sulfur, S8, is just as smelly? • NO!!! Compounds are different than elements they are made from
Chemical Formula • Remember -- Different elements combine to make new compounds with different properties • And if the same elements combine in different ratios – THIS MAKES DIFFERENT COMPOUNDS!!! • For Example: O2 –oxygen; needed by animals to breathe • O3 –ozone; which is poisonous to breathe
21.6 Chemical Reactions are represented by chemical equations • In chemical reactions, atoms rearrange to create one or more new compounds • This can be summed up in a written chemical equation
21.6 Chemical Equations • Reacting substances (reactants) are to the left of the arrow • Newly formed substances (products) are to the right of the arrow • REACTANTS PRODUCTS
Chemical Equations • Reactants and Products are represented by their elemental or chemical formulas • Phases are shown with subscripts: • (s) for solid, (l) for liquid, (g) for gas • H2O(s), H2O(l), H2O(g) • Compounds dissolved in water are known as aqueous • NaCl(aq)
Coefficients • Numbers placed in front of the reactants or products to show the ratio of combination or formation • Represent number of individual atoms or molecules • If NO coefficient, it is understood to be 1 • CH4 + 2O2 > CO2 + 2H2O