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Chemistry

Discover the composition, structure, and properties of matter, as well as the changes and energy associated with these changes. Learn about the two classes of matter, homogeneous and heterogeneous, as well as the building blocks of matter, elements, and compounds. Understand the difference between molecules and compounds, and explore mixtures and solutions. Dive into the properties of substances and the different types of changes matter can undergo. Finally, uncover the laws of conservation of matter and energy.

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Chemistry

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  1. Chemistry The study of the composition, structure and properties of MATTER, the changes which matter undergoes and the energy that accompanies these changes.

  2. What is matter? • Matter is anything that occupies volume and has mass • Volume • measure of space that an object occupies • Mass • measures the quantity of matter (how much?) • not affected by gravity

  3. 2 classes of matter • Homogeneous • Samples are identical throughout • Pure substance • ex. elements, compounds • Heterogeneous • Samples are not identical throughout • NOT a pure substance • ex. mixturesexcept solutions

  4. Homogeneous Heterogeneous Particle Diagrams

  5. ELEMENT Building blocks of matter • Contains only one kind of atom • Can’t be broken down into simpler substances by ordinary chemical means • Elements are represented with symbols

  6. / one atom He Ne Ar Kr Xe Rn MONOATOMIC Elements • An element in the free state found ONLY by itself • monoatomic molecules • Group 18 elements • Inert gases

  7. / two atom DIATOMIC Element • The simplest form of these elements is a pair of atoms • There are 7 diatomic elements Go to 7 and make a 7. Don’t forget Hydrogen!

  8. Molecules 2 different non-metals bonded 2 same non-metals bonded Molecule vs. Compound • Both made of particles called atoms Compound Formed when 2 or more atoms from different elements bond chemically ex. metal & non-metal

  9. Important Characteristics of a Compound • Individual atoms lose their original properties • Compounds can be decomposed by chemical changes • Composition is fixed

  10. MIXTURE • Physical combination of 2 or more substances • Composition varies • NO BOND between substances that are physically combined • SiO2 & NaCl • Air (O2, N2, CO2 . . . ) • salt water solution

  11. NaCl(s) + H2O(l) NaCl(aq) SOLUTION • Type of homogeneous mixture • But not a substance solute solvent aqueous solution Air (mixture of gases) considered a homogeneous mixture The particles are in constant motion and evenly distributed.

  12. . . . Of a compound Chemical means Decomposition reaction w/ heat . . . Of a mixture Physical means If (s) & (l) Filtration If dissolved solid & liquid (aq) Evaporation or distillation If same phase (l) Boiling points (s) melting points Separating Contents

  13. Compound Compositions • The elements making up a compound are in a definite proportion / ratio • Using math • determine % composition • determine the mass of elements in a compound

  14. What is the % by mass H2O ? a.k.a. Percent composition • % = part/whole x 100 • Part? • Is what you’re looking for • Whole? • Is where the part came from

  15. Step 1 • Determine gram formula mass of compound. • ADD IT ALL UP!!!! • Step 2 • Plug into formula

  16. More complicated . . . A 13.60g sample of a compound containing only magnesium and oxygen is decomposed. 5.40g of oxygen is obtained. What is the % comp of magnesium in the compound?

  17. Even more complicated • In 115g of CO what mass is carbon and how many g are oxygen? Play the units game!

  18. Properties Set of characteristics by which a substance is recognized Properties Set of characteristics by which a substance is recognized • Physical Properties • can be determined without changing the chemical composition of a substance • Physical changes • DO NOT result in new substances.

  19. Intensive properties that DON’T depend on sample size density D = m/v melting point boiling point useful in identifying substances Extensive properties that DO depend on sample size volume weight mass Physical properties are intensive or extensive

  20. Chemical Properties determined during a chemical reaction with another substance Chemical Changes Results in the rearrangement of atoms  a new substance Color change Gas or precipitate produced Heat produced Heat absorbed BUT! Chemical Properties

  21. Matter can undergo physical and chemical changes, but matter cannot be created or destroyed. Energy can change form, but energy cannot be created or destroyed Law of Conservation of Matter Law of Conservation of Energy

  22. The End

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