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Unit 2: Matter And Energy

Unit 2: Matter And Energy. Chemistry. In this science we study matter and the changes it undergoes. Matter is defined as anything that has mass and takes up space. The Nature of Matter. Chemists are interested in the nature of matter and how this is related to its atoms and molecules.

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Unit 2: Matter And Energy

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  1. Unit 2: Matter And Energy

  2. Chemistry In this science we study matter and the changes it undergoes. Matter is defined as anything that has mass and takes up space.

  3. The Nature of Matter Chemists are interested in the nature of matter and how this is related to its atoms and molecules. Gold Mercury

  4. Chemistry & Matter • We can explore the MACROSCOPIC world — what we can see — • to understand the MICROSCOPIC or SUBATOMIC worlds we cannot see. • We write SYMBOLS to describe these worlds.

  5. A Chemist’s View of Water Macroscopic H2O (gas, liquid, solid) Symbolic Microscopic

  6. Kinetic Molecular Theory

  7. Kinetic Nature of Matter Matter consists of atoms and molecules. What differences do you see between the different states?

  8. STATES OF MATTER • _______ — have rigid, fixed shape and volume. External shape can reflect the atomic and molecular arrangement. • Little space between atoms, little energy • Most dense state (one exception) • _______ — have no definite shape but have definite volume • Some space between molecules, medium energy • Have a medium density • _______ — expand to fill their container. • Indefinite shape and indefinite volume • A lot of space between molecules, High energy • Have very low density

  9. OTHER STATES OF MATTER • PLASMA— an electrically charged gas; Example: the sun or any other star • Aqueous — a substance dissolved in water. Example: an aqueous salt is a salt dissolved in water

  10. Phase Changes *Know the names of the phase changes

  11. Phase Change Diagram Normal boiling point Normal melting point --------------------------------------------------------------- 1 atm A Phase Change Diagram is the representation of phase transformation and also the different phases and conditions of transformation of a matter. *(Normal means at 1atm or at sea level)

  12. Phase Change Diagram of Water *Water is one of few substances who’s solid state is less dense than its liquid state. *Most substances solid phase is more dense than its liquid phase

  13. Phase Change Diagram What state of matter does point G represent? What do we call point B? What do we call moving from point G to point A? What substance could this heating curve represent?

  14. Phase Change Graph How do we measure kinetic energy? Where is kinetic energy increasing? Where is potential energy increasing?

  15. Phase Change Diagram Which letter represents the liquid phase? What is the melting point of this substance? Which letter represents sublimation? Which letter has the lowest energy? E D C B A

  16. Density • Density is mass per unit volume • D= m/V • Density is measured in units of g/cm3 or g/mL • Density is a physical property • The density of water is 1 g/mL • How would you determine the density of a metal experimentally?

  17. D=m/V • What is the density of an object that weighs 4.0g and has a volume of 1.00 mL? • What is the mass of an object with a density of 0.990 g/mL and a volume of 12mL? • What is the volume of an object with a density of 1.23 g/mL and a mass of 50.00g?

  18. Types of Properties • Intensive Properties… • Are independent of the amount of the substance that is present. • Density, boiling point, color, etc. • Extensive Properties… • Depend upon the amount of the substance present. • Mass, volume, energy, etc.

  19. Types of Properties • Physical Properties… • Can be observed without changing a substance into another substance. • Chemical Properties… • Can only be observed when a substance is changed into another substance/ when a chemical reaction occurs.

  20. Physical Properties What are some physical properties? • Color • Melting and boiling point • Odor • Shape • Density • Phase of matter

  21. Chemical Properties • Examples of Chemical Properties: • Heat of combustion • Flammability • Toxicity • Reactivity • Rusting

  22. Physical Changes • can be observed without changing the identity of the substance Some physical changes would be • Crushing • Cutting • Boiling of a liquid • Melting of a solid • Dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION. • Phase changes are always physical

  23. Chemical Properties and Chemical Change • Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules. • Examples: • Burning hydrogen (H2) in oxygen (O2) gives H2O. • Iron rusting to make iron oxide

  24. Sure Indicators of a Chemical Change • Heat • Light • Effervescence- bubbling/ Gas Produced (not from boiling!) • Odor produced • Precipitate – a solid formed by mixing two liquids together • Looks like a solid or looks cloudy • Some times color

  25. Physical vs. ChemicalProperties • physical • chemical • physical • physical • chemical • Examples: • melting point • flammable • density • magnetic • tarnishes in air

  26. Physical vs. ChemicalChanges • Examples: • rusting iron • dissolving in water • burning a log • melting ice • grinding spices

  27. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Matter Flowchart MATTER yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

  28. Elements and Compounds • Atoms are the building blocks of matter. • Each element is made of the same kind of atom. • Represented by elemental symbol • Example: Au or O • A compound is made of two or more different kinds of elements that are chemically bonded. • Represented by a chemical formula (example H2O) • Always in definite proportions • A pure substance refers to an element or a compound

  29. Types of Mixtures • Mixtures- Combination of 2 or more pure substances physically combined. • Alloy- a mixture of metals Homogeneous Mixture – Same throughout (AKA solution) Heterogeneous Mixtures– Not the same throughout(Can be visibly seen)

  30. Examples • Label the following as an element, compound, solution, alloy, or heterogeneous mixture • Lemonade • Sodium Chloride • Gold • Steel • Pizza • Sulfur • Oil and water

  31. Practice • Label the following pictures as an element, compound, or mixture; • Each shape is a different element • Shapes touching represents a chemical bond

  32. Physical and Chemical Separation • Physical separation is separation without chemically changing the composition of a substance • Only mixtures and solutions can be physically separated • Example: separating a solution of salt water by boiling off the water • The salt and water are not chemically changed they are just physically separated from each other • Chemical separation is the separation of a compound by chemically changing the composition of a substance • Involves breaking of chemical bonds • Only compounds can be chemically separated • Example: separating a water molecule into hydrogen and oxygen molecules using electrolysis • The chemical bonds within the water molecule are broken • Atoms cannot be chemically separated nor physically separated

  33. Physical Separation of Mixtures • Mixtures can be physically separated using different techniques • Pure substances can NOT be physically separated • Physical separation techniques use differences in properties to separate the substances

  34. Distillation Distillation uses differences in the boiling points of substances to separate a solution into its components.

  35. Filtration In filtration solid substances are separated from liquids and solutions. Filtration uses differences in size to separate components.

  36. Chromatography This technique separates substances on the basis of differences in properties including size, solubility (ability to dissolve), boiling point, and/or mass.

  37. Energy • Energy is the ability to do work or produce heat • Mostly covered in physics • Two types • Kinetic – energy in motion • Potential - stored energy • All chemical reactions require energy to get started • This amount of energy required is called the activation energy (Ea)

  38. Energy • Temperature is a measure of average kinetic energy • Energy can be measured in Joules, Calories, Kilocalories (we use Joules) • Law of Conservation of Energy: energy can be converted from one form to another but can be neither created nor destroyed • When one object or reaction loses energy, that same amount of energy is gained by something else • q is used to represent heat energy • A reaction in which heat is lost or released is considered exothermic • Feels hot, q is negative • A reaction in which heat is gained or absorbed is considered endothermic • Feels cold, q is positive

  39. Energy Diagram • How much energy did this reaction start with? • How much energy did this reaction finish with? • Did this reaction gain or lose energy? How much? • Is this an endothermic or exothermic reaction? • What is the activation energy for this reaction?

  40. Energy Diagram • How much energy did this reaction start with? • How much energy did this reaction finish with? • Did this reaction gain or lose energy? How much? • Is this an endothermic or exothermic reaction? • What is the Eafor this reaction?

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