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Introduction to Chemistry

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  1. Introduction to Chemistry

  2. Matter: is anything that has mass and takes up space

  3. Properties of Matter • Chemistry is the study of the properties of matter and how matter changes • Every form of matter has two kinds of properties physical properties and chemical properties.

  4. Properties of Matter • Physical Property is a characteristic of a pure substance that can be observed without changing it into another substance • Examples: • Color • Texture • States of matter • Size • Temperature • Smell • Shape • Boiling point • Melting point • Density

  5. What are some physical properties?

  6. Chemical Properties of Matter • Chemical property is a characteristic of a pure substance that describes its ability to change into a different substance • Examples: • Burning • rusting • Film processing

  7. Elements • Elements are the simplest pure substance • Elements are often called the building blocks of matter because all matter is composed of one or more element or a combination of two or more elements.

  8. Particles of Elements- Atoms • An atom is the basic particle from which all elements are made. • DIFFERENT ELEMENTS HAVE DIFFERENT PROPERTIES BECAUSE THEIR ATOMS ARE DIFFERENT!!

  9. When Atoms Combine • The majority of element’s atoms combine with other atoms. • When atoms combine, they form a chemical bond—which is the force of attraction between two atoms.

  10. In many cases, atoms combine to form larger particles called molecules

  11. Compounds • A compound is a pure substance made of two or more elements that are combined in a specific ratio. • Example: • Sodium chloride (table salt)

  12. When elements are chemically combined, they form compounds having properties that are different from those of the uncombined elements.

  13. Mixtures • A mixture is two or more substances-elements, compounds, or both—that are in the same place but not chemically combined. • Examples: • Gasoline • Soil • Air

  14. Heterogeneous mixtures– you can see the different parts • Homogeneous mixtures – substances are mixed evenly

  15. Changes In Matter Chapter One Section Three

  16. Physical Change • A physical change is any change in the form or appearance of matter but does not change the substance.

  17. A substance that undergoes a physical change is till the same substance after that change

  18. Types of Physical Changes • Changes of state- moving from between solids, liquids, and gases. • Changes in Shape or form

  19. Chemical Change • A change in matter that produces one or more new substance is a chemical change • A chemical change produces a new substance with properties that are different from those of the original substance.

  20. Conservation of Mass • The fact that matter is not created nor destroyed in any chemical or physical change is called The law of conservation of mass

  21. No mass is lost, because during a chemical change, atoms are not lost or gained, only rearranged

  22. Matter and Energy • Energyis the ability to do work or cause change. • Every chemical or physical change in matter includes a change in energy.

  23. Temperature and Thermal Energy • Temperature is the measure of the average energy of random motion of particles of motion. • Thermal energy is the total energy of all of the particles in an object. • Thermal energy always flows from warmer to cooler areas

  24. Thermal Energy and Changes in Matter • Endothermic energy – a change in which energy is taken in or absorbed ( substance gets cold) • Exothermic Energy – when energy is given off (substance gets warm)

  25. Introduction to Atoms Chapter three section one

  26. Structure of an Atom • What is an element? • A pure substance that cannot be broken down into other substance by chemical of physical means • What is an atom? • The basic particle from which all elements are made up. •

  27. Structures of an Atom

  28. Particles of Atoms • An atom consists of a nucleus surrounded by one or more electrons. • Neutronfound in the nucleus of an atom (has no charge) • Protons found in the nucleus, have a positive electric charge (+) • Electronsmove rapidly around the nucleus and have a negative charge (e-)

  29. Particles of an Atom

  30. A Cloud of Electrons • Electrons move within a sphere shaped region surrounding the nucleus. • Electrons with lower energy usually move in the space near the atom’s nucleus. • Electrons with higher energy move within the space farther from the nucleus.

  31. A Cloud of Electrons

  32. A Cloud of Electrons • Most of the atom’s volume is the space in which electrons move. • The space is huge compared to the amount of space taken by the nucleus. •

  33. Comparing Particle Masses • Electrons take up the majority of space in the atom but they account for very little of the mass. • It takes about 2,000 electrons to equal the mass of just one proton. • Together the proton and the neutrons make up nearly all the mass of an atom.

  34. Comparing Particle Masses • Atoms are too small to be measured in everyday units of mass, such as grams or kilograms. • Scientists use atomic mass units (amu) to measure the mass of an atom.

  35. Comparing Particle Masses

  36. Atomic Number • An element can be identified by the number of protons in the nucleus of its atoms • Every atom of an element has the same number of protons. • Each element has a unique atomic number – the number of protons in its nucleus.

  37. Isotopes • Atoms with the same number of protons but different numbers of neutrons are called isotopes • An isotope is identified by its mass number which is the sum of the protons and neutrons in the nucleus of an atom

  38. Ion • An atom where the total number of protons is not equal to the total number of electrons is an Ion • Results in a overall positive or negative charge

  39. Modeling Atoms • One speck of dust may contain about one million billion atoms!!!!!!!!!! • Because atoms are so small, scientists create models to describe them. • Model-may be a diagram, a mental picture, a mathematical statement, or an object that helps explain ideas about the natural world.

  40. Modeling Atoms • In chemistry, models of atoms are used to explain how matter behaves. • The modern atomic model explains why most elements react with other elements, while a few elements hardly reacts at all.

  41. Organizing the Elements Chapter three section two

  42. Pattern in the Elements • By 1869 there were 63 known elements. Each of these elements have different chemical and physical properties. • A Russian scientist, Dmitri Mendeleev, discovered a set of patterns that applied to all the elements in order to organize the elements. •

  43. Mendeleev’s Work

  44. Mendeleev’s Work • Elements have similar chemical and physical properties. • Example: • Fluorine and Chlorine –gases that irritate the skin • Silver and Copper – shinny metals that tarnish if exposed to air.

  45. Mendeleev’s Work • Mendeleev started organizing elements by their color, density, melting point, atomic mass, and the number of chemical bonds the element can form. • The atomic massof an element is the average mass of all the isotopes of that element.

  46. Mendeleev’s Work • He noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass

  47. Mendeleev’s Periodic Table