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What is CHEMISTRY ?

1. What is CHEMISTRY ?. What is CHEMISTRY ?. CHAPTER. The Study of Matter and its Properties, the Changes that Matter Undergoes, and the Energy Associated with those Changes. 1. Major Chemistry subdivisions. CHAPTER. Analytical (qualitative and quantitative) Chemistry:

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What is CHEMISTRY ?

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  1. 1 What is CHEMISTRY ? What is CHEMISTRY ? CHAPTER The Study of Matter and its Properties, the Changes that Matter Undergoes, and the Energy Associated with those Changes

  2. 1 Major Chemistry subdivisions CHAPTER • Analytical (qualitative and quantitative) Chemistry: • Qualitative Analytical Chemistry: What is a sample of matter composed of? • Quantitative Analytical Chemistry: How much “stuff” is in a sample of matter? • Physical Chemistry: The study of the physics involved with chemical changes. • Organic Chemistry: The study of properties and reactions of compounds that contain Carbon • Inorganic Chemistry: The study of properties and reactions of compounds that are not Carbon based • Biochemistry: The study of living systems (Biology + Chemistry)

  3. 1 Chemistry: The Study of Change CHAPTER Levels of Operation From experiment to modelling “Chemists communicate their observations and ideas with each other through words, labels, drawings and symbols to refer to particular events and substances”

  4. 1 Chemistry: The Study of Change Classifying Matter CHAPTER • Matter is defined as: Anything that occupies space and has mass • The classification of matter include substances, mixtures, elements, and compounds, as well as atoms and molecules. • Mass: The quantity of matter in a material. • Law of Conservation of Mass: • The total mass remains constant during a chemical change (chemical reaction).

  5. 1 Chemistry: The Study of Change States of Matter CHAPTER Solid: characterized by rigidity; fixed volume and fixed shape. Liquid: relatively incompressible fluid; fixed volume, no fixed shape. Gas: compressible fluid; no fixed volume, no fixed shape. Particles are closely packed and vibrate about fixed positions Particles are not in fixed positions and can move past one another Particles are not in fixed positions and can move past one another

  6. 1 Chemistry: The Study of Change Classifying Matter CHAPTER • Substance: is a single, pure form of matter • Example: water, copper, sugar, Oxygen and gold • Or, A kind of matter that cannot be separated into other kinds of matter by any physical process such as distillation or sublimation. • Mixtures contain two of more substances mixed together • Example: air, steel, soda-cola, saltwater, salad dressing • Mixtures can be: • Homogeneous mixtures • Heterogeneous mixtures

  7. 1 Chemistry: The Study of Change Classifying Matter CHAPTER • Homogeneous and heterogeneous mixtures A solution of salt in water is a homogeneous mixture or sugar dissolves in water , The sample has a uniform composition throughout Noodle soup is a heterogeneous mixture Materials are not uniformly dispersed over the whole sample

  8. 1 Chemistry: The Study of Change CHAPTER Elements and their Atoms Element: A substance that cannot be decomposed into simpler substances by any chemical reaction. • There are only 118 (so far) known elements • 90 elements are found in nature, the rest have been made in the laboratory Example of elements:

  9. 1 Chemistry: The Study of Change CHAPTER Compounds and Molecules A molecule is formed when two or moreatoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds. Molecules H2 O2 Compounds NaCl CH4 CaCl2

  10. 1 Chemistry: The Study of Change CHAPTER Compounds • A CHEMICAL COMPOUND is a substance composed of atoms of two or more different elements. H2O or CO2 • A combination of atoms represents a MOLECULE or ION, which is characteristic for each compound • Molecules or ions are composed of atoms in fixed and definite proportions • Compounds have properties which are different than properties of elements they are made from

  11. 1 Chemistry: The Study of Change CHAPTER Compounds EXAMPLE: Sodium (metal) and chlorine (gas) will react to produce sodium chloride NaCl (table salt – colourless, crystalline substance):

  12. 1 Chemistry: The Study of Change CHAPTER Compounds • A CHEMICAL FORMULA shows the composition of a compound • It features the relative numbers of different types of atoms EXAMPLE: NaCl Sodium chloride contains the same number of atoms of sodium and chlorine combined in a molecule Na Cl

  13. 1 Chemistry: The Study of Change Classifying Matter CHAPTER • Kinetic-molecular model of matter • Particles: atoms, molecules or ions • Motion of particles opposed by the forces of attraction between particles SOLID LIQUID GAS Forces of attraction dominate Fast motion of particles due to the increase in kinetic energy. Resulting forces overcome forces of attraction Temperature increases

  14. 1 Chemistry: The Study of Change Aluminum powder burns in oxygen to produce a substance called aluminum oxide. A sample of 2.00 grams of aluminum is burned in oxygen and produces 3.78 grams of aluminum oxide. How many grams of oxygen were used in this reaction? CHAPTER Chemical Reactions, Chemical Change aluminum + oxygen = aluminum oxide 2.00 g + oxygen = 3.78 g oxygen = 1.78 g

  15. Comparison of Physical and Chemical Properties

  16. 1 Chemistry: The Study of Change CHAPTER Introduction • Classification of Matter • Matter is anything that occupies space and has mass. The classification of matter include substances, mixtures, elements, and compounds, as well as atoms and molecules. • Substances and Mixtures: • A Substance is a form of matter that has a definite (constant) composition and distinct properties. Examples are water, ammonia, gold and oxygen. • A Mixture is a combination of two or more substances in the substances retain their distinct identities. Examples are air, and cement. • Mixtures are either homogeneous or heterogeneous. When a spoonful of sugar dissolves in water we obtain a homogenous mixture in which the composition of the mixture is the same throughout. If sand is mixed with iron filings, however, the sand grains remain separate. This type of mixture is called a heterogeneous mixture because the composition is not uniform.

  17. Any type of mixture, can be created and then separated by physical means into pure component. Solution: Is a homogeneous mixture and its components called : Solute : it is the existent substance in a low quantity. Solvent: it is the existent substance in a high quantity. Elements and Compounds An element is a substance that cannot be separated into simpler substances. To date, 117 elements have been identified. Atoms of most elements can interact with one another to form compounds. Hydrogen gas, for example, burns in oxygen gas to form water, which has properties that are different from those of the starting materials.

  18. 1 Chemistry: The Study of Change A measured quantity is usually written as a number with an appropriate unit.Examples20 grams6.63 × 10–34joule·seconds CHAPTER Measurements SI Units In 1960 the General Conference of Weights and Measures, the international authority of units, proposed a revised metric system called international system of units (abbreviated SI . Table 1.2 shows the seven SI base units. All other units of measurements can be derived from these base units. SI units are modified in decimal fashion by a series of prefixes, as shown in table 1.3

  19. 1 Chemistry: The Study of Change CHAPTER Measurements

  20. 1 Chemistry: The Study of Change CHAPTER Measurements femto- f 0.000000000000001 10-15 1 femtometer fm = 1 x 10-15 m

  21. 1 Chemistry: The Study of Change Note that a metric prefix simply represents a number: 1mm = 1 x 10-3 mMeasurements that we will utilize frequently in our study of chemistry include time, mass, volume, and temperature. CHAPTER Measurements

  22. 1 Chemistry: The Study of Change Mass and WeightMass is a measure of the amount of matter in an object, weight, is the force that gravity exerts on an object. An apple that falls from a tree is pulled downward by Earth`s gravity. The mass of the apple is constant and does not depend on its location, but its weight does. Chemists are interested in mass, which can be determined with a balance. The SI unit of mass is kilogram (Kg) 1 Kg + 1000 g = 1 x 103 g CHAPTER Measurement

  23. Volume V = length x width x height = m x m x m = m3The SI unite of length is the meter (m), and that of volume is the cubic meter (m3), the cubic centimeter (cm3) and the cubic decimeter (dm3) 1cm3 = ( 1 x 10-2 m )3 = 1 x 10-6 m3 1dm3 = ( 1 x 10-1 m)3 = 1 x 10-3 m3Another common unite of volume is the liter (L) 1L = 1000 ml = 1000 cm3= 1 dm3 1 mL = 1 cm3.

  24. DensityThe equation for density is The SI-derived unit for density is the kilogram per cubic meter ( kg/m3 ). This unit is large for most chemical applications. Therefore, gram per cubic centimeter (g/cm3) and its equivalent, gram per milliliter (g/mL) are used for solid and liquid densities. 1g/cm3 = 1g/mL = 1000kg/m3Example 1.1A piece of metal with a mass of 200 g has a volume of 17.6 cm3 . Calculate the density of gold. Solution:We are given the mass and volume and asked to calculate the densityExample 1.2The density of mercury, the only metal is a liquid at room temperature, is 13.6 g/ml.calculate the mass of 7.8 mL of the liquid.Solution:

  25. Heat and Temperature • Heat and Temperature are not the same thing • T is a measure of the intensity of heat in a body • 3 common temperature scales - all use water as a reference

  26. Temperature:Three temperature are currently in use. Their units are ⁰F(degrees Fahrenheit). ⁰C (degree s Celsius), and K (kelvin). The fahrenheit scale, defines the normal freezing and boiling points of water to be 32⁰F and 212⁰F, respectively. The Celsius scale divides the range between the freezing point (0⁰C) and boiling point (100⁰C) of water into 100 degrees. The kelvin is the SI base unite of temperature: it is the absolute temperature scale. T e zero on kelvin ( 0 K ) is the lowest temperature can be attained. To convert Fahrenheit we use K = ⁰C + 273,15

  27. Heat and Temperature • MP waterBP water • Fahrenheit 32 oF 212 oF • Celsius 0.0 oC 100 oC • Kelvin 273 K 373 K

  28. Relationships of the Three Temperature Scales

  29. Relationships of the Three Temperature Scales

  30. Relationships of the Three Temperature Scales

  31. Relationships of the Three Temperature Scales • Easy method to remember how to convert from Centigrade to Fahrenheit. • Double the Centigrade temperature. • Subtract 10% of the doubled number. • Add 32.

  32. Temperature Example: Convert 211oF to degrees Celsius. Example: Express 548 K in Celsius degrees.

  33. Example 1.3a) A certain solder (alloy of Tin & lead) has a melting point of 245⁰C. What is its melting point in degrees Fahrenheit?b) Helium has the lowest boiling points of all the elements at -396⁰F. Convert this temperature to degrees Celsius.c) Mercury, the only metal that exists as a liquid at room temperature, melts at -96.5⁰C , convert its melting point to kelvins.Solution:a)245⁰C = ( ⁰F – 32⁰F) x (245⁰C x 9⁰F ÷ 5⁰C ) + 32⁰F = ⁰F (245x 9⁰F ÷ 5 ) + 32⁰ F =473 ⁰F c) K = ⁰C + 273,15 = -38.9 + 273.15 = 234.3 KOther examples in “ summery of G. Chemistry” page 10

  34. Handling NumbersScientific NotationAll numbers can be expressed in the form N x 10nwhere N is a number between 1 and 10 and n, the exponent, is a positive or negative integer(whole number). Any number expressed in this way is said to be written in scientific notation.e.g. 1) Express 568.762 in scientific notation 568.762 = 5.68762 x 1022) Express 0.00000772 in scientific notation 0.00000772 = 7.72 x 10-6

  35. Significant Figures • Any digit that is not zero is significant • 1.234 kg 4 significant figures • Zeros between nonzero digits are significant • 606 m 3 significant figures • 16.07 4 sig figs. • Zeros to the left of the first nonzero digit are not significant • 0.08 L 1 significant figure

  36. Significant Figures • If a number is greater than 1, then all zeros to the right of the decimal point are significant • 2.0 mg 2 significant figures • If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant • 0.00420 g 3 significant figures

  37. Trailing zeros are zeros at the right end of the number. They are significant only if the number contains a decimal point. • 9.300 has 4 sig figs. • 150 has 2 sig figs. • 1000000 1 sig figs. • 1.000000 7 sig fig

  38. Significant Figures • Exact numbers: have an INFINITE number of significant figures. This rule applies to numbers that are definitions. • For example, 1 meter = 1.00 meters = 1.0000 meters = 1.0000000000000000000 meters, etc.

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