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CHEMISTRY. Composition of Matter Matter - Everything in universe is composed of matter Matter is anything that occupies space or has mass Mass – quantity.

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Presentation on theme: "CHEMISTRY. Composition of Matter Matter - Everything in universe is composed of matter Matter is anything that occupies space or has mass Mass – quantity."— Presentation transcript:


2 Composition of Matter Matter - Everything in universe is composed of matter Matter is anything that occupies space or has mass Mass – quantity of matter an object has Weight – pull of gravity on an object

3 Atoms The simplest particle of an element that retains all the properties of that element Properties of atoms determine the structure and properties of the matter they compose Our understanding of the structure of atoms based on scientific models, not observation

4 The Nucleus Central core Consists of positive charged protons and neutral neutrons Positively charged Contains most of the mass of the atom

5 The Electrons Negatively charged high energy particles with little or no mass Travel at very high speeds at various distances (energy levels) from the nucleus

6 Elements Pure substances that cannot be broken down chemically into simpler kinds of matter More than 100 elements (92 naturally occurring)

7 90% of the mass of an organism is composed of 4 elements (oxygen, carbon, hydrogen and nitrogen) Each element unique chemical symbol Consists of 1-2 letters First letter is always capitalized

8 The Protons All atoms of a given element have the same number of protons Number of protons called the atomic number Number of protons balanced by an equal number of negatively charged electrons

9 Atomic Mass Protons & neutrons are found in the nucleus of an atom Protons and neutrons each have a mass of 1 amu (atomic mass unit) The atomic mass of an atom is found by adding the number of protons & neutrons in an atom

10 Electrons in the same energy level are approximately the same distance from the nucleus Outer energy levels have more energy than inner levels Each level holds only a certain number of electrons

11 The Neutrons The number varies slightly among atoms of the same element Different number of neutrons produces isotopes of the same element

12 Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state Some molecules are large and complex

13 A compound is a pure substance made up of atoms of two or more elements The proportion of atoms are always fixed Chemical formula shows the kind and proportion of atoms of each element that occurs in a particular compound

14 Chemical Formulas Subscript after a symbol tell the number of atoms of each element H 2 0 has 2 atoms of hydrogen & 1 atom of oxygen Coefficients before a formula tell the number of molecules 3O 2 represents 3 molecules of oxygen or (3x2) or 6 atoms of oxygen

15 Compounds Most elements do not exist by themselves Readily combine with other elements in a predictable fashion

16 The tendency of elements to combine and form compounds depends on the number and arrangement of electrons in their outermost energy level Atoms are most stable when their outer most energy level is filled

17 Most atoms are not stable in their natural state Tend to react (combine) with other atoms in order to become more stable (undergo chemical reactions) In chemical reactions bonds are broken; atoms rearranged and new chemical bonds are formed that store energy

18 Ionic Bonds Some atoms become stable by losing or gaining electrons Atoms that lose electrons are called positive ions

19 Atoms that gain electrons are called negative ions Because positive and negative electrical charges attract each other ionic bonds form

20 Covalent Bonds Formed when two atoms share one or more pairs of electrons

21 Energy and Chemical Reactions Living things undergo thousands of chemical reactions as part of the life process

22 Many are very complex involving multistep sequences called biochemical pathways Chemical equations represent chemical reactions Reactants are shown on the left side of the equation Products are shown on the right side

23 The number of each kind of atom must be the same on either side of the arrow (equation must be balanced) Bonds may be broken or made forming new compounds

24 Acids and Bases One of the most important aspects of a living system is the degree of acidity or alkalinity

25 Acids Number of hydronium ions in solutions is greater than the number of hydroxide ions HCl  H + + Cl -

26 Bases Number of hydroxide ions in solution is greater than the number of hydronium ions NaOH  Na + + OH -

27 the lower the pH the stronger the acid the higher the pH the stronger the base pH 7.0 is neutral

28 pH Scale logarithmic scale for comparing the relative concentrations of hydronium ions and hydroxide ions in a solution ranges from 0 to 14  Each pH is 10X stronger than next  e.g. ph 1 is 10 times stronger than ph 2

29 Buffers Control of pH is very important Most enzymes function only within a very narrow pH Control is accomplished with buffers made by the body Buffers keep a neutral pH (pH 7)

30 Buffers neutralize small amounts of either an acid or base added to a solution Complex buffering systems maintain the pH values of your body’s many fluids at normal and safe levels

31 Energy and Matter Energy The ability to do work or cause change Occurs in various forms Can be converted to another form Forms important to biological systems are chemical, thermal, electrical and mechanical energy Free energy is the energy in a system that is available for work

32 Energy Transfer Much of the energy organisms need is provided by sugar (food) Undergoes a series of chemical reactions in which energy is released (cell respiration) The net release of free energy is called an exergonic (exothermic) reaction

33 Reactions that involve a net absorption of free energy are called endergonic (endothermic) reactions Photosynthesis is an example Most reactions in living organisms are endergonic; therefore living organisms require a constant source of energy

34 Most chemical reactions require energy to begin The amount of energy needed to start the reaction is called activation energy

35 Certain chemical substances (catalysts) reduce the amount of activation energy required Biological catalysts are called enzymes

36 Enzymes are an important class of catalysts in living organisms Mostly protein Thousands of different kinds Each specific for a different chemical reaction

37 Enzyme Structure Enzymes work on substances called substrates Substrates must fit into a place on an enzyme called the active site Enzymes are reusable!

38 Solutions

39 Solutions A solution is a mixture in which 2 or more substances are uniformly distributed in another substance

40 Solute is the substance dissolved in the solution Particles may be ions, atoms, or molecules Solvent is the substance in which the solute is dissolved Water is the universal solvent

41 Solutions can be composed of varying proportions of a given solute in a given solvent --- vary in concentration (measurement of the amount of solute) A saturated solution is one in which no more solute can be dissolved Aqueous solution (water) are universally important to living things

42 Dissociation of water Breaking apart of the water molecule into two ions of opposite charge (due to strong attraction of oxygen atom of one molecule for H atom of another water molecule) H 2 O  H + (hydrogen ion) + OH - (hydroxide ion) H + + H 2 O  H 3 O (hydronium ion)

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