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Basic Chemistry. Matter. Matter- is anything that takes up space. Each kind of matter has specific properties, or characteristics, that distinguish it from every other kind of matter. Physical Properties of Matter.
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Matter • Matter- is anything that takes up space. • Each kind of matter has specific properties, or characteristics, that distinguish it from every other kind of matter.
Physical Properties of Matter • Physical properties- are characteristics that can be determined without changing the basic makeup of the substance.
Chemical Properties of Matter • Chemical properties- describe how a substance acts when it combines with other substances to form an entirely different substance, with new properties.
Atoms • Atoms- are the basic building blocks of matter. • Atomic structure of an atom consists of a nucleus and electron cloud.
Atomic Structure • Nucleus- central core of the atom, consists of two types of subatomic particles: protons (p+) carry a positive electrical charge of +1, and electrically neutral neutrons (no). The nucleus thus has an overall positive charge.
Atomic Structure • Electron cloud- the region or space around the nucleus that is occupied by rapidly moving particles that are negatively charged, called electrons (e-).
Ions • Ion- atom that has gained or lost one or more electrons. • Anion- atoms that have gained electron(s) and are now negative ions (Cl-, F-) • Cation- atoms that have lost electron(s) and are now positive ions (H+, Na+)
Ionic Bonds- formed when one or more electrons are transferred from one atom to another • Forms ions- positively or negatively charged atoms resulting from the gain or loss of electrons
Sodium How many valence electrons does sodium have?
Chlorine • How many electrons in Chlorine’s valence shell?
If Na has one electron to give, and Cl needs another electron, both would be more stable if Na gave Cl its electron. • What would happen to the charges of both atoms? • Na is losing a negative charge (11+, 10-) so net charge of +1 • Cl is gaining a negative electron, so it has a charge of –1 • We write these charges as Na+ and Cl- • These are IONS. • What happens between positive and negative charges? • THEY ATTRACT– Forming an IONIC BOND
Elements • Elements- substance composed of one type of atom, that can not be changed into a simpler substance by chemical means. • The number of protons in the nucleus determines the type of atom/element, and the number of protons in a given element is always constant.
Elements • There are 92 naturally occurring elements. Example: Carbon, you can heat it etc., but it will NOT turn into anything other than carbon.
Elements • About 25 elements are essential to life: • 96% of all matter is made of C, O, H, and N • The remaining 4% is made up mostly of P, S, Ca, and K. Trace elements—those required by organisms in minute quantities(less than 0.01%) Ex: Fe, I, B, Cr, Co, Mn, Zn
Elements (cont.) • Symbols- a simple, standard, abbreviated way of referring to elements. Usually one letter, sometimes two letters, but the second letter is not capitalized. Ex. H = hydrogen, Na = sodium
Elements (cont.) • Isotopes- are atoms of the same element with different numbers of neutrons. Isotopes do have the same chemical properties.
Elements (cont.) • Radioactive Isotopes- isotopes with unstable nuclei that break down at a constant rate over time. As a result, they give off radiation which can be harmful. But they can also be used as “labels” or “tracers.”
Chemical Formulas • Chemical Formula- a group of symbols that show what type and how many atoms are present in a compound.
Chemical Formulas • Subscripts tell how many of each atom is present. No subscript it is understood to represent one atom. • Ex. H2O = 2 Hydrogen atoms and 1 Oxygen atom • Coefficients, a number in front of the entire formula, represents how many molecules you have. • Ex. 2H2O = 2 molecules of water • To find out the number of atoms in more than one molecule, multiply each subscript by the number in front of the formula. • Ex. 2H2O = 4 Hydrogen atoms and 2 Oxygen atoms
Compounds • Compounds- are two or more elements that are chemically combined. Each compound has its own special properties, which differ from the properties of the individual elements within that compound. • Ex. Chlorine (poisonous gas) combined with sodium = sodium chloride (table salt).
Molecules • Molecules- The smallest particle of a compound or element that can have stable, independent existence.
Molecules • A molecule of a compound contains two or more different atoms. • When atoms combine to form molecules a molecule of an element may consist of one, two or more atoms of that element. • Their outer energy levels become more stable. • One way of filling their energy levels is by sharing electrons. The electrons then move in the region between and around the nucleus.
Chemical Bonds • Chemical bonds- forces holding atoms in any molecule or compound together. • Chemical bonds result from the interaction of electrons in the outer energy levels of atoms.
Ionic Bonds • Ionic Bonds- electrical attraction between positively and negatively charged ions (atom that has gained or lost one or more electrons). The resulting charge of an Ionic Compound will be zero or neutral.
Ionic Bonds Example: Sodium and Chlorine combine to make salt. Sodium atom transfers its single outer electron to the chlorine atom. Transfer gives each atom a stable outer energy level of eight electrons.
Covalent Bonds • Covalent Bonds- when atoms combine to form a molecule by sharing electrons. • Single covalent bond- atoms share 2 electrons • Double covalent bond- atoms share 4 electrons
Covalent Bonds • Example: Methane (CH4 ) The Carbon atom has 4 electrons in its outer energy level, it need 4 more for a stable outer level. Each of the 4 Hydrogen atoms shares its single electron with the carbon atom, completing the carbon’s outer level. At the same time, the carbon atom shares one of its electrons with two of the hydrogen atoms. Altogether 6 electrons are shared in a methane molecule- one contributed by each hydrogen atom and two contributed by the carbon atom.
Hydrogen Bonds Hydrogen Bonds: slight attractions that develop between the oppositely charged regions of nearby molecules. Although these forces are not as strong as ionic or covalent bonds, they can hold molecules together, especially when the molecules are large. Individual these bonds are weak and short lived, but collectively they are very strong.
Van der Waals Interactions • Van der Waals Interactions are weak attractions between molecules or parts of molecules that are brought about by localized charge fluctuations. • INTERmolecular bond- in between molecules
Chemical Equations • Chemical Equations are mathematical ways to represent chemical reactions. Ex. C + 4H CH4 Reactants Products If 4H’s are shown in the products, they must be found in the reactants.
Chemical Reactions • Chemical reactions are due to the making and breaking of chemical bonds leading to a change in the composition of matter. Ex: formation of H2O Reactants—starting materials Products—results Matter is conserved in a chemical reaction…Law of Conservation of Matter.
Mixtures • Mixture- is the molecules of different substances mingling together (physically) with out chemically combining. Each substance retains all its chemical properties and its physical properties, which makes it possible to separate them physically. • Mixtures can contain solids, liquids and gases.
Solutions • Solutions- are mixtures that are the same throughout, but have variable compositions, depending on how much of one substance is dissolved in the other.
Solutions • Two Parts of a Solution: • Solvent- the substance that can dissolve other substances. Water is often called the “Universal Solvent.” • Solute- the substance that dissolves in the solvent. • Examples: Salt Water: Water is the solvent and Salt is the solute. Kool Aid: Water is the solvent and Sugar is the solute.
Solutions • Concentration- the amount of solute dissolved in a given amount of solvent. • Molarity- the moles of solute per liter of solution. A 1.0 molar solution of sucrose will contain 1 mole (6.02 x 1023 molecules) of sugar in each liter of solution.
Mixtures of water and non-dissolved materials that are in pieces so small that the movement of water molecules does not allow them to settle out but keeps them “suspended.” Blood is an example of a suspension. Suspensions
Water and The Fitness of the Environment • Overview: The Molecule That Supports All of Life • Water is the biological medium here on Earth • All living organisms require water more than any other substance
Figure 3.1 Water, not Earth • Three-quarters of the Earth’s surface is submerged in water • The abundance of water is the main reason the Earth is habitable
Water is Polar • The water molecule is a polar molecule: • Oxygen is significantly more electronegative than hydrogen. • Although oxygen and hydrogen share electrons, oxygen does not share fairly…it keeps the electrons more of the time. • Water can form four hydrogen bonds with neighboring molecules.
– Hydrogenbonds + H – + H + – – + Figure 3.2 Polarity of Water • The polarity of water molecules allows them to form hydrogen bonds with each other and contributes to the various properties water exhibits. These are not as strong as ionic or covalent.
Water and Life Emergent properties of water due to its polarity contribute to Earth’s fitness for life
Water molecules exhibit cohesion Cohesion is the bonding of a high percentage of the molecules to neighboring molecules. It is due to hydrogen bonding. Water is extremely cohesive Explains why drops of water “beads up” on a smooth surface Allows water striders to walk on surface of water Cohesion
Water conducting cells 100 µm Figure 3.3 • Cohesion helps pull water up through the microscopic vessels of plants
Adhesion • Attraction between molecules of different substances • Explains the dip in water level when reading a graduated cylinder
Figure 3.4 • Surface tension is a measure of how hard it is to break the surface of a liquid. It is related to cohesion.
Moderation of Temperature • Water moderates air temperature by absorbing heat from air that is warmer and releasing the stored heat to air that is cooler
