Presentation on theme: "Basic Chemistry Chapter 2 Pages 25-39. Concepts of Matter and Energy _____________– anything that occupies space and has mass (weight). – Chemistry studies."— Presentation transcript:
Basic Chemistry Chapter 2 Pages 25-39
Concepts of Matter and Energy _____________– anything that occupies space and has mass (weight). – Chemistry studies the nature of matter and how its building blocks interact – May be __________________________________ – May be changed physically and chemically Physical changes do not alter the nature of the substance Chemical changes do alter the composition of the substance
Energy Energy – has no mass, does not take up space. Defined as the ability to do work or put matter in motion _________________energy – energy doing work by moving matter _________________energy- energy that is stored, inactive and at the moment, not doing work All forms of energy exhibit both kinetic and potential work capacities
Forms of Energy ________________ Energy – stored in the bonds of chemicals (potential) – Breaking bonds releases kinetic energy _________________Energy – results from movement of charged particles – In physiology, electrical energy results when ions cross membranes __________________Energy – Energy directly involved in moving matter – Example: Your muscles pulling on bones allowing movement __________________ Energy – Travels in waves – Examples: light, sound, x-rays, gamma-rays, radio, UV, infrared
Energy Form Conversions Energy may be changed from one form to another easily Energy cannot be destroyed or created Some energy conversions are very inefficient and much energy is “lost” or unusable – Ex: When a light bulb is on for an hour, most of the electrical energy is converted to light but some of the electrical energy is converted to heat and is unusable. We are warm-blooded because many of our chemical reactions release heat – This is important for many of our chemical reactions. As molecules heat up, they increase the speed at which they move, thus increasing their kinetic output
Did you get it? 1.Matter and energy – how are they interrelated? 2.What form of energy is used to transmit messages from one part of the body to another? 3.What type of energy is available when we are still? When we are exercising? 4.What does it mean when we say that some energy is “lost” every time energy changes from one form to another in the body?
Composition of Matter Elements – unique substances that cannot be broken down into simpler substances because they are made of one type of _________(building block) – Currently, 92 exist in nature. Including man-made elements, there are at least 112, maybe 118 – 96% of human body weight is made of only four elements: Carbon, Hydrogen, Nitrogen and Oxygen Each element is designated by one or two letters, known as the ____________________________
Atomic Structure Each atom is composed of: – ___________________(positive and in nucleus) – P + – ___________________(neutral and in nucleus) – N 0 – ___________________(negative and orbiting nucleus) – e - Each element is defined by the number of protons in the nucleus. This is called the atomic number Most atoms are electrically neutral thus the number of protons (never changing) is usually the same as the number of ____________________________ When atoms gain or lose and electron, they become positive or negative _____________
Planetary and Orbital Models __________________________model: each atom is like a mini universe. The dense nucleus is made of heavy protons and neutrons, while the lighter electrons fly around in circular patterns. Because the electrons may skip from one path to another, scientists call the general location they are likely to be, “orbitals.” __________________________model: more modern. The general location of electrons surrounding the nucleus is referred to as the “electron cloud.” A hazy area of negative charge Either way… the behavior of the electrons as they move in their orbitals, determines the behavior of the atom.
Identifying Elements: Review Atomic Number: the unique ID number. Determined by the number of protons which will never change for each element. Atomic mass: the sum of the masses of protons and neutrons in the nucleus. Written as a superscript to the left of the atomic symbol – Usually the atomic mass is twice the atomic number. However, if more or less neutrons exists, the mass is changed. These are called isotopes.
Radioisotopes continued Heavier isotopes of some elements are unstable and tend to decompose to become more stable. These are called ___________________________________. The spontaneous decay of these elements is called _______________________________and involve rejection of particles from the atoms. The particles emitted may be alpha, beta or gamma particles. Alpha = weakest, gamma = ______________________ This emission of energy is damaging to living cells. – These particles act like bowling balls knocking through electrons of other atoms causing disruption of atom function. – While overexposure to radiation is harmful, in small doses, biologists can use radioisotopes to tag biological molecules and follow their activity in the body. In other words, radioisotopes may be a powerful diagnostic tool
Molecules ___________________= 2 or more atoms combined of the same or different atoms – Ex: H + H = H 2 (molecular hydrogen) ___________________= 2 or more atoms combined from different elements – Ex: 4H + C = CH 4 (Methane) Compounds have very different properties than the atoms they are made of individually – Ex: Chlorine and Sodium vs. Table Salt
Bonding Electrons are found orbiting the nucleus in “electron shells” So far, we know of seven shells in which electrons closest to the nucleus are the most strongly attracted and least likely to react (shell 1), whereas those farthest away are weakly attracted to the nucleus and most likely to react with nearby atoms Each shell can hold a specific number of electrons – Shell 1: 2 electrons – Shell 2: 8 electrons – Shell 3: 18 electrons The outermost shell is the __________________________. – Typically holds up to 8 electrons (inert) – If there are less than 8 in the valence shell, the atom will tend to gain, lose or share electrons 2 atoms may react when their valence shells overlap
Types of Bonds _________________: electrons are completely transferred from one atom to another – Cations are (+) charged ions formed when atoms lose electrons during the bond formation – Anions are (-) charged ions formed – Ionic compounds typically form salts and result from bonding between a metal and non-metal _________________: electrons are shared between valence shells of two atoms – ___________________molecules form when part of the molecule is slightly positive (δ + ) and another portion is slightly negative (δ - ). These molecules tend to orient themselves near other polar molecule with very weak magnetic forces
Bonds Continued _________________________bonds: weak bond formed between the hydrogen of one atom and a nitrogen or oxygen of another atom. – Especially important with regard to water behavior – ___________________: Water molecules attracted to each other – ___________________: water molecules attracted to a different molecule These bonds are very important in many biological reactions They may form intramolecular bonds in which they hold different portions of the same molecule together – Ex: Important in protein folding
Patterns of Chemical Reactions The number of atoms does not change during a reaction. They are simply rearranged. ______________________reactions: two or more atoms/molecules combine to form larger molecules ______________________(digestion) reactions: a molecule is broken down into smaller molecules/atoms ______________________reactions: involve synthesis and digestion. A switch is made between molecule parts – Ex: Glucose + ATP Glucose-P + ADP Most reactions are reversible (indicated by a double arrow) – A longer arrow indicates a more rapid reaction – Equal arrow length indicates chemical equilibrium