Presentation on theme: "Chapter 2. Introduction to “Baby Chemistry” Life depends on chemistry We need to be able to understand the chemistry before we move on to understand."— Presentation transcript:
Introduction to “Baby Chemistry” Life depends on chemistry We need to be able to understand the chemistry before we move on to understand the rest of body
Atom - the basic unit of matter Atoms are made of 3 subatomic particles 1. Protons - positive charge 2. Neutrons – neutral charge 3. Electrons – negative charge
Protons and neutrons are found in the atoms nucleus - The center of the atom Electrons are found outside the nucleus Electron cloud They are in constant motion Are attracted to positive charge of nucleus but remain outside due to energy of motion
What is the overall charge of the nucleus? What is the overall charge of the electron cloud? Nucleus (+) & Electron Cloud (-) Therefore, atoms are neutral from equal numbers of protons and electrons
Elements – pure substances that consist of entirely 1 type of atom They are represented by 1, 2 or 3 letters There are 117 elements (periodic table in back of book) Based on certain characteristics of each element
Periodic table includes information on atomic mass and atomic number Atomic Number – number of protons (and therefore electrons) Atomic Mass – sum of protons and neutrons
Q) How are isotopes different? A) They have a different number of neutrons Isotopes are identified by their atomic mass number (protons + neutrons) All isotopes still have the same chemical properties (because neutrons are neutral)
Have nuclei that are unstable and break down at constant rates over time Important Uses 1. Determine age of rocks 2. Treat cancer and kill bacteria that cause food to spoil 3. Used as “tracers” to follow substances in the body
*In nature, most elements are found combined with other elements in compounds Compound – substances formed by the chemical combination of 2 or more elements
What information is contained in a chemical formula? 1. Type of atoms 2. How many of those atoms Example) Q) What’s in H 2 0? A) 2 hydrogen and 1 oxygen
Physical and chemical properties of a compound are usually different from those of elements from which they are formed Example – NaCl Sodium Chloride : Table Salt Sodium (Na) – silver colored metal Chlorine (Cl) – greenish gas +=
Hold compounds together Involves the outer electrons (valence electrons) that surround each atom’s nucleus 3 types of bonds 1. Ionic (strongest) 2. Covalent 3. Van Der Waals Forces (weakest)
One or more electron is “transferred” from one atom to another An atom that loses an electron has a positive charge An atom that gains an electron has a negative charge Positively or negatively charged atoms are called ions
When electrons are “shared” instead of being “transferred” How do they share electrons? The electron travels in the orbits of both atoms Single bond – 2 electrons shared Double bond – 4 electrons shared Triple bond – 6 electrons shared
Atoms joined by covalent bonds are called molecules Water Molecule
Atoms in covalent bond don’t always share equally Rapid movement of electrons creates “+” and “-” charges When molecules are close together, an attraction can occur between oppositely charges region Creates intermolecular “Vander Waals Forces”
How does the gecko’s foot function similarly to Van Der Waals Forces?
The water molecule – H 2 O (think mickey mouse)
Water is a polar molecule What is polarity? The uneven distribution of electrons which causes the molecule to have regions with a positive and negative charge Allows water to attract to other molecules
Most abundant compound in living things Naturally occurring and found at any temperature on the earth Water expands when it freezes, SO WHAT?? How does that affect us?
Held together by hydrogen bonds (not as strong as ionic or covalent) which form between the hydrogen and oxygen Why would this be important? How many bonds are there per water molecule?
Allows 4 bonds to form This bonding pattern is what makes water responsible for it’s many special properties
Cohesion An attraction between water molecules Why can a spider walk on water How does water come out of a faucet?
Adhesion An attraction of water to other molecules How does a tree get water from its roots to its leaves? Why does the water level in a graduated cylinder look curved?
Mixture – a material composed of 2 or more elements or compounds that are physically combined, but not chemically combined Examples: Chocolate Chip Cookie Earths Atmosphere 2 types of Mixtures 1. Solution 2. Suspension
Is a mixture of 2 or more substances in which the molecules are evenly distributed Example: Salt dissolving in water (the NaCl and H 2 O combine by the Cl - being attracted to the H and the Na + being attracted to the O)
2 important terms to know Solute – substance being dissolved Solvent – substance doing the dissolving Q) Why is water considered the greatest solvent in the world? A) Polarity allows it to pull other molecules apart
Concentrations for hydrogen (H + ) and hydroxide (OH - ) ions are important indicators of the properties of a solution A measurement system was created to indicate the concentration of the H + ions in the solution called the pH scale pH – potential of hydrogen A pH of 7 = equal number of H + and OH - ions
H + + OH - = H 2 O Solutions with a pH < 7 are called acids Because more hydrogen ions (H + ) The lower the pH, the greater the acidity
Solutions with a pH > 7 are called alkaline or basic Because more hydroxide (OH - ) ions The higher the pH, the more basic the solution
Each step of the pH scale represents a factor of 10 Ex) pH of 4 has 10x as many H + ions as a solution with a pH of 5 AcidsBases I-------------------------I-------------------------I 1 H + > OH - 7 H + < OH - 14 H + = OH -
Weak acids or bases that can react with strong acids or bases to prevent sharp, sudden changes in pH Why are buffers important? The pH of fluids within most cells of the human body must generally be kept between 6.5 and 7.5 If pH is higher/lower – it will affect the chemical reactions that take place Controlling the pH of cells is important for maintaining homeostasis