The Chemistry of Life

1. The Chemistry of Life

2. Objectives (these are not officially IB) • What is matter? Compare its physical and chemical properties. • What are the phases of matter? • What is the structure of matter? • What are isotopes? • How is the periodic table arranged?

3. Properties of matter Matter: anything that occupies space & has mass. • Physical properties - can be observed & measured without changing the identity of the matter. • Mass: the quantity of matter. (Weight measures the force of gravity on an object) • Volume: the amount of space matter takes up. • Color, texture, taste, etc. • Melting point (temperature at which matter goes from a solid to a liquid) & boiling point (temperature at which it goes from a liquid to a gas) • Chemical properties - matter’s ability to change into something new as a result of chemical reactions.

4. Properties of matter Matter: anything that occupies space & has mass. Mass: a measure of the amount of matter that an object contains. • mass doesn’t change, but weight is a measure of an object’s attraction by gravity and varies with distance.

5. Phases of matter Phases of matter: different states of the same material (physical changes). • Solid, liquid, gas – the matter is the same, but in a new form. Ex: Ice, water, & steam are all H2O, but the atoms are in differ- ent alignments. Key words: freeze, melt, evaporate, dissolve, sublime, crack, mix.

6. Chemical elements All matter is made of elements: substances that cannot be broken down into other substances by chemical reactions. • 92 elements occur naturally; symbolized by 1 or 2 letters. Examples: • Carbon will only have carbon atoms. Carbon = C; • Oxygen = O (or O2); • Hydrogen = H (or H2); • Nitrogen = N (or N2); • Neon = Ne. But… • Gold = Au (Aurum); • Silver = Ag (Argentum); • Sodium = Na (Nasium) [words from Latin]

7. Chemical elements Atom: smallest unit of matter that retains the physical & chemical properties of the element; made of subatomic particles. Atomic Structure • Nucleus has 2 types of particles: Protons (+) positively charged. Neutrons (o) neutral (no) charge. • Outside the nucleus there is 1 type of particle: Electrons (-) negatively charged, in orbits. • The number of electrons equals the number of protons.

8. Chemical elements The number of electrons always equals the number of protons!

9. Chemical elements Every element has an atomic number & atomic mass. • Atomic number: equal to the number of protons, written as a subscript - 4Be . • All atoms of an element have the same atomic number.

10. Chemical elements Every element has an atomic number & atomic mass. • Atomic mass: equal to the number of protons + neutrons, written as a superscript - 9Be. • Deduce the number of neutrons by subtracting the number of protons from mass. • The number of neutrons can vary among isotopes of an element, but not the number of protons. • Mass is not the same as weight, which is an average of all isotopes. Ex. 1123Na pro. = ___; elec. = ___; neu. = ___ ?

11. Chemical elements Isotopes: atoms that have the same number of protons (& electrons) but different numbers of neutrons. • They react the same chemically. • Ex: Hydrogen – • 1H = protium • 2H = deuterium • 3H = tritium (for nuclear energy) • Radioactive isotopes: 12C → 14C used for radio- active dating of fossils.

12. Chemical elements Electron orbitals: electrons orbit the nucleus in shells. • Larger nuclei (more electrons) have more shells. • Physics determines the number in each shell. • 1st shell holds only 2 e-, 2nd holds a maximum of 8 e- • 3rd shell holds max. of 18 e-, 4th holds max. of 32 e- After Ar, the 3rd and 4th shells fill in a more com- plicated pattern.

13. Chemical elements

14. Chemical elements How are metals different from non-metals? • Metals are more malleable and ductile, as well as being good conductors of heat and electricity. • Nonmetals are brittle and act as insulators.

15. Chemical elements Noble gases do not react with other elements. Their outer electron shell contains a stable config- uration. The “Octet Rule” states that the outer shell needs to have 8 electrons for maximum stability. Helium’s only shell holds a maximum of 2.

16. The Chemistry of Life

17. Objectives • 3.1.0 – Compare physical and chemical reactions. • 3.1.1 - State that the most frequently occurring elements in living things are carbon, hydrogen, oxygen, and nitrogen. • 3.1.2 – State that a variety of other elements are needed by living organisms, in- cluding sulfur, calcium, phosphorus, iron and sodium. • 3.1.3.- State one role for each of the elements mentioned in 3.1.2.

18. Chemical reactions Chemical reaction: a process of chemical change. A chemical is changed into something completely different. • This is NOT freezing, melting, boiling, evaporation, which are physical changes. • It is burning, digestion, rusting: a complete change. • A chemical bond is made or broken. • Electron shells strive for stability. • The outer shell needs 8 electrons. (the octet rule)

19. Chemical reactions Chemical bonds: the type of force holding ions together. • Ionic bond: transfers electrons between atoms • Ex: Na + Cl → NaCl • Ion: an atom that gains or loses 1 or more electrons and, thus, has a charge: Na+, Cl-, Mg++

20. Chemical reactions Chemical bonds: the type of force holding ions together. • Covalent bond: shares electrons among atoms. • Ex: hydrogen & oxygen gas in the air; water - (H2O). Note the inner shell electrons of oxygen are hidden and do not participate in chemical reactions.

21. Chemical reactions Chemical bonds: the type of force holding ions together. • Bonding is determined by the number of electrons in the outer shell only; inner shells are hidden. • So elements within a column of the periodic table react similarly: H2O, Li2O, Na2O, H2S; BeCl2, MgCl2. Oxygen has 6 e- in its outer shell and needs 2 e- from 2 H, or 2 Li, or 2 Na to fill it’s outer shell with 8 e-, (a perfect #).

22. Chemical reactions Do not confuse chemical and physical reactions! • Physical reactions are more easily reversible and generally involve changes in temperature or breakage. • Key words: freeze, melt, evaporate, dissolve, sublime, crack, mix. • Chemical reactions change the material into something entirely different. It is the process of making and breaking chemical bonds. • Key words: rust, corrode, oxidize, reduce.

23. Chemical compounds Elements that exist in combinations (not purely one type of element) are called compounds. • Compound: a pure substance composed of 2 or more elements in a fixed ratio with emergent properties different from those of its combined elements. Examples: • NaCl = sodium chloride • SiO2 = silicon dioxide • Molecule: the smallest part of a compound that retains all of its properties. • (As an atom is the smallest part of an element that retains all of its properties.)

24. Chemical elements in the human body ~25 elements are essential to life: • Top 12: CHOPKINS CaFe Mg (Chopkin’s café, mighty good) Roughly 99 percent of your body's mass is composed of just six elements: • oxygen (65 percent); • carbon (18 percent); • hydrogen (10 percent); • nitrogen (3 percent); • calcium (1.5 percent); and • phosphorus (1 percent).

25. Chemical elements in the human body The most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen, and nitrogen. Protein DNA

26. Chemical elements in the human body The remaining 1 percent of the human recipe con-sists of tiny amounts of potassium, sulfur, sodium, chlorine and magnesium, plus even smaller traces of trace elements like iron, zinc, copper, iodine, & molybdenum (found in enzymes). • There are ~ 7x1027 atoms in a human body.

27. Chemical elements in the human body Five elements to know especially: • Calcium (Ca) – Essential to formation of bones and teeth, effective transmission of nerve impulses, and muscle contractions. • Sulfur (S) – Integral component of protein. • Phosphorus (P) – Essential to virtually every body process, including cell growth, bone and tooth formation, kidney function, and heart contractions; found in DNA. • Sodium (Na) – Helps balance pH in body, regulate water levels, and aid nerve conduction. • Iron (Fe) – Essential to general health and several body systems; serves as blood-oxygen transporter.