Unit 2: Physical Science Chemical Reactions

Transcription

1 Unit 2: Physical Science Chemical Reactions

2 Chemistry Chemistry is the branch of science that with the identification of the substances deals of which matter is composed Matter is anything that contains mass and has a volume. Mass is the amount of matter in a substance Volume is the amount of space a substance occupies

3 Common Chemical Reactions Oxidation of iron (rust Combustion of candle wax Vinegar (acetic acid) and baking soda (sodium bicarbonate)

4 WHMIS What does WHMIS stand for? Workplace Hazardous Materials Information System Why do we need WHMIS? WHMIS is a system of symbols that allows us to see clearly and quickly the potential dangers (hazards) that a chemical can cause. A chemical container may have one or several symbols on it.

5 WHMIS WHMIS Symbols

6 Material Safety Data Sheet The MSDS is intended to provide workers and emergency personnel with procedures for handling or working with that substance in a safe manner.

7 The MSDS includes information like: physical data (melting point, boiling point, flash point, etc.), toxicity health effects first aid reactivity storage disposal protective equipment spill handling procedures.

8 Chemicals Indentifying Unknown When performing chem labs there are several tests that can be performed to tell what products are released Oxygen gas: glowing splint. Place a glowing splint in a test tube. If the splint ignites then oxygen gas is present. Hydrogen gas: lit splint. If hydrogen gas is present, you will hear a pop and the splint will go out. Carbon dioxide: lime water. In the presence of carbon dioxide, clear colourless lime water becomes a milky substance.

9 Identifying Unknown Chemicals Water: cobalt chloride paper. Paper turns from blue to deep pink. Acid: litmus paper. Blue litmus turns red when acids are present. Base: litmus paper. Red litmus turns blue when bases are present (Bases Blue) Aqueous solution of salt: conductivity apparatus. If the solution conducts electricity it contains a salt (ionic compound).

10 Molecules and Molecular Formulas Molecules are compounds containing two or more non metal atoms (right of the staircase on the periodic table) Molecular Formula: chemical formula that shows the number and type of different atoms in a molecule Empirical Formula: simplest chemical formula that can be written for a compound (smallest whole number ratio of atoms) water H2O Molecular Formula H2O Empirical Formula hydrogen peroxide H2O2 Molecular Formula HO Empirical Formula dinitrogen tetrahydride N2H4 Molecular Formula NH2 Empirical Formula

11 Ions Ions are charged particles that have lost or gained electrons. Positively charged ions have lost electrons (lose negative charge, become positive) Negatively charged ions have gained electrons (gain negative charge, become negative) There are two types of ions: Simple ions are formed when atoms lose or gain electrons (Na +, H +, Cl, Al 3+ ) Complex ions are formed when compounds lose or gain electrons (CH 3 COO, NH 4 +, NO 3 ) Ions are made of formula units the way that compounds are made of atoms

12 Solutions Aqueous solutions are solutions where the solvent is water Electrolytic solutions are solutions that conduct electricity Nonelectrolytic solutions are solutions conduct that do not electricity

13 Physical Properties

14 Chemical Properties Chemical properties let us know how a substance can be used. For example, gold and platinum are made to use jewellery because they don t react easily with water or air. Trinitotoluene (TNT) is a favourite choice as an explosive because it remains relatively stable when exposed to shocks and vibrations, and does not react with water. There are 3 chemical properties:

15 Physical and Chemical Changes Physical changes are a change in the state of matter of a substance appearance or without changing it s chemical makeup E.g. When water boils it looks extremely different, but it s still H2O Chemical changes change the chemical makeup of a substance; after the change has taken place the atoms that make up the original compound have been rearranged.

16 Changes

17 Types of Compounds Ionic compounds involve the transfer of electron(s) resulting in ionic bonding made up of two oppositely charged ions (metal and nonmetal, or combination involving a complex ion) exist in the form of an ionic crystal lattice (not individual molecules) Binary molecular compounds involve the sharing of electrons resulting in covalent bonding (simple electron dot diagrams for diatomic molecules will illustrate this) composed of two nonmetals exist as individual molecules

18 Molecular Formulas First, how many of the first element are there? If there is more than one of the 1st element, write in the prefix for that number Second, name the first element in the compound. Repeat steps 1 and 2 for the second element, but this time use the mono prefix if there is only one of them. Change the end to ide. 1 mono 6 hexa 2 di 7 hepta 3 tri 8 octa 4 tetra 9 nona 5 penta 10 deca Then write the full name of the compound. For example, let s look at NO3. N is nitrogen. O is oxygen, but will be changed to oxide. There are 3 oxygen atoms, so the entire name of the molecule will be nitrogen trioxide. The formula tells you that in this molecule there is one nitrogen atom for every 3 oxygen atoms.

19 Trivial Names Some molecular formulas have trivial names instead of following the naming rules. You need to memorize these: H2O water H2O2 hydrogen peroxide NH3 ammonia C12H22O11 sucrose H2S hydrogen sulfide C6H12O6 glucose CH4 methane

20 Polyatomic Molecules Some non metal elements are commonly found as molecules in nature instead of single atoms. These are: Diatomic elements are: H 2, N 2, O 2, Halogens: F 2, Cl 2, Br 2, I 2 Other Polyatomics: Sulfur:S 8 Phosphorous: P 4 Use the name PF BrINClHOF (say Professor Brinkelhof) to help you remember, OR Please Help Our Needy Class Find Brains Immediately Sir.

21 Energy Level Diagrams Ions Remember from last year that energy level diagrams follow the 2e, 8e, 8e rule. For ions, the charge indicates how many electrons were lost or gained. Add or subtract this value from the number of protons to give you the number of electrons. Ions always have completely full energy levels.

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24 Ionic Compounds Naming ionic compounds is easier than molecular compounds, as you should remember from last year. For simple ionic compounds, you keep the first element name the same and change the end of the last element name to ide. E.g. Ca 3 P is calcium phosphide. For complex ionic compounds naming is easier. You just put in the metal name and the name of the complex ion (back of the periodic table). Most complex ions end in "ite" or "ate" E.g. NaHSO 4(s) is sodium hydrogen sulfate All ionic compounds are solid unless they are in solution

25 Determining the formula for Ionic Compounds To determine the formula for ionic compounds, we look at the ions that make up the compound: E.g. magnesium chloride (notice that there are NO CAPITAL LETTERS!) A magnesium ion is Mg 2+, a chloride ion is Cl - Now you have to switch the charges for each ion, and bring them down:

26 If you are finding the formula and the charges between the ions have a common factor, simplify the formula by diving by the lowest common factor: E.g. magnesium carbonate: Mg 2+ CO 3 2-

27 Multivalent Ions Some ions on the periodic table are known as multivalent ions. These ions have more than one possible charge. Their different charges are noted on the periodic table. These include titanium, iron, nickel, copper, platinum, tin, and gold. It is very important to know the difference between these two forms. We use roman numerals to distinguish between the two forms when naming them: A copper ion can have a charge of +1 or +2. For Cu +, the name is copper (I) ion. For Cu 2+ the name is copper (II) ion. Platinum can have a charge of +4 or +2. For Pt 2+ we say platinum (II) ion. For Pt 4+ we say platinum (IV) ion. Knowing which ion is present in a reaction is extremely important. Make sure you know which ion you re dealing with (look at your periodic table and the compounds produced by the given ions).

28 Finding Ionic Formulas Compound Name lithium phosphide potassium iodide copper (II) sulfate aluminum phosphate hydrogen acetate nickle (III) hydride niobium (V) dichromate gallium silicate silver nitrate iron (III) oxide Metal Ion Non-metal Ion or Complex Ion Formula

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