UNIT 3 DENSITY STRUCTURE S AND ISOTOPES

Transcription

1 UNIT 3 DENSITY STRUCTURE S AND ISOTOPES

2 What is density and how to use it? A Brief History of Chemistry Structure of an Atom How to make Ions? What are Isotopes?

3 DENSITY Density: is the mass of a substance per unit volume, or how much it weighs per given volume UNITS are g/cm 3, g/ml, or g/l Intensive property Density = mass volume You must identify if you are using this equation opposed to dimensional analysis (write the equation out) Use the correct units for the equation

4 PROPER UNITS FOR DENSITY All masses must be in grams (g) If not in base unit convert all masses into the base unit of grams through dimensional analysis Volume must be in milliliters (ml) for liquids, cubic centimeters (cm 3 ) for solids, and Liters (L) for gases Use dimensional analysis to convert to desired units A milliliter (ml) and cubic centimeter (cm 3 ) are the same amount

5 DENSITY TRIANGLE There are three possible variable that you may have to solve fore in density problems When given 2 of them it makes it extremely easy to solve for the third When trying to figure out which form of the density equation to use: cover up what you are looking for and the 2 units left and the sign between them shows you how to solve for it.

6 EX 3-1: WHAT IS THE DENSITY OF AN OBJECT WITH A VOLUME OF 35.7 CM 3 AND WEIGHT OF 85 g? onus: Is this a solid, liquid, or not enough information to know?

7 EX 3-2: IF THE DENSITY OF GOLD 19.3 g/cm 3 WHAT IS THE VOLUME OF 200 g OF GOLD?

8 EX 3-3: THE DENSITY OF LIQUID MERCURY IS 13.6 g/ml. HOW MUCH WOULD 35 ml OF MERCURY WEIGH (IN GRAMS AND POUNDS)? Hint: 1 pound = grams

9 EX 3-4: AN EMPTY GRADUATED CYLINDER WEIGHS 26.5 g. WHEN IT IS FILLED WITH AN UNKNOWN LIQUID TO THE 45.8 ml MARK THE NEW WEIGHT OF BOTH THE GRADUATED CYLINDER AND THE UNKNOWN LIQUID IS 70 g. WHAT IS THE DENSITY OF THE UNKNOWN LIQUID? the differences in masses in your equation there should be a m1

10 EX 3-5: A RECTANGULAR SOLIDS HAS THE DIMENSIONS FOR 3.4 BY 1.2 BY1.7 AND WEIGHS 1,500Kg. WHAT IS THE DENSITY Hint:1 in 3 = 2.54 cm 3

11 DENSITY OF WATER Memorize the specific density of water!!!! 1.0 g/ml This means 1.0 gram of water has a volume of 1.0 ml and 1.0m ml of water weights 1.0 gram This is only true at one temperature: 3.98º C Substance that has a density less then water will float in it and ones with a heaver density will sink

12 EX 3-6: HOW MUCH DOES 500mL OF WATER WEIGH IN GRAMS? 1.0 L? Hint: Use density of water to figure this one out

13 EX 3-7: A CERTAIN SUBSTANCE HAS A MASS OF 3.2 kg AND A VOLUME OF 1.5 ft 3. IF IT DOESN'T REACT WITH THE WATER, WOULD YOU EXPECT IT TO FLOAT OR SINK? Hint: Remember to convert all units to appropriate units 1 ft 3 = 12 in 3 1 in 3 = 254 cm 3

14 SPECIFIC GRAVITY Specific Gravity: of a substance is the density of the substance compared to the density of a designated standard (water) If you divide the specific gravity to our standard s (water) density. You will get the same number as the specific gravity Specific Gravity is unitless and Density has units

15 EX 3-8: MILK HAS A SPECIFIC GRAVITY OF HOW MUCH WOULD 1 GALLON OF MILK WEIGH IN GRAMS AND POUNDS? Hint: Convert Volume First 1 gal = 4 qt 1 L = 1.06 qt then ml to L Use specific gravity in density equation 1 lb = 454 g

16 BRIEF HISTORY Democritus- an ancient Greek, 400 B.C. He hypothesisxed that matter could be subdivided again and again until ir reaches particles that cannot divide. Other words, he was the first to suggest the existences of the atom. John Dalton: first to develop and publish a theory about how atoms look and behave.

17 JOHN DALTON S ATOMIC THEORY 1. All elements are composed of small particles called atoms that are indivisible 2. All atoms of the same element are identical. (not true today because of Isotopes) 3. Atoms of different elements are different. 4. Atoms of different elements can combine with each other only in simple whole number ratios to form compounds 5. Chemical reactions occur when atoms are separated, joined or rearranged

18 ERNEST RUTHERFORD Gold Foil Experiment - the atom was mostly space and that all positive charges were located in a very small central nucleus The Rutherford Gold Foil experiment shot minute particles at a thin sheet of gold. It was found that a small percentage of the particles were deflected, while a majority passed through the sheet. This caused Rutherford to conclude that the mass of an atom was concentrated at its center along with its protons.

19 MORE HISTORY Niels Bohr- A Danish scientist who was the first to suggest the planetary model of the atom. Meaning the electrons orbited the nucleus like the planets orbit the sun. Max Planck- A German Physicist who expanded and modified Bohr s model. He theorized and proved with the quantum mechanical model that electrons do not actually orbit the nucleus but are found only in definite areas based on the amount of energy they have. This theory holds true today

20 ATOMS Atom- The smallest unit of matter that still retains the properties of an element Each element consist of a certain type of atom different from the atoms of any other element (every type of atom is different) Atoms make up all matter!

21 SUBATOMIC PARTICLES Atoms are made up of three types of particles containing a charge Protons (+) These are found in the nucleus it is much larger then an electron Electrons (-) These are found outside the nucleus in the what is called the electron cloud Neutrons (neutral) these are found in the nucleus it is the same size as a proton but no charge.

22 ELECTRONS Electrons orient themselves around atoms in different levels called Electron Shells The outer most shell is called the Valence Shell The electrons on the outermost layer Valence Shell are called Valence Electrons

23 SUBATOMIC PARTICLES Most atoms are neutrally charged # of Electrons = # of Protons Protons and Neutrons are packed densely in the middle or core of the atom this is called the Atomic Nucleus Electrons are located in the outer rings of the nucleus or

24 ATOMIC NUMBER AND MASS All atoms of the same element have the same number of protons in their nuclei Atomic Number - the number of protons that is unique to an element it can also represent the number of electrons in a neutral atom Atomic Mass - Average masses of all the isotopes of that particular element weighted by their percentage of abundance (the units are atomic mass units)

25 WHEN USING ATOMIC MASS IN EQUATIONS: Atomic Mass = (% isotope 1)(mass of #1) + (% isotope2)(mass of #2) + etc. Even though you are finding an average know that you do not divide by the number of isotopes. You must either change your percentage to a decimal before putting them into your equation

26 EX 3.9: NATURALLY OCCURRING CHLORINE IS 75.53% CHLORINE-35 AND 24.47% CHLORINE-37. WHAT IS THE AVERAGE ATOMIC MASS THAT SHOULD BE PLACED ON THE PERIODIC TABLE?

27 EX 3-10: WHAT ARE THE ATOMIC #, ATOMIC MASS, PROTON #, & ELECTRON #?

28 EX 3-11: WHAT ARE THE ATOMIC #, # OF PROTONS, AND # OF ELECTRONS FOR EACH OF THESE ELEMENTS? Nitrogen (N) Oxygen (O) Neon (Ne) Potassium (K)

29 EX 3-12: NAME THE NEUTRAL ELEMENTS WITH THIS MANY PROTONS:

30 CHARGED PARTICLES A non-neutral atom is called a charged particle. The particle can either be positively or negatively charged. With charged particle you can only gain and loose electrons If the particle is positively charged it has less electrons then protons and vise versa is you have a negatively charged particle When writhing out an element that is charge you wright out the element as you would normally would then out beside it as an exponent wright the charge of the particle with a (-) for negative charges and a (+) for positive charges Mg +2 C -1

31 EX 3-13: WHAT PARTICLE HAS A +2 CHARGE AND 12 PROTONS?

32 EX 3-14: WHAT PARTICLE HAS A -3 CHARGE AND 33 PROTONS? How many electrons are in this charged particle?

33 EX 3-15: WHAT PARTICLE HAS 50 PROTONS AND 48 ELECTRONS?

34 ISOTOPE All atoms of a given element have the same number of protons but some atoms have more neutrons then other atoms of the same element thus they have greater mass. These elements are called Isotopes 12 C 13 C A Radioactive Isotope is one in which the nucleus days spontaneously giving off particles and energy

35 TYPES OF BONDS Bonding is how 2 or more elements come together to form a compound Some bonds are stronger then others (ex: covalent bonds are much stronger then hydrogen bonds) 4 Types Covalent Bonds Ionic Bonds Hydrogen Bonds Van der Waals Interactions

36 STRONG VS. WEAK CHEMICAL BONDING Strong Bonds: Covalent Ionic Weak Bonds: Hydrogen Van der Walls Interactions

37 COVALENT BONDS Covalent Bonds happen when valence electrons are being shared between 2 atoms equally This is a very strong bond but the strength of the bonds are dictated by how many pairs of valence electrons are being shared Single bonds have one pair of valance electrons being shared Double bonds have 2 pairs of valance electrons being shared

38 IONIC BONDS Ionic bonds happen when there is unequal sharing of valance electrons Because of unequal sharing one atom becomes more negative while the other atom becomes more positive Ions- Charged atoms Cation is the positively charged ion Anion is the negatively charged ion Ionic bonding must have both an anion and cation

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40 HYDROGEN BONDING Hydrogen bonds- When an hydrogen atom is already bound to make a compound and it exerts an attraction on other elements or compounds These bonds are individually weak but can add up and make many strong bonds

41 VAN DER WAALS INTERACTIONS These are interactions between compounds and their charge orientations (opposites attract)

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