I Can… -Distinguish between a physical-chemical properties and changes. -Apply the law of conservation of mass to chemical reactions. -Distinguish between homogeneous and heterogeneous mixtures. -Compare and contrast compounds, elements, and atoms.
Substances Substances- are matter that has a uniform and UNCHANGING composition Example: Water- pure water- is uniform (same through out) and its composition will ALWAYS be H 2 O
Physical Properties Physical properties- are characteristics that can be observed or measured without changing the samples’ composition. colorodor boiling point melting point conduction density malleablephase- at room temperature luster solubility
Physical Properties What is the difference between extensive and intensive properties? Extensive properties are dependent upon the amount of substance that is there. Example- length, volume, shape Intensive properties are independent of the amount of substance present. Example- density, or melting point or boiling point
What are chemical properties? Chemical properties describes the ability of a substance to react with another substance. Ability to catch on fire (flammability) Ability to rust (corrosion) Ability to burn skin (acid)
States of Matter Shapevolume Particle distance Solids Liquids Gases Definite Very close together Undefined- shape of container Defined Particles slide past each other Undefined- shape of container Undefined- Volume Compressible Particles are very very far apart
Physical Change When the appearance changes but not the composition of the substance remains the same is called a physical change. Water is still water whether it’s a solid (ice) or gas (steam) Hair is hair whether its long or cut short Example: Freezing, cutting, crumpling, breaking, crushing and boiling
Chemical Changes A process that involves one or more substances changing into new substances is called a chemical change. Examples- rusting car, burning paper, rotting food, tarnish. 4Fe (solid)+2 O 2 (gas) 4FeO (rust)
How do you know if it’s going through a chemical change? When observing a “change” at least 2 of these have to be present. Temperature change Presence of a gas (bubbles) Color change Odor change Precipitate- solid floaters
Law of Conservation of mass That mass is neither created nor destroyed during a chemical reaction- it is conserved
Law of Conservation of mass A chemical change results in a new substance being formed. They rearrange to form a new substance. What happens to the individual atoms during a chemical change? Hydrogen molecule – H 2 + Oxygen molecule – O 2 2 molecule of H 2 O- water
6. From a laboratory process designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was originally involved in the process? If 10 grams of hydrogen and 79.4 grams of oxygen are collected, that means there is 89.4 grams of water to start.
7. A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted? How many grams of sodium reacted? 39.7 grams of sodium chloride was obtained. 15.6 of it was sodium so that makes 24.1 grams of chlorine was used. 15.6 grams of sodium.
8. In a flask, 10.3 g of aluminum reacted with 100.0 g of liquid bromine to form aluminum bromide. After the reaction, no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of bromine reacted? How many grams of compound were formed? 10.3 g aluminum + (100g – 8.5 g= 91.5g) bromine = 101.8 grams of aluminum bromide
9. A 10.0-g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted? 10 g of magnesium – 16.6 grams of magnesium oxide = 6.6 g of oxygen
By composition. What its made out of Matter is sorted… Mixtures AND Substances What are the two broad categories of separating matter?
Spices Provide at least 5 examples. blood brass Dirt Pizza
A mixture is a combination of two or more substances in which each of the substances retain their identity. They can be separated by physical means. What are mixtures?
Define heterogeneous mixture. A mixture that is NOT evenly distributed. These types of mixtures have two or more compositions and are called heterogeneous mixture. Two kinds of Mixtures These mixtures can be separated by physical means. It can be very obvious-like a salad or difficult to catch- orange juice (pulp).
Define homogeneous mixture. A mixture that IS evenly distributed. Homogeneous mixtures are composed of one composition. These mixtures can be separated by physical means. What are some types of solutions? Homogeneous mixtures are the same composition through out the mixture. Solutions ARE homogeneous mixtures.
Matter MixturesSubstances Heterogeneous Homogeneous-(Solutions) Not the same through out Same through out physical Chemical
What are compounds? Are types of pure matter that can be broken down into simpler substances. What are elements? Are types of pure matter that can not be broken down into simpler substances. Sodium Chloride Elements are the simplest form of matter.
Matter MixturesSubstances Heterogeneous Homogeneous-(Solutions) Not the same through out Same through out physical Fixed composition/properties CompoundsElements H 2 O H 2 O 2 CO 2 Chemical Can be broken downCan’t be broken down H2O2CH2O2C
C 12 H 22 O 11 Sugar Examples of Substances Au gold NaCl Salt C 3 H 7 OH Alcohol CO 2 Dry Ice Cl Chlorine I Iodine O Oxygen H 2 O Water Na Sodium S Sulfur
C 12 H 22 O 11 Sugar Sort the substances Au gold NaCl Salt C 3 H 7 OH Alcohol CO 2 Dry Ice Cl Chlorine I Iodine O Oxygen H 2 O Water Na Sodium S Sulfur ElementsCompounds
Define Law of definite proportions- Law of multiple proportions Regardless of the amount, a compound is always composed of the same elements in the same proportion by mass. H 2 O- 2 grams come from hydrogen and 16 grams of oxygen. Basically- that different compounds CAN be made of the same elements but in different proportions. H 2 O 2 and H 2 O
I CAN… Trace the history of the discovery atom and the theories behind it. Explain the relationship between proton, electron and neutrons with atomic number and atomic mass. Define an isotope and explain why atomic masses are not whole numbers
Background on the Atom Greek philosophers organized matter into combinations of 4 fundamental elements and how each changes into one another:
Summarize Democritus’s ideas about the atom Matter composed of empty space in which atoms moved. Atoms were solid, homogeneous and indestructible, and indivisible. Different kinds of atoms have different sizes and shapes. Differing properties of matter were due to the size, shape and movement of atoms. Apparent changes in matter were a result of groups of atoms not changes in the atoms themselves.
Summarize Dalton’s ideas about the atom. All matter is made up of atoms. All atoms in a given element are identical, having same size, mass and chemical properties- different from atom of other elements Atoms cannot be created, divided into smaller parts, or destroyed. Different atoms combine in simple whole number ratios to form compounds In a chemical reaction, atoms are separated, combined, or rearranged.
Define atom The smallest particle of an element that retains the properties of the element is called an atom
In the 1800’s most scientist believed that the atom as a teeny tiny solid sphere that was not made of anything smaller
What is a cathode? It’s the negative terminal of a battery. What is a anode? It’s the positive terminal of a battery.
What is a cathode ray? A Cathode ray is a vacuum tube that had a positive end (anode) and a negative end (cathode) in which particle from the cathode traveled to the anode end creating a flash of light
Variations to the cathode ray Because the cathode ray is deflected towards the positively charged plate by an electric field, the particles in the ray must have a negative charge.
By the end of the 1800’s, what were scientists fairly convinced of? Cathode rays were actually a stream of particles The particles carried a negative charge. (The exact value of the negative charge was not known, however.)
Summarize J.J. Thomson’s experiment that leads to the discovery of the electron. Tried to determine the mass of 1 particle in the cathode beam. Determined the mass-charge ratio Found that his particle had a much lower ratio than hydrogen- the lightest known atom. This means there are particles smaller than an atom. Daltons theory is wrong- atoms are divisible.
Summarize Millikan’s experiment. Determined the exact charge to mass ratio of an electron He found that a single electron has a mass of an electron is 9.1 X10 -28th the mass of hydrogen. This means that it would take 1840 electrons to have the mass of 1 atom of hydrogen.
Evidence for models of the atom Atoms are made of negative particles Since our world is neutral (electrically) there HAS to be a complementary positive particle to balance this out. The positive particle has not been discovered yet so what does the atom “look” like”. Plum Pudding model.
Summarize Rutherford’s experiment. Aimed a beam of alpha particles at a thin layer of gold foil and zinc sulfide detector behind it would detect the particles path as is went through the foil.
Summarize Rutherford’s experiment. Expected minor deflections by the tiny electrons and because the positive charge was uniform in the atom that would not cause any deflections either.
Describe Rutherford’s nuclear model of the atom. Result: mostly no deflections and some major deflections occurred. Atom is mostly empty space and there is a dense region in the middle (nucleus) which contained all the positive charge for an atom and most of the mass
Define proton. It’s a subatomic particle carrying a charge equal to but opposite that of an electron; that is, a proton has a positive charge of 1+. Define neutron. It has a mass equal to a proton but carries no electrical charge- neutral.
Define Atomic Number Is the number of protons in the nucleus. What is the atomic number the same as? Atomic # = # of protons = # of electrons
What are isotopes? Atoms with the same number of protons but differ in the number of neutrons are isotopes
Define Mass Number Is the sum of the number of protons + neutrons in the nucleus of an atom.
What is the difference between atomic mass units and atomic mass? The atomic mass is the sum of the masses of particles. Atomic mass units is a calculated mass relative to the mass of particles in a carbon atom. 1 amu is 1/12 th the mass of a carbon atom.