TAKS REVIEW CHEMISTRY

Scientific Method

Using Data Tables

THE ATOM For any element: Number of Protons = Atomic Number Number of Electrons = Number of Protons = Atomic Number Number of Neutrons = Mass Number - Atomic Number

KRYPTON For krypton: Number of Protons = Atomic Number = 36 Number of Electrons = Number of Protons = Atomic Number = 36 Number of Neutrons = Mass Number - Atomic Number = = 48

ISOTOPES Atomic number is the same, mass number is different Difference in mass is due to NEUTRONS Krypton-84: 36 protons, 48 neutrons Krypton-83: 36 protons, 47 neutrons

IONS Ions: atom loses or gains ELECTRONS Metals: lose electron, become positive (Na + Ca 2+ Al 3+ ) Non-metals: gain electrons, become negative (F - O 2- N 3- ) Number of electrons lost or gained determined by position in periodic table

PROTONS STAY THE SAME IN IONS AND ISOTOPES (change number of protons, change the element)

Matter Anything that takes up space and has mass In reactions matter is conserved: cannot destroy or create matter (atoms) Just re-arrange the atoms

Matter Flowchart Non-uniformUniform Solutions

Mixtures

Bonding Ionic: Made up of ions (+ and -) Metal/non-metal Solid, crystal compounds Lattice structure Higher boiling/melting points

Ionic Bonding

Bonding Covalent Sharing of electrons Non metal/ non metal Gases, liquids (some solids) Lower boiling/melting points

Covalent Bonding

BONDING Both bonding types involve valence electrons Valence electrons determined by position on periodic table Atom wants configuration of noble gas elements (full outer shell of electrons)

Metallic bonding Electrons are shared by atoms in metals – account for properties of metals: conductivity, malleable, ductile

WATER Water has a covalent bond Electrons are not evenly shared, resulting in slight charge POLAR Compound (meaning uneven charge) Oxygen slightly negative, hydrogen slightly positive

WATER Hydrogen bonding occurs between water molecules Gives water unique properties –Good solvent (universal solvent) –Higher boiling temperature (when compared to other molecular compounds) –Solid is less dense than liquid (ice floats)

Water

pH Measure of hydronium concentration in water Measure for acid and bases

Properties of Matter Physical: can be observed or measured without changing the identity of the substance –Color –Density –Hardness –Melting/boiling points

Properties of Matter Chemical: ability of substance to undergo a change that transforms it into a different substance –Reacts with water –Explodes in air

Changes Physical: doesn’t change identity –Melting/freezing –Boiling/condensing –Dissolving –Pounding –evaporating

Changes Chemical: changes identity –Rust –Explode –Reacting Signs of chemical changes: –Bubbles, precipitate (solid forming), energy released or absorbed (heat or light)

Rock Cycle

Sample questions When a 10% hydrochloric acid solution is heated in an open test tube, the test tube should always be pointed — A so bubbles are visible B at a 180° angle from the flame C toward a ventilated area D away from nearby people ***

Sample questions 5 The picture shows a model of the element A fluorine B helium C beryllium D oxygen ***

Oxygen (O 2 ) is an example of — A an alloy B a molecule C a salt D a mixture *** Photosynthesis Light energy 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Respiration C 6 H 12 O 6 + 6O 2  energy + 6CO 2 +6H 2 O

To produce 4 molecules of sugar, a plant needs — F 6 molecules of hydrogen G 12 molecules of ATP H 18 molecules of water J 24 molecules of carbon dioxide *** Photosynthesis Light energy 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 Respiration C 6 H 12 O 6 + 6O 2  energy + 6CO 2 +6H 2 O

Which of the following will allow measurement of a liquid’s volume with the greatest precision? A 50 mL cylinder graduated in 1 mL increments B 100 mL cylinder graduated in 0.5 mL increments C 100 mL cylinder graduated in 1 mL increments D 200 mL cylinder graduated in 5 mL increments ***

Which of the following pieces of equipment would be most appropriate for measuring the volume of a marble? ****

In the rock cycle, which of these is a chemical change involved with the formation of igneous rocks? F Compression of sediments G Heat loss from lava H Subduction of plates J Formation of minerals ****

What characteristic of water remains the same no matter what is dissolved in it? A The ratio of hydrogen to oxygen B The ability to refract light C The hydroxide ion concentration D The freezing temperature ****

What are the coefficients that will balance this chemical equation? A 2, 1, 1 B 3, 4, 2 C 2, 2, 1 D 4, 3, 2 ****

Which of the following salts has the greatest solubility in water at 25°C? F CaCO 3 G FeS H HgCl 2 J KClO 4 **** Solubility Rules 1.All sodium, potassium, and ammonium salts are soluble. 2.All silver, lead, and mercury salts are insoluble. 3.All carbonates, sulfides and hydroxides are insoluble. 4.All sulfates are soluble except calcium sulfate and barium sulfate.

As temperature drops to the dew point, clouds form in the atmosphere, and dew forms on ground surfaces. A scientist proposes that adding more water molecules to the atmosphere will change the dew point. This proposal is — F an invalid observation G a valid hypothesis H an invalid problem J a valid conclusion ****

Laboratory equipment is cleaned and properly stored after use primarily so that — A chemical products can be measured and recorded as data B time is saved in setting up the next experiment C toxic materials can be kept in the laboratory D the possibility of contamination in the laboratory is minimized *****