Chemistry Test Review

Your test will be: 30 Multiple Choice 2 Open Ended Questions 1 Griddable

Hints for doing well on this test: Read each question carefully Answer the question you are asked Re-read each answer Make sure you have answered the question completely Make sure your answer relates to the question

Example Questions And how to answer them

One of your friends stays overnight at your house One of your friends stays overnight at your house. The next morning, your mother cooks him some fried eggs for breakfast. He says, "I don't like fried eggs, can you change them to poached eggs instead?" – Use what you know about physical and chemical changes to explain why it is NOT possible to change the fried eggs to poached eggs.

You MUST discuss changes & why in your answer It is not possible to change the fried eggs into poached eggs because cooking eggs is a chemical change Chemical changes produce new products that are very difficult to reverse Answer identifies cooking an egg as a chemical change Answer describes chemical changes as being difficult to reverse because the original substance is changed into a new substance

Scientists used to think electrons moved in orbits around the nucleus. How do scientists currently describe the movement of electrons?

Notice the word movement – the question is not asking about location only Electrons move in an electron cloud around the outside of the nucleus The electrons do not follow a particular path

Is O2 a compound? Explain your answer. Oxygen gas normally exists as O2 molecules. Each molecule contains two oxygen atoms. Is O2 a compound? Explain your answer.

Make sure you EXPLAIN No [answer] A compound must contain atoms from more than one element [explanation]

Why is the state of matter a physical property and not a chemical property?

You must know the meaning of each of these terms to answer this question State of matter Physical property Chemical property

Sometimes giving an example helps explain your thinking: Changing state does not change the identity of the matter. Chemical properties can't be observed without changing the substance. Water is still water whether it is ice, liquid, or vapor. [example]

Vanadium, with an atomic number of 23, and bromine, with an atomic number of 35, are both in the same period as germanium. – Explain why bromine is most likely a non-metal. – Explain why vanadium is most likely a metal.

Vanadium is most likely a metal because it on the left side of the same period Bromine is most likely a non-metal because it is to on right side of the same period.

The operating system and programs that run on a computer depend on tiny electrical circuit boards called chips, which are made of materials called semi-conductors. Based on the label "semi-conductor," which type of element would you predict is used to make computer chips? Explain.

“Semi-Conductors” Metalloids because their ability to conduct electricity lies somewhere between the good metallic conductors and the poor nonmetallic conductors.

In the fall, you rake leaves into a pile, burn them, and spread the ashes back on the lawn as fertilizer. What are the chemical changes and what are the physical changes in this process?

Think about each part of the question Raking the leaves into a pile and spreading the ashes are physical changes. Burning the leaves and the ashes being broken down by the lawn for fertilizer are chemical changes.

Define the law of conservation of mass and explain how it relates to physical and chemical changes.

2 Parts to this question Definition: Explanation: The law of conservation of mass states that mass cannot be created or destroyed. Explanation: This means that the mass of any substances present before a physical or chemical change is equal to the mass of the substances present after the change.

What are the three types of reactions?

The Three types of Reactions are: Synthesis: Two molecules come together to form a compound Decomposition: A compound breaks down into its separate parts Replacement: One element switches places with another element.

What is evidence that a chemical reaction took place?

Chemical Reaction Evidence that a chemical reaction took place are: Color Change Temperature Change Formation of a Precipitate Gas Production

What is important to know about the periodic table?

The Periodic Table Basics The periodic table is arranged by increasing ATOMIC mass. Columns or groups are VERTICAL and the elements in the same group HAVE SIMILAR PROPERTITES. Rows/period on the periodic table tell the number of electron shell an element has. Group 1 is the Alkali Metals, group 2 is the alkaline earth metals, Group 17 is the Halogens and group 18 is the Noble Gases.

Metals, Non-Metals, Metalloids Metals (to the left of the zig zag line) MOST ELEMENTS ARE METALS! Shiny, ductile, malleable, good conductors of thermal energy, solid at room temperature, reactive with oxygen, reactive with acids Nonmetals (to the right of the zig zag line) Not shiny, poor conductors, not ductile, not malleable, some are reactive with other substances, some are not Metalloids (On zig zag line, B, Si, Ge, As, Sb, Te, Po, At) Have properties of both metals and nonmetals, less malleable and more brittle than metals, solid at room temperature, some are good semiconductors, most react with oxygen, some react with water or acids

Compare an element, atom, and compound.

An ELEMENT is identified by the CAPITAL LETTERS. Example H, O, P. A COMPOUND is one or more element bonded together, CO2 ATOMS are identified by the subscript in a compound: H2O HYDROGEN- 2 OXYGEN- 1

What happens to the ENERGY in a phase change?

KNOW THIS CHART as iquid OLID Boling Point Condensation Melting Point Freezing OLID

How are New Elements, Ions, Isotopes formed?

New elements are formed any time the PROTONS are changed because it changed the ATOMIC NUMBER. Ions are formed when the electrons change and it causes the element to either be POSITIVELY or NEGATIVELY charged. Isotopes are formed when the NEUTRONS change and it causes the MASS of the atom to change and NOTHING else!