Chemistry Test Review

1. Chemistry Test Review

2. Your test will be: • 10 short answer questions • Each question is worth 10 points each • Partial credit will be given

3. 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

4. Example Questions And how to answer them

5. 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.

6. 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 You MUST discuss changes & why in your answer

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

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

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

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

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

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

13. 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]

14. 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.

15. 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.

16. 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.

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

18. 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?

19. 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. Think about each part of the question

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

21. Definition: 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. 2 Parts to this question