Name: Class Period: Due Date: Unit 2 What are we made of? Unit 2.2 Test Review

Transcription

1 Name: Class Period: Due Date: TEKS covered: Unit 2 What are we made of? Unit 2.2 Test Review 8.5D recognize that chemical formulas are used to identify substances and determine the number of atoms of each element in chemical formulas containing substances 8.5F recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation of mass 8.5E investigate how evidence of chemical reactions indicate that new substances with different properties are formed 7.6A identify that organic compounds contain carbon, hydrogen, oxygen, phosphorus, nitrogen or sulfur 7.6B distinguish between physical and chemical changes in matter Answer the following questions: 1. Above is the chemical equation for photosynthesis. a. Circle the coefficients. b. Put a square around the subscripts. c. How many elements are involved in the equation for photosynthesis? d. What are the elements involved in the equation for photosynthesis? e. What are the compounds involved in the equation for photosynthesis? f. How many atoms of are there in 6H 2? g. What are the reactants in the equation for photosynthesis? h. What are the products in the equation for photosynthesis? 2. What does the Law of Conservation of Mass state?

2 3. How does the Law of Conservation of Mass impact the balancing of chemical equations? 4. Explain what is happening with the mass and matter in a chemical equation. 5. Write if each equation demonstrates or does not demonstrate the Conservation of Mass. Then explain why is does or does not demonstrate it. Reaction 1 Sn 2 + H 2 Sn + 2H 2 Demonstrates or Does not Demonstrate Why? 2 NH 3 + HCl NH 4 Cl 3 2Rb + P Rb 3 P 4 2C + 2S 2 CS 2 + 2H 2 6. In this chemical formula, 7H 2 SP 3 a. Which element has the greatest number of atoms? b. What is the number of atoms it has? 7. List each elements, and how many of each in the substance 7H 2 SP 3 *Don t know how to do this? Check out this video:

3 8. Complete the chart below. In the Evidence: How do you know column, explain how you know that the equation is a balanced or not balanced one. Equation 2NaH + H 2 C 3 Na 2 C 3 + H 2 Balanced or Not Balanced Evidence: How do you know? N 2 + H 2 NH 3 4FeS Fe S 2 3Fe + 4H 2 Fe H 2 Pa H H H 9. Write the chemical formula for the substance above. 10. Draw a model of H 2 2 and 2H in the table below. Model Atom Count H = = H = = Are they, H 2 2 and 2H, the same substance?

4 Explain your answer: 11. Label the diagram with the names of each part or step: Na Na 12. What do subscripts in chemical formulas tell you? 13. What do coefficients in chemical formulas tell you? 14. What are the main six indicators/evidence that a chemical reaction has occurred? 15. Explain why a color change when two or more substances are mixed together, does not always indicate a chemical change. 16. In a chemical reaction, what happens to the elements?

5 17. A chemical change produces a new whose properties are compared to the properties of the reactants. 18. Some students conducted an investigation in which they added four different solid substances to separate beakers of water. They stirred the mixtures for one minute and then recorded their answers in this data table: Which substance most likely caused a new substance to be formed when mixed with water? Explain why you chose your substance. 19. How many atoms are represented in this formula? Write your answer on the blank. P 4 S 3 = 20. What is an endothermic reaction? 21. What is an exothermic reaction? 22. Look at the graphs. Explain what each graph is representing and how the lines show energy changes. Endothermic: Exothermic:

6 23. A student mixes two unknown substances together and observes what happens. What evidence is shown that a chemical reaction may have occurred? 24. How do you know that when iron is exposed to air, the result is a chemical reaction? 25. Which equation shows that the total mass during a chemical reaction stays the same? Circle the correct one. 2Na + 2H 2 0 NaH + H 2 H H 2 Mg + Cl 2 MgCl In a chemical reaction, the elements and numbers of each atom remain the same. If this true, what must also be true about the mass (grams)? 27. What elements are in an organic compound? 28. What are physical properties? 29. List at least 5 physical properties 30. Explain why a state of matter change is NT evidence of a chemical reaction.

7 Study Tips and Reminders 1. Complete this test review and then study! 2. Text book pages that relate to this material: Unit 3 p and (second half of Unit 3 in the textbook relates to the second half of our unit) 3. Notes are always posted on the website look in Unit Remember, the Unit Enrichment and Review section at the bottom of every unit has even more videos and links. 5. The labs and their concepts turn into questions on the test! Take a look at the chemical reactions lab and notice evidences that a chemical reaction has occurred. 6. Main concepts: Know how read a chemical formula what do the subscripts and coefficients mean? How can you tell which elements are present. Know the Law of Conservation of Mass and how it is applied to chemical reactions Know what makes a compound organic or not Know the difference between physical and chemical properties and changes Exothermic and endothermic reactions Know how to recognize what a balanced equation looks like