1. Chemical Reactions Review
Answers to Study Guide

2. What is a physical change? Give 2 examples.
-no new substance is formed. Ex) phase changes, changing shape or size
2. What is a chemical change? Give 2 examples.
New substance forms. Ex) burning, bubbling, gas is produced
3. Which of the following are chemical changes?
Mixing a metal with an acid
d. Combining vinegar and baking soda
e. Burning wood in a campfire
4. List the 5 types of evidence that a chemical reaction has occurred.
Bubbles (gas), precipitate (solid), energy change, odor, color change
5. For the following reaction, underline the reactants and circle the products.
Reactants: AgNO3 + KCl
Products: AgCl + KNO3

3. 6. True or False: Doing something to increase the collisions between particles will cause the rate of the reaction to increase (reaction will occur faster). -True 7. Why does increasing the temperature of the reactants cause the reaction to occur faster? -increasing the temperature increases the amount of energy which makes the particles move faster which means that they will collide more often 8. Why does increasing the concentration of the reactants cause the reaction to occur faster? -more particles increases the changes of the particles colliding 9. Why does increasing the surface area of the reactants cause the reaction to occur faster? -more SA makes the reaction happen faster because there is more of the reaction exposed

4. 10. Why does adding a catalyst to the reactants cause the reaction to occur faster?
-a catalyst will lower the activation energy so there is less energy needed to start the reaction; therefore, the reaction speeds up
11. What does the Law of Conservation of Mass state?
-matter cannot be created or destroyed
12. How are exothermic and endothermic reactions different?
Exothermic—heat is released
Endothermic—heat is absorbed (feels cool to the touch)
13. Describe what happens in each of the 4 types of chemical reactions:
synthesis—2 reactants put together to make one product
Decomposition—1 reactant breaks down to make 2 products
Single replacement—one element replaces another
Double replacement—two elements replace each other

5. 14. How do you balance a chemical equation
14. How do you balance a chemical equation? You can add a coefficient but cannot add/change a subscript.
15. Balance the following equations and tell what kind of reaction it is:
2Al + 3NiBr2  2AlBr3 + 3Ni single replacement
S8 + 12O2  8SO3 synthesis
2HgO  2Hg + O2 decomposition
Zn + 2HCl  ZnCl2 + H2 single replacement
16. The substance that is formed in a reaction is called—product
17. When gasoline is burned, are new atoms formed or are new molecules formed?
-molecules
18. The substance that is changed in a reaction is called—reactant

6. 19. A chemical equation is balanced by adding or changing the – coefficient 20. In a balanced reaction, the total mass of the reactants is equal to the total mass of the—products 21. What is a short way to describe chemical reactions using formulas and other symbols? -chemical equation 22. Substances to the right of the arrow in a reaction are called— products 23. Substances to the left of the arrow in a reaction are called— reactants 24. Reactions that release energy are called—exothermic 25. Why would you add a catalyst to a chemical reaction? -to speed it up

7. 26. What kind of change is not actually a change in the particles themselves, but may be a change in the size, shape, or state of matter? -physical change 27. Energy being released is a sign of what? -chemical change 28. Why does food cook faster at a higher temperature? -the particles are moving faster 29. What happens to the atoms in a chemical reaction? They are rearranged 30. What says that matter is not created or destroyed, but is conserved? -Law of Conservation of Mass

8. 31. An insoluble solid compound that comes out of solution during a double replacement is a—precipitate 32. If there is no coefficient written, what does that mean? -the coefficient = A log burning is an example of what type of reaction? -chemical 34. What kind of change is dissolving? -physical