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Entry Task: Sept 10 th Monday This information does not count as an entry task question!! Sign off & Discuss Phys/Chem ws Discuss it Self Check on Phys/Chem.

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Presentation on theme: "Entry Task: Sept 10 th Monday This information does not count as an entry task question!! Sign off & Discuss Phys/Chem ws Discuss it Self Check on Phys/Chem."— Presentation transcript:

1 Entry Task: Sept 10 th Monday This information does not count as an entry task question!! Sign off & Discuss Phys/Chem ws Discuss it Self Check on Phys/Chem properties and changes.

2 Physical and Chemical Change Worksheet

3 True or False. If false, correct the underlined portion of the statement so that it is true. _____1. A physical change is a change of matter from one form to another without a change in chemical properties. _____2. A physical change is a change that occurs when a substance changes composition by forming one or more new substances. _____3. Color change is evidence that a chemical change may have occurred. _____4. Fizzing or foaming is evidence that a chemical change may have occurred. T CC PC T

4 True or False. If false, correct the underlined portion of the statement so that it is true. _____5. Production of light is evidence that a physical change may have occurred. _____6. Production of heat or light is evidence that a chemical change may have occurred. _____7. A change in odor is evidence that a physical change may have occurred. _____8. Chemical changes can be reversed by physical changes. CC T

5 Identify each of the following as either a Physical change (P) or a chemical change (C). 1.You cut your hair. _______ 2.Making a peanut, pretzel and cereal mixture. _______ 3.Baking soda reacts with vinegar and forms a gas. _______ 4.A piece of metal is bent in half. _______ 5.An aspirin is crushed into fine powder. _______ 6. Copper turns green when exposed to the environment. _______ 7.Two clear liquids are mixed and a yellow color forms. PC CC PC CC

6 Identify each of the following as either a Physical change (P) or a chemical change (C). 8.Baking cookies. _______ 9.Diamonds are used to scratch glass. _______ 10.A tree burns to form ashes. _______ 11.A piece of paper is crumpled up. _______ 12.Water freezes to form ice. _______ 13.Food spoiling. _______ 14.A candle burning. _______ 15.A candle melting. _______ CC PC CC PC CC PC

7 Analyzing Graphs The graph at the right plots the amount of light transmitted (% Transmittance) through a reaction flask as a function of time. Initially, the flask contains only air. After a short period of time, a light blue solution is added to the reaction flask. After another period of time, a clear solution is added to the flask, and the entire solution turns dark blue. Air only Light blue Clear Dark Blue

8 Analyzing Graphs 1. At what time is the light blue solution added to the reaction flask? Air only Light blue Clear Dark Blue ~2 minutes

9 Analyzing Graphs 2. At what time does the dark blue solution begin to form? Air only Light blue Clear Dark Blue ~7-8 minutes

10 Analyzing Graphs 3. The %Transmittance levels off at about 8 minutes. What is happening in the reaction flask? Air only Light blue Clear Dark Blue ~less than 25%

11 Analyzing Graphs 4. After 15 minutes, another solution is added to the reaction flask and the % Transmittance returns to 100%. Did another reaction take place? Please explain your answer. Air only Light blue Clear Dark Blue Yes, because the substance changed into another substance.

12 Analyzing Graphs 5. Two clear, colorless liquids are allowed to come to room temperature (22 °C). The timer is started and then the two solutions are mixed together to form another clear, colorless liquid. Looking at the graph to the right, at what time were the two solutions mixed together? Both solutions Start mix ~ 3 minutes

13 A Thought Experiment A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the glass above the solution, which has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining and both the solution and the droplets are clear and colorless. 6. Which of the following is not an indication that a chemical reaction has occurred? (a) formation of liquid droplets above the solution (b) the solution color changing from clear to yellow (c) the solution color changing from brown to clear (d) formation of a silvery metallic foil on the walls of the flask

14 A Thought Experiment A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the glass above the solution, which has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining and both the solution and the droplets are clear and colorless. 7. The formation of the silvery lining is an example of which of the following indicators of chemical change? (a) evolution of a gas (b) distinct color change (c) precipitate formation (d) temperature change

15 A Thought Experiment A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the glass above the solution, which has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining and both the solution and the droplets are clear and colorless. 8.(Short answer) There is only one reaction taking place in the flask. What is one possible reason for all of the color changes? 1.Condensation happened 2.Droplets Clear to yellow- reaction 3.The solution turned dark brown- could be same reaction just more reactants to deal with. 4.Eventually, all reactants will become a silvery product- just a very long time to happen

16 A Thought Experiment A sealed flask of a clear, colorless liquid is left sitting on an interior sunny windowsill. After about an hour, there are droplets of a clear liquid on the glass above the solution, which has turned yellow. After two hours, the solution is dark brown with clear, colorless droplets of liquid on the glass. After sitting on the windowsill for a week, the walls of the flask have a silvery lining and both the solution and the droplets are clear and colorless. 9.(Short answer) An observant chemistry student is enjoying a glass of iced tea during lunch (not in the lab!), and she notices that the color of her drink changes as the ice in the glass melts. Is a chemical reaction occurring? Why or why not? Melting ice is a physical change and causes her tea is becoming diluted with water.

17 Physical/Chemical Self Check

18 Identify the following as a chemical (C) or physical property (P): ______1. blue color ______2. density ______3. flammability (burns) ______4. solubility (dissolves) ______5. reacts with acid ______6. supports combustion ______7. sour taste P P C P C C P

19 Identify the following as a chemical (C) or physical property (P): ______8. melting point ______9. reacts with water ______10. hardness ______11. boiling point ______12. luster ______13. odor ______14. reacts with air P C P P P P C

20 Identify the following as physical (P) or chemical (C) changes. _____1. NaCl (Table Salt) dissolves in water. _____2. Ag (Silver) tarnishes. in water. _____3. An apple is cut. _____4. Heat changes H 2 O to steam.. _____5. Baking soda reacts to vinegar. _____6. Fe (Iron) rusts.. _____7. Alcohol evaporates. _____8. Ice melts. P C P P C C P P

21 Identify the following as physical (P) or chemical (C) changes. ______9. Milk sours. ______10. Sugar dissolves in water. ______11. Wood rots. ______12. Pancakes cook. ______13. Grass grows. ______14. A tire is inflated.. ______15. Food is digested. ______16. Paper towel absorbs water. C P C C C P C P

22 Part A Can you recognize the chemical and physical changes that happen all around us? If you change the way something looks, but haven’t made a new substance, a physical change (P) has occurred. If the substance has been changes into another substance, a chemical change (C) has occurred. 1. An ice cube is placed in the sun. Later there is a puddle of water. Later still the puddle is gone. 2. Two chemical are mixed together and a gas is produce. 3. A bicycle changes color as it rusts. 4. A solid is crushed to a powder. 5. Two substances are mixed and light is produced. P C C P C

23 6. A piece of ice melts and reacts with sodium. 7. Mixing salt and pepper. 8. Chocolate syrup is dissolved in milk. 9. A marshmallow is toasted over a campfire. 10. A marshmallow is cut in half. Part A Can you recognize the chemical and physical changes that happen all around us? If you change the way something looks, but haven’t made a new substance, a physical change (P) has occurred. If the substance has been changes into another substance, a chemical change (C) has occurred. C P P C P

24 Part B Read each scenario. Decide whether a physical or chemical change has occurred and give evidence for your decision. The first one has been done for you to use as an example. Scenario Physical or Chemical Change? Evidence… 1. Umm! A student removes a loaf of bread hot from the oven. The student cuts a slice off the loaf and spreads butter on it. Physical No change in substances. No unexpected color change, temperature change or gas given off. 2. Your friend decides to toast a piece of bread, but leaves it in the toaster too long. The bread is black and the kitchen if full of smoke. 3. You forgot to dry the bread knife when you washed it and reddish brown spots appeared on it. Chemical The bread is burned- changed into carbon and smoke released- odor change Chemical The knife changed colors- rust

25 Scenario Physical or Chemical Change? Evidence… 4.You blow dry your wet hair. 5. In baking biscuits and other quick breads, the baking powder reacts to release carbon dioxide bubbles. The carbon dioxide bubbles cause the dough to rise. 6. You take out your best silver spoons and notice that they are very dull and have some black spots. Physical Did not change your hair- evaporated the water Chemical Releasing of gases and changing to another substance Chemical The silver is tarnished- same thing as rusting changed colors

26 Scenario Physical or Chemical Change? Evidence… 7. A straight piece of wire is coiled to form a spring. 8. Food color is dropped into water to give it color. 9. Chewing food to break it down into smaller particles represents a _________ change, but the changing of starch into sugars by enzymes in the digestive system represents a ___________change. 10. In a fireworks show, the fireworks explode giving off heat and light. Physical Its still the same piece of wire- changed appearance Physical Its still water- just tinted Physical Breaking up food to smaller pieces Chemical Changing the food to something else Chemical Heat and light are released –changing into new substance

27 NEXT TIME- Math readiness- simple algebra 9 th grade Chemistry recollection This will separate the wheat from the chaff. STRONGLY recommend a calculator!


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