Chapter 8. Lesson 1 Chemical vs Physical change

Transcription

1 Chapter 8 Lesson 1 Chemical vs Physical change

2 Materials Needed Today Please take these materials out of your backpack. Pencil Hot Sync Monday 2/3/14 Answer the following questions in complete sentences on your hot sync.

3 chemical property chemical change dissolving

4 Ability to Change In a chemical change, the properties that give a substance its identity change. Properties of matter help identify objects. Properties are either physical or chemical. What properties do elements have?

5 Ability to Change (cont.) A chemical property is the ability or inability of a substance to combine with or change into one or more new substances.

6 Chemical Properties Examples of chemical properties include burning or rusting. Some substances do not react.

7 Physical Properties Physical properties can be observed without changing the substance.

8 Chemical and Physical Changes Chemical changes change one substance into another substance. Usually chemical changes cannot be easily reversed. Changing Pennies Property Changes

9 PENNY LAB Lab in your notes: Question: What will happen if we drop a penny into a solution of zinc, sodium hydroxide, and water? Hypothesis:

10 Penny Lab Experiment: Materials U.S. copper pennies dated 1982 or earlier Zinc, granular NaOH (3 Molar or so) Distilled Water Procedure 1.) Mix NaOH 3M and about1 gram Zinc in water, heat on hot plate (or stove) until steaming, in a ceramic dish. 2) Add Penny and let sit 5-10 minutes 3.) Remove after chemical reaction occurs. 4.) Dry off pennies and place them on a towel. 5.) Place them in a beaker of distilled water. 6.) Using tongs, heat them in Bunsen burner until chemical reaction takes place.

11 Penny Lab Results: Zinc reacted with sodium hydroxide When the penny was put into the solution the zinc attached to the copper penny coating it. When the penny was heated the outer layer of zinc combined with the copper to create Brass. Conclusion:

12 Forming New Substances All chemical changes produce substances that are different from the starting substances. A compound is decomposed into its elements. Two elements join to form a compound.

13 Physical Changes A physical change is a change in which the properties of a substance change but the identity of the substance remains the same. Dissolving is a process in which substances mix evenly with one another.

14 Net Release of Energy (cont.) 8.3 Energy and Chemical Change An exothermic process releases energy. The products in an exothermic reaction have less energy than the reactants.

15 Net Release of Energy (cont.) 8.3 Energy and Chemical Change An endothermic process absorbs energy. The products in an endothermic reaction have a higher energy than the reactants.

16 1. A 2. B 3. C 4. D Which is a chemical change? A boiling B burning C dissolving D melting 0% 0% 0% 0% A B C D

17 1. A 2. B 3. C 4. D Which is NOT a chemical change? A sodium metal and chlorine gas react to form salt B salt dissolving in water C paper burning D iron rusting 0% 0% 0% 0% A B C D

18 1. A 2. B 3. C 4. D Which is NOT a physical change? A melting B boiling C dissolving D burning 0% 0% 0% 0% A B C D

19 Materials Needed Today Please take these materials out of your backpack. Pencil Hot Sync Tuesday 2/4/14 Answer the following questions in complete sentences on your hot sync.