Science Module 8th Grade

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TAKS Objective 3 – The student will demonstrate an understanding of the structures and properties of matter. Complex interactions occur between matter and energy.

TEKS 8.10 (C) The student knows that complex interactions occur between matter and energy. The student is expected to: identify and demonstrate that loss or gain of heat energy occurs during exothermic and endothermic chemical reactions.

Learning Objectives identify endothermic and exothermic reactions associated with chemical changes Explain the loss or gain of heat during chemical reactions Identify chemical and physical changes associated with endothermic and exothermic reactions

Heat- transfer of energy Background Heat- transfer of energy

Exothermic- heat energy EXITS the system - ex. Combustion, evaporation of water - surroundings usually feel warmer

2Na(s) + Cl2(g)  2NaCl(s) + energy Salt An example of an exothermic reaction is the mixture of sodium metal and chlorine gas which yields table salt. 2Na(s) + Cl2(g)  2NaCl(s) + energy

Endothermic- heat energy ENTERS the system - ex. Cold packs, melting ice - surroundings usually feel cooler

How do cold packs work? The outer pouch contains water. The inner pouch contains ammonium-nitrate. When you “pop” the inner pouch, the chemical reaction absorbs heat energy from the surroundings. This is an endothermic reaction. The temperature of the solution falls to about 35 F for 10 to 15 minutes.

sunlight + 6CO2(g) + 6H2O(l)  C6H12O6(aq) + 6O2(g) Photosynthesis During photosynthesis, plants absorb the energy from the sun to convert carbon dioxide and water into glucose and oxygen. sunlight + 6CO2(g) + 6H2O(l)  C6H12O6(aq) + 6O2(g)

Physical change- change in size, shape or state of matter

Chemical Reaction - process in which one or more substances are changed into others. Chemical reactions are accompanied by a loss or gain of energy.

Chemical reactions always produce heat True or False Chemical reactions always produce heat

Chemical reactions can release or absorb heat, but can also create light, sound or electricity!

Heat can be lost, destroyed True or False Heat can be lost, destroyed or just disappear

Law of Conservation of Energy Heat energy is transferred from one object to another, or is transferred to another form of energy, but never disappears. Law of Conservation of Energy

Color change is always a physical property True or False Color change is always a physical property

Color is a physical property. Color change can be the result of a chemical change.

ENGAGE Cold Packs Rubber Bands Glo-sticks

EXPLORE Hot or Not students explore endothermic and exothermic chemical reactions using baking soda and calcium chloride

EXPLAIN List 3 physical properties of matter. List 3 physical properties for: Calcium chloride Baking soda Phenol red solution

Describe what happens with baking soda and calcium chloride are mixed. Describe what happens with baking soda, calcium chloride and phenol red are mixed. What are evidences of chemical change?

Is this an endothermic or exothermic reaction? How do you know? Give three examples of exothermic reactions in everyday life.

ELABORATE Ice Ice Baby Baking soda and vinegar Is this endothermic or exothermic? How do you know? Give 3 examples of everyday endothermic reactions.

Ice Cream Are the changes physical or chemical? Is the ice cream endothermic or exothermic? How do you know? Is the ice/salt mix endothermic or exothermic? How do you know?

EVALUATION Complete Type of Change? Endo/Exo chart Complete graph analysis questions