12/2 & 12/3 - 8th Grade Agenda

Learning Objective: Endothermic and Exothermic ReactionsCollect HW: Reading & Notetaking: p.111 – 113Science Fair Proposal PresentationsTextbook Reading p. 230-239HW: Reading & Notetaking p.114 – 116Reminder HW: Science Fair Background due 1/14 & 1/15 (10 Points)

Daily Reflection

• Prompt: Write 3 facts that you know about chemical changes

Which has stronger chemical bond – wood or glass?

• Windows in buildings hundreds of years old show no damage while wood frames have rotted away.

What are examples of Physical Change and Chemical Change?

• Physical Change: Ice to liquid. They are both H2O

• Chemical Change: Paper burning.

• Change in matter produces new substance.

Chemical Reactions What is a Precipitate?

• Precipitate: A solid that forms from solution during a chemical reaction

• Production of new materials that are chemically different from the starting materials.

What is Thermal Energy• Temperature is a measure of

the average mot______ of atoms

• Thermal energy is the total en_______ of all of the particles in the object

• Endothermic Change: Ice abs_________ thermal energy from its surroundings when it melts

• Exothermic Change: Warming you hands near a wood fire

ion

ergy

orbs

What is an Endothermic Reaction?

• Reaction that absorbs energy in the form of heat

Energy is absorbed by changing egg whites from a clear liquid into a white solid

What is an exothermic reaction?

• A reaction that release energy in the form of heat

Energy is released by burning airplane fuel

Endothermic & Exothermic Balloon Experiment

• Stretch the balloon fast on your forehead. What do you feel?

• Contract the balloon fast on your forehead. What do you feel?

Demonstration of Ions with Balloons

• Rub the inflated balloon fast on your hair.• Why does your hair stand up in the part of the

head where the balloon was rubbed?• Why does your hair doesn’t stand up in the part

of the head where the balloon was not rubbed?• Explanation: When you rub the balloon fast on

your forehead, you are moving electrons from your hair on to the balloon

Needle & Balloon Demonstration

• Rubber consists of long polymer chains that are folded and intertwined to form a network

• These factors allow rubber to be stretched and yet snap back to its original configuration

What is a Chemical Equation

• Reactant + Reactant Product + Product

• H2 + O2 H2O2

• Subscript shows the number of atoms of an element in a molecule

How many atoms are there?• Water: H2O• Carbon Dioxide:CO2

• Carbon Monoxide: CO• Methane: CH4

• Propane: C3H8

• Sugar: C12H22O11

• Rubbing alcohol: C3H8O• Ammonia: NH3

• Sodium chloride: NaCl• Washing soda: Na2CO3

• Baking soda: NaHCO3.