2. Whenever chemical reactions occur, energy is transferred to or from the surroundings. An exothermic reaction is one which transfers heat energy to the surroundings An e ndothermic reaction is one which takes heat energy from the surroundings

3. Exothermic process: a physical or chemical change that releases heat energy Burning fossil fuels is an exothermic reaction. reaction Exothermic Change - heat is given off and the temperature rises

4. Reactants  Products A + B  AB Forming a Chemical Bond - Releases Energy

5. EXOTHERMIC EXAMPLES A candle flame Rusting iron Burning sugar Glow sticks Fire crackers Some hand warmers Burning Wood Freezing Water

8. Endothermic process: a physical or chemical change that requires (or absorbs) heat energy Photosynthesis is an endothermic reaction (requires energy input from sun) reaction Endothermic reaction - heat is taken in and the temperature may drop

9. Reactants  Products AB  A + B Breaking a Chemical Bond - Absorbs Energy

10. ENDOTHERMIC EXAMPLES Baking bread Cooking an egg Photosynthesis Melting Ice Cold packs from nurse