Exothermic and Endothermic Reactions © Teachable . Some rights reserved. http://teachable.net/res.asp?r=1910

Chemical Reactions All chemical reactions involve bond breaking and bond forming. Energy is needed to break bonds and released when bonds are formed. Chemical reactions are accompanied by a change in energy, mainly in the form of heat. www.makemegenius.com Free Science Videos for Kids

Exothermic and Endothermic Reactions A reaction in which heat is given out is exothermic. A reaction in which heat is taken in is endothermic. www.makemegenius.com Free Science Videos for Kids

Cold and hot packs How do instant hot and cold packs work?

Hot pack Pressing the bottom , the diaphragm breaks. Calcium chloride dissolves in water and warms it. The beverage gets warm.

Exothermic process Hot pack Energy Heat flows into the surroundings from the system in an exothermic process. Energy Surroundings Hot pack Exothermic Process comes from the Chemical energy stored in the substances that are reacting (Reactants) Temperature rises

Cold pack Water and ammonium nitrate are kept in separate compartments. Pressing the wrapper, the ammonium nitrate dissolves in water and absorbs heat. The pack becomes cold. It is used to treat sports injuries.

Endothermic process Cold pack Energy Heat flows into the system from the surroundings in an endothermic process. Surroundings Cold pack Energy Temperature falls

Cold pack We will repeat the process in a beaker with ammonium nitrate ( 25 g NH4NO3) + water (25 ml) and a thermometer. We will record the initial temperature of the water and the temperature after the dissolution of the salt. Observation: a temperature drop of…….

Endothermic and exothermic reactions Step 1: Energy must be SUPPLIED to break chemical bonds: Step 2: Energy is RELEASED when new chemical bonds are made: A reaction is EXOTHERMIC if more energy is RELEASED than SUPPLIED. If more energy is SUPPLIED than is RELEASED then the reaction is ENDOTHERMIC © Teachable . Some rights reserved. http://teachable.net/res.asp?r=1910

Changes in State www.makemegenius.com Free Science Videos for Kids

What is a Fuel???? What do we do with all of these? Petrol We Burn Them!!!! What gets released when we Burn them?? Carbon Dioxide Petrol Gas tank Wood fires Coal Peat

Definition time!!! A fuel is a substance that will undergo a chemical reaction in which a large amount of useful energy is produced at a fast but controllable rate. So fuels are the substances that we use to produce heat and/or electricity, and to run engines and motors. Many fuels consist of compounds of carbon and hydrogen, which are known as hydrocarbons. When hydrocarbons burn in unlimited air, carbon dioxide and water are produced. A combustion reaction is when a compound is reacted with oxygen to produce carbon dioxide and water. Combustion is commonly called burning and is an exothermic reaction, which means heat is produced.

Combustion Equation fuel (hydrocarbon) + unlimited oxygen  carbon dioxide + water

Forming Na+ and Cl- ions from NaCl is an endothermic process Endothermic process: a change (e.g. a chemical reaction) that requires (or absorbs) heat. Forming Na+ and Cl- ions from NaCl is an endothermic process Photosynthesis is an endothermic reaction (requires energy input from sun) www.makemegenius.com Free Science Videos for Kids

Measuring Heat reaction Endothermic reaction, heat taken in & temperature of the substance drops

EXOTHERMIC & ENDOTHERMIC REACTIONS Exothermic process: a change (e.g. a chemical reaction) that releases heat. Burning fossil fuels is an exothermic reaction www.makemegenius.com Free Science Videos for Kids

Exothermic reaction, heat given off & temperature of substance rises. Heat Released reaction Exothermic reaction, heat given off & temperature of substance rises. www.makemegenius.com Free Science Videos for Kids

Some everyday Examples