KS3+Endothermic+and+exothermic+reactions

Explore and explain the idea of endothermic processes and exothermic reactions. A reaction can give off heat or take in heat depending on whether chemical bonds are broken or formed. Chemical reactions that take in energy are called endothermic reactions. During photosynthesis, plants take in energy from the Sun and use it to synthesises food. Photosynthesis is an endothermic reaction. Reactions thaat produce heat and give off energy are called exothermic reactions. Elplosions are dynamic exothermic reactions. They happen when an exothermic reaction quickly produces huge amounts of gases that have nowhere to escape. Combustion or burning is always an exothermic reaction. It gives off energy and heat. Article taken from GRAPHIC LIBRARY 'The dynamic world of chemical reactions with MaxAxiom'. www.raintreepublishers.co.uk
 * Exothermic and Endothermic Reactions **

Exothermic reaction(Combustion): Heat is __ given out .__ It feels hot due to heat being released from the reaction. Endothermic reaction: Heat is __ taken in .__ It feels cool due to heat being taken from our body.

When you dissolve //ammonium nitrate// in water then the temperature of the reaction mixture falls. The temperature falls because heat energy is taken in by the reaction mixture. The heat energy is taken from the surroundings. Dissolving ammonium nitrate in water is an example of an [|endothermic reaction].

AIM : To find out if the reaction has an increase or decrease in temperature

Tasks/Procedure 1. Add about 3-4 cm of water into the test tube, measure the temperature of water. Then add two spatulas of ammonium nitrate, shake a bit and measure temperature again.

2. Add about 2 cm depth of acid into the test tube, measure the temperature. Then add an equal volume of alkali and shake a bit, check the temperature.

3. Add about 3-4 cm of water into the test tube, measure the temperature of water. Then add two spatulas of anhydrous copper sulphate, shake a bit and measure the temperature again. THE SPATULA MUST BE DRY!!

4. Place a 2 cm depth of acid into a test tube. Measure the temperature. Then add a small piece of Mg and put your thumb on the mouth of the test tube to collect the gas.( What gas is it? Hydrogen gas.) When you feel pressure of the gas on your thumb, test with a lighted splint. MAKE SURE TO PUT OFF THE SPLINT IN THE SAND BOX. As soon as you finish task 4, check the temperature again.

DATA TABLE: (Include columns for temperature change & observations) at start || Temperature at the end || A. Exothermic or B. Endothermic || Ammonium nitrate ||  ||   ||   || sodium hydroxide ||  ||   ||   || anhydrous copper sulphate ||  ||   ||   || magnesium ||  ||   ||   ||
 * Task || R e a c t a n t s || Temperature
 * 1 || Water,
 * 2 || hydrochloric acid,
 * 3 || water,
 * 4 || hydrochloric acid,

CONCLUSION: If there is rise/increase in temperature after a reaction, it is called __exothermic . __ If there is drop/decrease in temperature after a reaction, it is called __endothermic . __ From above experiment, tasks __2,3,4, __<span style="font-family: 'Lucida Console',Monaco,monospace;"> are exothermic. Task __<span style="color: #ffffff; font-family: 'Lucida Console',Monaco,monospace;">1 __<span style="font-family: 'Lucida Console',Monaco,monospace;"> is endothermic.

<span style="font-family: 'Lucida Console',Monaco,monospace;">Examples of __<span style="color: #ffffff; font-family: 'Lucida Console',Monaco,monospace;">endothermic __<span style="font-family: 'Lucida Console',Monaco,monospace;"> process(physical change) are melting and boiling. Examples of __<span style="color: #ffffff; font-family: 'Lucida Console',Monaco,monospace;">exothermic __<span style="font-family: 'Lucida Console',Monaco,monospace;"> process(physical process) are freezing and condensation.