24
Endothermic Reactions
Subject: Chemistry
Sensor: Temperature
Aim:
To show the difference between a chemical or physical change and to also show a reaction has taken place.
Overview:
There are a few reactions in Chemistry where energy is absorbed from the surroundings during the reaction. When this happens, the temperature of
the reactants drops and an endothermic reaction has taken place. The experiment is also a simple rate of reaction experiment in that you can vary the
starting temperature of the water, size or shape of the antacid.
Equipment required:
LogIT Voyager
Temperature sensor
Small vessel, beaker or boiling tube
Antacid such as Alka-seltzer
®
(Sodium Bicarbonate and Citric Acid)
Water
Hazards:
If using warm water, make sure the water is not too hot for the ability of the pupils. Water
temperature above 55
o
C will scold children.
Care must be taken if using kettles to heat the water. Allow the temperature to cool before use.
Place the tubes over a tray to catch any spilt water.
Setup:
1. Connect the Temperature sensor to the datalogger.
2. You can use a clamp stand to hold the sensor if required.
3. Place the water into the small vessel, beaker or boiling tube.
Note: In the picture we have used a Micro Science kit with the Alka-Seltzer
®
about to be introduced to the water. This allows for the
use of small amounts of water and Alka-Seltzer
®
(2.0 ml of water and 0.3 g of Alka-Seltzer
®
in this example). You can use boiling tubes,
about 10ml of water and half a tablet which is about 1.5 g.
Be careful of using too much water as this will cause only a small drop in temperature due to the volume of water being reacted with the
tablet.
