Lesson 9 Reactions
Reactions that Produce Useful Substances
There are many household, commercial, and industrial processes that use chemical reactions to produce useful substances.
B9.2 Toasting marshmallows
There are an incredible number of chemical reactions that are essential to society. There are also many reactions that may not be essential, but certainly do improve the quality of your life. In this lesson, we will look at only a few examples.
One of the most fundamental chemical reactions utilized every day in your home is cooking. The original purpose of cooking was to kill pathogens to make food safe to eat. In addition, the variety of food that was consumed greatly increased once
cooking methods became wide spread. Cooking can also increase the flavour of food.
B9.3 Leaves in sunlight
Photosynthesis is an amazing process. Put simply, it is the key to life on Earth. It is a chemical reaction that converts simple substances—sunlight, carbon dioxide, and water—into food!
6CO2(g) + 6H2O(l) + sunlight → C6H12O6(s) + 6O2(g)
6CO2(g) + 6H2O(l) + sunlight → C6H12O6(s) + 6O2(g)
Digging Deeper
©CNRL
B9.4 The algae process
B9.4 The algae process
The Algae Project
Canada’s Oil Sands Innovation Alliance (COSIA) is working on creating a bioreactor that uses algae to convert carbon dioxide into biofuel and biomass products.
B9.5 Baking
Both baking soda and baking powder are used in baking to produce carbon dioxide gas that will cause baked goods to rise. The difference between these two ingredients is that baking soda is a pure substance that needs an added reactant, specifically,
an acid—such as vinegar, buttermilk, or yogurt—to activate it.
NaHCO3(s) + H+(aq)→ Na+(aq) + CO2(g) + H2O(l)
Baking powder, however, is a mixture of two substances—a dry base and a dry acid— so it just needs to be moistened in order to activate the reaction.
NaHCO3(aq) + KHC4H4O6(aq) → KNaC4H4O6(aq) + H2O(l) + CO2(g)
NaHCO3(s) + H+(aq)→ Na+(aq) + CO2(g) + H2O(l)
Baking powder, however, is a mixture of two substances—a dry base and a dry acid— so it just needs to be moistened in order to activate the reaction.
NaHCO3(aq) + KHC4H4O6(aq) → KNaC4H4O6(aq) + H2O(l) + CO2(g)
Hydrogen has a bright future as a source of energy. When it is burned to produce power, it has little to no negative impact on the environment, unlike power produced by burning fossil fuels. Hydrogen gas can be readily produced by splitting water into its elements: hydrogen and oxygen.
2H2O(l) + energy → 2H2(g) + O2(g)
On the down side, large amounts of electricity are needed to split water; so depending upon how that electricity is generated, hydrogen fuel may not be such a clean energy source. You will learn more about different energy sources in Unit C.
Digging Deeper
© Wikimedia Commons
B9.6 Testing for hydrogen gas
B9.6 Testing for hydrogen gas
The splitting of water creates two colourless, odourless gases. How can each of them be identified? There are diagnostic tests that are easy to perform to confirm the identity of a gas. Watch this video to learn what these diagnostic tests entail.
B9.7 Silicon computer chip
Refining silicon is very important, as it is essential for the production of microchips. Silicon is readily available as sand, SiO2, but it is tightly bound in that compound and thus sand needs to undergo a chemical reaction to liberate
pure silicon. Silicon used in computer chips needs to be 99.9999999% pure. One of the reactions used to purify silicon is as follows:
SiO2(s) + 2C(s) → Si(l) + 2CO(g)
SiO2(s) + 2C(s) → Si(l) + 2CO(g)
© Wikimedia Commons
B9.8 Haber-Bosch schematics
B9.8 Haber-Bosch schematics
Ammonia is an essential compound that is used as a fertilizer, as a precursor in the production of explosives, as a precursor in the manufacture of other industrial chemicals, as a cleaning agent, as a refrigerant, and for many other uses.
Historically, the main source of reactant chemicals used to produce ammonia came from mining nitrate deposits. But these deposits were in limited supply; a new source was needed. Could ammonia be produced in the lab using a simple formation reaction?
N2(g) + 3H2(g) → 2NH3(g)
An obvious source for the reactant nitrogen was the atmosphere, since the atmosphere is comprised of nearly 80% nitrogen gas. However, atmospheric N 2 is exceptionally stable and will not readily react. Converting N2 into ammonia posed a challenge for chemists. This challenge was solved by the work of German Chemists Fritz Haber and Carl Bosch. They created the Haber–Bosch process used to manufacture 160 million tonnes of ammonia annually.
Did You Know?
B9.9 Historical explosives
During World War I, the production of ammunitions required large amounts of nitrate. The Allies had access to large sodium nitrate deposits in Chile. Germany had no such resources, so the Haber–Bosch process proved essential to the German war effort. Synthetic ammonia from the Haber–Bosch process was used for the production of nitric acid, a precursor to the production of ammunition.
Read This
Please read pages 78 to 82 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on important examples of chemical changes.
Remember, if you have any questions or you do not understand something, ask your teacher! Practice Questions
Complete the following practice question to check your understanding of the concept you just learned. Make sure you write a complete answer to the practice
question in your notes. After you have checked your answer, make corrections to your response (where necessary) to study from.- Identify a chemical reaction that is occurring at this moment in close proximity to you.
Answers will vary; examples of chemical reactions that may be occurring around you are cellular respiration, photosynthesis (if there are any plants), combustion (if you have a furnace running), or a neutralization reaction (if you have eaten an antacid such as Tums). There are countless reactions that are occurring all around you. If you are in doubt as to whether or not the answer you came up with is appropriate, please contact your teacher.