Lake Nyos, Cameroon - Junior Science · Lake Nyos, Cameroon. Rev Jan 2015 Ms. Hennessey August 21st...
Transcript of Lake Nyos, Cameroon - Junior Science · Lake Nyos, Cameroon. Rev Jan 2015 Ms. Hennessey August 21st...
Rev A Feb 2007 Ms. Hennessey
One of the World’s Deadliest
Lake Nyos, Cameroon
Rev Jan 2015 Ms. Hennessey
August 21st 1986- Lake kills 1,700Carbon Dioxide gas killed all living things within a 15-mile (25km)
radius of the lake
Lesson Objectives
To be able to:
• List the physical and chemical properties of CO2
• Describe how to prepare CO2
• Explain the chemical reactions of CO2
• List the uses of CO2
Rev Jan 2015 Ms. Hennessey
Discovery of Carbon Dioxide
Scottish Chemist Joseph Black found that limestone (Calcium Carbonate) could be heated or treated with acids to yield a gas he called "fixed air."
He observed that the fixed air was denser than air and did not support either flame or animal life.
Carbon Dioxide Molecule - Structure
•Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms.
•It is often referred to by its formula CO2.
•The elements bond by sharing electrons.
C OODouble Covalent Bond
C
CO2
Double Covalent Bond
6P
6N O8P
8NO8P
8N
Oxygen
Carbon
Oxygen
Carbon Dioxide Molecule - Structure
The Preparation of CO2
•Carbon Dioxide is prepared by reacting dilute Hydrochloric Acid (HCl)
with Marble Chips Calcium Carbonate (CaCO3)
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
Rev A Feb 2009 Ms. Hennessey
Preparation of Carbon Dioxide
The Collection of CO2
Carbon Dioxide can be collected using two
methods
•by the upward displacement of air (its denser than air).
Or
•Downward displacement of water (it is only slightly soluble in water)
Physical Properties of CO2
Colourless, Odourless,
Tasteless Gas.
Denser (heavier) than air.
(Density is 1.5 times > air)
Slightly soluble in water
Does not support combustion.
It is an Acidic gas turning blue litmus red.
Turns limewater (Calcium Hydroxide – Ca(OH)2 milky white
It Dissolves in water to form an acid solution (Carbonic Acid – H2CO3)
Chemical Properties of CO2
Tests for Carbon Dioxide
Acidity Combustion Limewater
Turns BlueLitmus Red
Extinguishes a burning Candle
Turns Limewater Milky
Reactions of Carbon Dioxide
Lime water + Carbon Dioxide -> Chalk + water
Ca(OH)2 + CO2 -> CaCO3 + H2O
Water + Carbon Dioxide -> Carbonic Acid
H2O + CO2 -> H2CO3
• It is present in the Earth’s Atmosphere at a low concentration and acts as a Greenhouse gas.
• In its SOLID state, it is called dry ice.
• It is a major component of the Carbon Cycle.
Carbon Dioxide
Photosynthesis
Internal Respiration
Burning
Carbon Cycle
Carbon dioxide in the Air
Green Plants
Internal Respiration
Decay
Animals
Dry Ice
•Solid CO2 is referred to as dry ice and has a number of advantages over common ice– Much colder and can obtain
a temperature of (-78oC)
– It does melt into a liquid by ‘sublimes’ changes from a solid to a gas.
Uses include: - Cooling foods during
transportation- Coolant in nuclear reactors- Special effects on stage.
Uses of Carbon Dioxide
•Photosynthesis – used by green plants to make food (glucose) which is stored in the plant as starch.
•Fire extinguishers
•Carbonation of soft drinks.
Summary
• Colourless, Odourless andTasteless Gas.
• Denser (heavier) than air. (Density is 1.5 times > air)
• Slightly soluble in water
• Important part of the Carbon cycle
• Key molecule in photosynthesis
• Does not support combustion.
• It is an Acidic gas turning blue litmus red.
• Turns limewater (Calcium Hydroxide – Ca(OH)2 milky white
• It Dissolves in water to form an acid solution (Carbonic Acid –
H2CO3)
Rev Jan 2015 Ms. Hennessey