Endothermic and exothermic reactions Flashcards
What is an endothermic reaction
When energy is taken in and temperature decreases
What is an exothermic reaction
When energy is given out and temperature increases
What are examples of exothermic reactions
Combustion, respiration, rusting
What is combustion
Combustion is the chemical reaction between a fuel and oxygen
What is a fuel
Fuel is a substance that gives off heat when it reacts with oxygen
What are some examples of fuels
coal, oil, natural gas, petrol, wood
What are the three things you need to start and maintain a fire
Fuel, oxygen and heat
What is the equation of complete combustion
hydrocarbon + oxygen -> carbon dioxide + water
What is the equation of incomplete combustion
hydrocarbon + oxygen -> carbon monoxide + water
Why is carbon monoxide toxic
because it bind to the hemoglobin in red blood cells so oxygen cannot bind
Why is carbon monoxide dangerous
Because it is odorless and colorless so one does not realize that they are exposed to it.
What apparatus will you need to investigate the products of combustion
a burning source (a candle), a funnel, a suction pipe, cobalt chloride paper, lime water and test tubes
How do you know if water is a product of combustion
If water is present then the cobalt chloride paper turn from blue to pink
How do you know if carbon dioxide is a product of combustion
If carbon dioxide is present then the lime water would turn cloudy
What are some factors to consider of having a good fuel
the energy released, the pollution it causes, its cost and its availability
What metals rust
Iron and steel rust
What is needed for rusting
Water and oxygen
What ways could you identify that these two substances are needed for rusting
To have three iron nails and place them in three different tubes. One tube should have the nail with water and is exposed to oxygen. Another tube should have a nail with boiled water since it has no oxygen and a layer of oil on top of it because it prevents oxygen to diffuse. The last tube should have a nail with calcium chloride inside because it absorbs water vapor and it should be exposed to oxygen.
What will the results be for the investigation of rusting
The tube where the nail is placed in water and exposed to oxygen will rust and the rest will not.
What can you do to delay rusting
you can paint, galvanize or add oil onto the metal
What is oxidation
When a substance burns in air it reacts with oxygen and the oxygen combines with elements in the substance to form a compound
How is rusting an example of oxidation
The oxygen dissolves in the water and reacts with the metal to form iron oxide.
What is the equation for rusting
iron + oxygen + water –> hydrated iron oxide
What is respiration
The process in which energy is released from food
What is aerobic cellular respiration
When the food substance called glucose reacts with oxygen
What is the equation for aerobic cellular respiration
glucose + oxygen–> carbon dioxide + water
What are some examples of endothermic reactions
Melting, evaporation, cooking, production of lime by thermal decomposition of limestone, photosynthesis
How is melting an endothermic physical reaction
Once the temperature of the surroundings rise above 0 degrees, ice absorbs heat energy energy from the air and starts to melt. It is also reversable
How is evaporation an endothermic physical reaction
the liquid molecules must absorb heat in order to transform into gas molecules. It is also reversable.
How is cooking an endothermic chemical reaction
heat energy they take in allows chemical reactions to take place in which change their structure and taste.
How is sherbet an endothermic chemical reaction
when you eat sherbet the heat in your body is taken in and your mouth feels cool and this is because when it dissolves in your mouth the two chemicals react together
What is the equation of sherbet
citric acid + sodium hydrogen carbonate–> sodium citrate + carbon dioxide + water
How is photosynthesis an endothermic chemical reaction
Plants do not release energy as they make food- they take energy in from sunlight
What is the photosynthesis equation
carbon dioxide + water–> glucose + oxygen
How is Thermal decomposition of limestone an endothermic chemical reaction
When limestone is heated it breaks down to form calcium oxide and carbon dioxide. Limestone take in the heat from the burners and is decomposed
what is the equation of the thermal decomposition of limestone
calcium carbonate–> calcium oxide + carbon dioxide
