Endothermic and exothermic reactions

Question 1

What is an endothermic reaction

Answer 1

When energy is taken in and temperature decreases

Question 2

What is an exothermic reaction

Answer 2

When energy is given out and temperature increases

Question 3

What are examples of exothermic reactions

Answer 3

Combustion, respiration, rusting

Question 4

What is combustion

Answer 4

Combustion is the chemical reaction between a fuel and oxygen

Question 5

What is a fuel

Answer 5

Fuel is a substance that gives off heat when it reacts with oxygen

Question 6

What are some examples of fuels

Answer 6

coal, oil, natural gas, petrol, wood

Question 7

What are the three things you need to start and maintain a fire

Answer 7

Fuel, oxygen and heat

Question 8

What is the equation of complete combustion

Answer 8

hydrocarbon + oxygen -> carbon dioxide + water

Question 9

What is the equation of incomplete combustion

Answer 9

hydrocarbon + oxygen -> carbon monoxide + water

Question 10

Why is carbon monoxide toxic

Answer 10

because it bind to the hemoglobin in red blood cells so oxygen cannot bind

Question 11

Why is carbon monoxide dangerous

Answer 11

Because it is odorless and colorless so one does not realize that they are exposed to it.

Question 12

What apparatus will you need to investigate the products of combustion

Answer 12

a burning source (a candle), a funnel, a suction pipe, cobalt chloride paper, lime water and test tubes

Question 13

How do you know if water is a product of combustion

Answer 13

If water is present then the cobalt chloride paper turn from blue to pink

Question 14

How do you know if carbon dioxide is a product of combustion

Answer 14

If carbon dioxide is present then the lime water would turn cloudy

Question 15

What are some factors to consider of having a good fuel

Answer 15

the energy released, the pollution it causes, its cost and its availability

Question 16

What metals rust

Answer 16

Iron and steel rust

Question 17

What is needed for rusting

Answer 17

Water and oxygen

Question 18

What ways could you identify that these two substances are needed for rusting

Answer 18

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.

Question 19

What will the results be for the investigation of rusting

Answer 19

The tube where the nail is placed in water and exposed to oxygen will rust and the rest will not.

Question 20

What can you do to delay rusting

Answer 20

you can paint, galvanize or add oil onto the metal

Question 21

What is oxidation

Answer 21

When a substance burns in air it reacts with oxygen and the oxygen combines with elements in the substance to form a compound

Question 22

How is rusting an example of oxidation

Answer 22

The oxygen dissolves in the water and reacts with the metal to form iron oxide.

Question 23

What is the equation for rusting

Answer 23

iron + oxygen + water –> hydrated iron oxide

Question 24

What is respiration

Answer 24

The process in which energy is released from food

Question 25

What is aerobic cellular respiration

Answer 25

When the food substance called glucose reacts with oxygen

Question 26

What is the equation for aerobic cellular respiration

Answer 26

glucose + oxygen–> carbon dioxide + water

Question 27

What are some examples of endothermic reactions

Answer 27

Melting, evaporation, cooking, production of lime by thermal decomposition of limestone, photosynthesis

Question 28

How is melting an endothermic physical reaction

Answer 28

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

Question 29

How is evaporation an endothermic physical reaction

Answer 29

the liquid molecules must absorb heat in order to transform into gas molecules. It is also reversable.

Question 30

How is cooking an endothermic chemical reaction

Answer 30

heat energy they take in allows chemical reactions to take place in which change their structure and taste.

Question 31

How is sherbet an endothermic chemical reaction

Answer 31

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

Question 32

What is the equation of sherbet

Answer 32

citric acid + sodium hydrogen carbonate–> sodium citrate + carbon dioxide + water

Question 33

How is photosynthesis an endothermic chemical reaction

Answer 33

Plants do not release energy as they make food- they take energy in from sunlight

Question 34

What is the photosynthesis equation

Answer 34

carbon dioxide + water–> glucose + oxygen

Question 35

How is Thermal decomposition of limestone an endothermic chemical reaction

Answer 35

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

Question 36

what is the equation of the thermal decomposition of limestone

Answer 36

calcium carbonate–> calcium oxide + carbon dioxide