00:01
Hello students, in this question we have been given some chemical reactions and we have to tell which one is endothermic and which one is exothermic.
00:08
So our first reaction is combustion of hydrogen gas.
00:19
Now the chemical reaction for combustion of hydrogen gas is this.
00:24
Excess hydrogen is combusted in the presence of limited supply of oxygen to give water molecules.
00:32
Now the balanced chemical equation for this reaction will be like this.
00:36
So this is how it is formed.
00:40
Now when combustion reaction happens, heat energy is always released.
00:46
Net heat is produced.
00:47
That is why combustion will be an exothermic reaction.
00:54
Now let's look at our second reaction.
00:56
Second reaction is photosynthesis.
01:02
So in photosynthesis reaction, sunlight that means energy from sun is absorbed and since net energy is getting absorbed, this reaction will be of endothermic nature.
01:23
Now let's look at our third chemical reaction.
01:26
Third is evaporation of water.
01:35
So a bucket contains water which is getting evaporated.
01:39
Now when the amount of water is evaporated to the environment, we know that the molecules of water that are evaporated are in gaseous state.
01:52
That means they have higher energy.
01:55
Therefore, that is the reason why cooling is observed after evaporation.
02:02
That means water molecules are taking away some amount of energy from the solution or we can say the liquid.
02:10
That is why evaporation is also a type of exothermic reaction.
02:18
Now let's look at our fourth reaction.
02:20
Our fourth reaction is cooking hot dogs on fry pan.
02:30
Now we know that cooking involves heating the contents.
02:37
Whether they are hot dog or any type of cooking involves consumption of heat energy.
02:41
That is why cooking is also a type of endothermic reaction because heat is getting consumed while cooking.
02:51
Now fifth reaction is burning of coal.
02:58
So when coal is burnt in presence of oxygen, it produces co2 and heat.
03:06
So heat is getting produced from the combustion of coal or we can say burning of coal.
03:12
That is why this is also a type of exothermic reaction.
03:18
Now let's look at our sixth chemical reaction...