a. This is an example of an exothermic reaction. A charcoal briquette burning is an example of combustion which releases energy once the activation energy has been met. Combustion will then be spontaneous and keep reacting until the fuel source is depleted.

b. This is an example of an endothermic reaction. Particles take in energy in orer to break their intermolecular interactions so that they are able to reach a more disorderly state of matter.

c. This is an example of an endothermic reaction. Particles take in energy in orer to break their intermolecular interactions so that they are able to reach a more disorderly state of matter.

Bond strengths of reactants are significantly lower than that of the products. This is because bond breaking requires energy which would mean that if the bond strengths of the reactants were significantly higher instead energy might instead be consumed to break the bonds. If the bond strength of reactants are significantly lower than that of products a significant amount of energy would be released causing the explosion.

Heat is the type of energy that is being transferred from objects of higher temperature to objects of lower temperature when they get into contact with one another. On the otherh and, temperature is the measure of the heat present in an object/substance.

An example is placing ice into hot milo. Hot milo will eventually experience a drop in temperature as the heat energy is transferred from the hot milo to the ice. At the same time, ice experiences an increase in temperature which increases its rate of melting.

a. It means that the knocking characteristics of said premium gasoline is equivalent to the knocking characteristics of a mixture of 98% iso-octane and 2% heptane.

b. While it may be possible to determine presence of oxygenates via other methods, it is difficult to determine the amount of oxygenates present in the gasoline just by the octane rating. That being said the addition of oxygenates tends to increase the octane rating.

a. Exothermic. A charcoal briquette releases heat as it burns due to the bond formation.
b. Endothermic. Water absorbs the heat necessary for hydrogen bonding for evaporation from your skin, and thus, makes the skin feel cooler.
c. Endothermic. Ice absorbs the necessary heat from the environment to break the hydrogen bond in order to melt into a liquid.

For a good explosion to occur, it has to be an exothermic reaction. Hence, the bond strength of the products has to be much higher than that of the reactants. Thus, this would result in a higher negative net energy change, leading to a good explosion.
For instance in methane explosion:
CH4 +2O2 → CO2 + 2H2O
Given that the C-H bond: 416 kJ/mol; O=O bond: 498 kJ/mol; C=O bond: 803 kJ/mol; O-H bond: 467 kJ/mol. Hence, the bond formation energy (products) is much larger that the bond breaking energy (reactants).
Moreover, for a good explosion, the product would be in a gas state.

Temperature is not a form of energy as it measures the average speed of the direction of heat flow. Meanwhile, heat is a form of energy that transfers from hotter region to colder region.
For example, a cup of water has the same temperature as a tub of water. However, the tub of water contains more heat than the cup of water. This is because the tub of water has a larger volume, thus resulting in a higher heat content as compared to the cup of water.

The octane rating is the measure of the ability of gasoline to burn smoothly without knocking.
a. The octane rating of 98 means that the premium gasoline has a knocking characteristic of 98% isooctane and 2% heptane.
b. The presence of oxygenates in the premium gasoline cannot be determined from the octane rating. Other labels on the packaging should reveal this information.

A. Exothermic: Combustion reactions are exothermic.

B. Endothermic: Conversion from a liquid state to gaseous state requires the compound to take in energy from the skin so as to break the strong hydrogen bonds between the molecules in the liquid state.

C. Endothermic: Ice absorbs environmental heat to overcome the strong intermolecular bonds to liquefy.

Exothermic reactions release energy during the reaction. Therefore, the energy of the products will be lower than that of the reactants.

A good explosion happens vert fast and almost instantaneously, therefore the bond strength in the reactant have to be as low as possible so that it can be broken fast during the reaction. On the other hand, bond strength of the products have to be high in order to form stable products.

Heat of an object is the total energy of all the molecular motion inside that object. Temperature, on the other hand, is a measure of the average heat or thermal energy of the molecules in a substance.
Hence, in other words, temperature is the scale or the unit of measurement for heat, just like centimetres is a unit of measure for length. Therefore, you can only feel “heat” and not “temperature”.

A. An octane rating of 98 refers to the amount of octane there is in the petrol. The higher the octane rating, the less likely knocking will occur, because octane burns slower since it has longer-chained hydrocarbon and is more resistant to igniting prematurely.

B. Adding oxygenates increases the concentration of octane in the fuel, so presumedly a premium gasoline with an octane rating of 98 will have a higher concentration of oxygenates contained in the petrol mix.

a. exothermic reaction – charcoal gives off heat when burned.
b. endothermic reaction – water takes in heat to evaporate, from liquid to gaseous state.
c. endothermic reaction – ice absorbs heat to melt from solid to liquid state.

The bonds within the reactants are weak in a highly exothermic reaction while those within the products are strong. The energy needed to break the bonds within the reactants is small as less energy is needed to overcome weak bonds. This thus leads to negative net energy change.

Temperature – the average measure of heat energy with respect to movement of molecules. Temperature determines the direction of heat flow.
Heat – energy flowing from a hotter to colder object

eg. you can set the temperature of a room to hotter or colder.
when you touch a hot vessel, you can feel the heat.

a. As the octane reading is 98, it has the same knocking characteristics as a mixture that contains 98% octane, therefore it is more resistant to knocking than gasoline with lower octane reading.

b. The octane rating does not say anything about whether the fuel contains oxygenates. Other labels provide that information.

a) Exothermic. A charcoal briquette release heat as it burns, combustion.
b) Endothermic. Evaporation is an endothermic change because water gain energy as they changes from liquid to gas state.
c) Endothermic. Melting process needs heat to proceed.

The reactant has way higher energy than the product. At the end of the reaction, it gives off a lot of energy and that cause the explosion. The higher the relative bond strength the bigger the explosion.

Temperature determine the direction of the heat flow while heat is the energy that flows from a hotter to a colder objects.
Example: Temperature of a small cup of water might be the same as the temperature of a large tub of water, but the tub of water has more heat because it has more water and thus more total thermal energy.

a) Gasoline with an octane rating of 98 has the same knocking characteristic as a mixture composed of 98% isooctane and 2% heptane. In essence, this is a blend that is resistant to knocking.
Knocking: explosion caused by premature burning in the combustion chamber.

b) The octane rating does not give any additional information about whether or not the fuel contains oxygenates. Other labels around the pump should reveal this information.

a. Exothermic. A charcoal briquette releases heat as it burns due the bond formation.
b.Endothermic. Water absorbs the heat necessary to break the hydrogen bonding for evaporation from your skin, and thus, the skin feels cooler.
c. Endothermic. Ice absorbs the necessary heat from the environment to break the hydrogen bonds in order to melt into a liquid.

For a good explosion to occur, it has to be an exothermic reaction. Hence, the bond strength (bond energy) of the products has to be much higher than that of the reactants. Thus, this would result in a higher negative net energy change, leading to a good explosion.

For example in methane explosion:
CH4 + 2O2 -> CO2 + 2H2O
Given that C-H bond: 416 kJ/mol; O=O bond: 498 kJ/mol; C=O bond: 803 kJ/mol; O-H bond: 467 kJ/mol
Hence, the bond formation energy is much larger than the bond-breaking energy.

Moreover, for a good explosion, the product would be in a gas state.

Temperature is not a form of energy as it is a measure of the average speed of the direction of heat flow. Whereas, heat is a form of energy that transfers from hotter region to colder region.

For instance, a cup of water has the same temperature as a tub of water. However, the tub of water contains more heat than the cup of water due to the larger volume of water in a tub, which resulted in the higher heat content of the tub of water.

Octane rating is the measure of the ability of gasoline to burn smoothly without knocking.

a. The octane rating of 98 means that the premium gasoline has a knocking characteristic of 98% isooctane and 2% heptane.

b. The presence of oxygenates in the premium gasoline cannot be determined from the octane rating. Other labels on the packaging should reveal this information.

a. Exothermic. Burning involves combustion with oxygen, energy is released.

b. Endothermic. Water absorbs energy from the skin to break the hydrogen bonds and evaporate.

c. Endothermic. Ice absorbs energy from the surroundings to change from solid to liquid state
– Hydrogen bond breaking.

The bond energies of the products are larger than those of the reactants. This leads to a large negative net energy change indicating an exothermic reaction.

Heat is the total energy of all molecular motion inside an object. Temperature is the measure of the average heat or thermal energy of the molecules in a substance.
The human body produces heat to support life and keep you warm. The measurement of the heat produced is your body temperature.

a. Fairly resistant to engine knocking due to higher activation energy. Less likely to have uncontrolled ignition when compressed.

b. Not sure. Octane rating does not indicate if any additives were added. Will have to look deeper into the other properties of the fuel to determine if any other additives were added.

a. Exothermic. When charcoal is burnt, it feels warm and hence we can assume that heat is released.
b. Endothermic. When water evaporates from our skin, it feels cool because water absorbs heat from our skin to evaporate.
c.Endothermic. When ice melts, it changes to liquid form (water). In order for it to melt, it needs to take in heat from surroundings. Hence, the process is endothermic.

For a good explosion, the chemical explosion needs to release a lot of energy and hence, it is a highly exothermic reaction. The net bond strength is a very large negative number. Hence bond strengths of products must be much lower than bond strengths of reactants. Gases are able to produce high energy release due to fast variation in volume change.

Temperature: The number and type of energy.
Heat: Amount of energy measured in units.
E.g. Comparing a small cup of water with a big cup of water, both have the same temperature. However, the big cup of water has more energy due to a larger volume.

a. 98% isooctane and 2% n-heptane
b. Insufficient information is provided to deduce if the fuel contains oxygenates. Octane rating only gives info on quality of fuel.

a. Exothermic. Process requires a larger amount of energy to form bonds than to break bonds. Energy of Products is lower than that of reactants.

b. Endothermic. Process requires a larger amount of energy to break bonds than to form bonds. Energy of products is larger than the energy of reactants.

c. Endothermic. Process requires a larger amount of energy to break bonds than to form bonds. Energy of products is larger than the energy of reactants.

In the reactants, the total bond strength should be lower than that of the products. This is because lesser energy is needed to break all the bonds in the reactant than the energy needed to form all the bonds in the products. In this way, only can the reaction be exothermic. Furthermore, the product needs to be a gas in order for the volume to expand drastically during the explosion.

Heat is a form of energy transfer – energy that flows from a hotter to cooler object. Heat is a consequence of motion at the molecular level, while temperature is a measure of the average speed of that motion. Heat is what we can feel with our senses, whereas temperature is a more specific measure of how hot object is.

For example, a pot of boiling water has a temperature of 100 degree celsius while ice has a temperature of 0 degree celsius. However, ice contains more energy or heat compared to a pot of boiling water.

a. It tells us that it has a knocking characteristic of 98% iso-octane and 2% of heptane.

b. Oxygenates are compounds that assist in the combustion in engines and help reduce co-emission and reduce knocking. The octane rating can be increased in the presence of oxygenates however the octane rating itself does not tell us whether the fuel contains oxygenates.

a) Exothermic. Energy is released from the process in the form of heat as the charcoal burns.

b)Endothermic. Energy is absorbed during the process when it changes from liquid to gaseous state.

c) Endothermic. Energy is absorbed during the process when it changes from solid to liquid state.

The bond strengths of reactants should be weaker than that of the products. To have a good exploson, the reaction should be very exothermic. The difference in relative bond strengths in reactants and products should be significantly large and there should be an higher number of bonds in the reactants. In addition, the products needs to be a gas for the volume to expand during an explosion.

Temperature is the measurement of the “hotness”/”coldness”. For example, heat from the fire increases the temperature of water during boiling.
Heat is what you can feel/sense. Heat is what makes water boils.

a)Octane number of 98 means a knocking characteristic of 98% and 2% heptane. This would be that knocking occurs less often.

b)No. The octane rating does not tell whether the fuel contains oxygenates. Further checks with the supplier needs to be done to ascertain the presence of oxygenates.