(a) Exothermic: Heat is released. You can feel the heat.
(b) Endothermic. Liquid to gas. Energy is released to break the weak interactions like hydrogen bonding.
(c) Endothermic. Solid to liquid. Energy is released to break the weak interactions like hydrogen bonding.

The energy level of reactants is higher than the products formed, hence the reaction is exothermic. Exothermic reactions happen when heat is released.

Bond-forming is an endothermic reaction. While. bond breaking for bond breaking is exothermic. Since the latter is smaller than the former, there is a good explosion.

In addition, the rapid increase in the volume of gas the caused the good explosion.

Temperature is a measurement of heat. Temperature determines the direction of heat flow, while heat is energy that flows from a hotter to a colder object.

For example, boiling hot water is 100 degrees Celcius.

One glass of water and a bathtub full water has the same temperature, but the glass of water has lesser heat than the bathtub.

(a) Octane rating of 98 is considerably high. This means that it would less likely explode before the ignition sparks. Hence, this is for better for the engine, as it resists knocking.

(b) Cannot be determined.
The number indicates a ratio. The higher the number, the better behaved the ignition.
Does not indicate the oxygenate level.

A) exothermic, heat is being released when charcoal briquette burns.
B) endothermic, heat is absorbed to change water from liquid to gaseous state.
C) endothermic, heat is absorbed to change water from solid to liquid state.

In an exothermic reaction, delta H is negative. The sum of the relative bond strength of products is more than the sum of the relative bond strength of the reactants.
Chemical explosion occurs when a solid reactant forms a gaseous product. Therefore bond strength of reactant is very Low and that of the product is very high.

Heat is the energy that flows from a hotter object to a cooler object while temperature is a measure of the average speed of the heat flow from a hotter to a cooler object.
Example for heat: when you touch a hot pan, heat is felt by your hand which is cooler
Temperature: comparing a pan of 50 degrees celcius and 30, you will feel th heat of the 50 degrees C faster than that of 30 degrees C

A) it has a knocking characteristic of 98% isooctance and 2% heptane.

B) it is not possible to tell from the octane rating

(a) Exothermic. Combustion reaction releases heat

(b) Endothermic. Water in liquid state absorbs energy to break the hydrogen bonds between the water molecules to form water in gaseous state

(c) Endothermic. Heat is absorbed to break the hydrogen bonds between the water molecules in solid state to form liquid state water.

The reactants must have a much higher bond strength than its product so that the reaction will release a large amount of energy to cause a good explosion.

Heat is the total energy possessed by the molecules in a piece of matter while Temperature is the average kinetic energy of a single particle in a system per unit of space.

Take for example,
A small bottle of drinking water might have the same temperature as a large pot of water, but the pot of water has more heat compared to the small bottle of drinking water as the large pot of water has more water and hence more total thermal energy.

(a) It tells me that since gasoline has an octane rating of 98, it is very prone to knocking hence it will have higher efficiency to ignite the fuel.

(b) It tells me that the fuel contains quite a high amount of oxygenates.

A. Exothermic, Heat is irradiated B. Endothermic, Water absorbs heat to break the hydrogen bonding between water molecules from the skin to change from liquid to gaseous state C. Endothermic, Ice absorbs heat from the surrounding to change from solid to liquid state.

To have a chemical explosion, the ideal reactant would be solid and the ideal product would be gas. the relative bond strength in solid (reactant) would be very much higher than that of gas (product)

Heat is the energy that flows from a hotter to colder object while Temperature determines the energy direction of heat flow

A. It has a knocking characteristics of 98% iso-octane and 2% heptane B. No, the octane rating is only a ratio of knocking characteristic and does not indicate the type or amount of additives.

a. Exothermic. Combustion is an exothermic process, heat is released.
b. Endothermic. Heat energy is required to break some H-bonds for change of state from liquid to gas.
c. Endothermic. Heat energy is required to break some H-bonds to change from solid to liquid state.

Bond strength in reactants are weaker than that in products. Reactants undergo bond breaking which is endothermic (energy absorbed). Products undergo bond making which is exothermic (change in H < 0). As such, since net change in heat is negative (exothermic), bond strength of products are stronger.

Heat is the energy that flows from a hotter to a colder object. Temperature determines the direction of heat flow. Heat is a consequence of motion at the molecular level;
temperature is a measure of the average speed of that motion.

a. Octane number of 98 means a knocking characteristic of 98%
isooctane and 2% heptane. Knocking is premature ignition.
b. No, oxygenates are compounds which contain oxygen in their chemical structures, however, isooctane and heptanes are hydrocarbons.

a. Exothermic – heat is released from the burning of the charcoal briquette.

b. Endothermic – energy is absorbed by water molecules to form water vapour.

c. Endothermic – energy is absorbed by ice to break the bonds between water molecules to change its state from solid to liquid.

For exothermic reactions, the energy for bond forming must be greater than the energy for bond breaking. Therefore the reactants have a smaller bond strength so it absorbs less heat and the products have a larger bond strength so it produces more heat.

Heat is a type of energy and heat travels from warmer to colder regions. Temperature is a measure of heat energy. Like a cup of hot coffee which transfers heat to its cooler surroundings resulting in a drop of temperature.

a. Octane rating of 98 means a knocking characteristic of 98% isooctane and 2% heptane.

b. The octane rating does not tell us whether the fuel contain oxygenates.

A) Exothermic, energy is released in the burning process.
B) Endothermic, heat has to be absorbed in order for the water to evaporate (overcoming hydrogen bond) . The body cools as a results
C) Endothermic, heat has to be absorbed to overcome the intermolecular forces, the hydrogen bonding between water molecules.

For a good explosion, the relative bond strengths of products should be way stronger, so that more heat will be released upon formation. For a better explosion, gaseous reactants are more effective.

Heat of an object refers to the kinetic energy in the object. Temperature is a form of heat measurement. Heating of water can be a an example. As water heats up, the molecules gain more heat energy and move faster, this will be reflected with a rise in temperature.

A) it means a knocking characteristic of 98% isooctane and 2% of heptane. The octane rating is a measure of the ability of the gasoline to burn smoothly without knocking.
B) The rating does not indicate if the fuel contains oxygenates. Information on oxygenates can be found on the other labels.

a. Exothermic: combustion gives off heat
b. Endothermic:removes latent heat of evaporation from our skin and cools surface temperature (energy is used to change water from liquid to gaseous state)
c. Endothermic:Energy is absorbed to break Intermolecular forces of attraction.

Energy for bond forming is much greater than energy for bond breaking.
Bond energy of products are much higher than the bond energy of reactants.

Temperature is like a measurement. Heat is the total energy of molecular motion.
For example the temperature of a small cup of water may 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, thus it has more thermal energy.

a. There are low knocking characteristics – 98% isooctane, 2% heptane
b. It doesn’t tell us that it contains oxygenates.

A) exothermic, heat is being released when charcoal briquette burns.
B) endothermic, heat is absorbed to change water from liquid to gaseous state.
C) endothermic, heat is absorbed to change water from solid to liquid state.

In an exothermic reaction, delta H is negative. The sum of the relative bond strength of products is more than the sum of the relative bond strength of the reactants.
Chemical explosion occurs when a solid reactant forms a gaseous product. Therefore bond strength of reactant is very Low and that of the product is very high.

Heat is the energy that flows from a hotter object to a cooler object while temperature is a measure of the average speed of the heat flow from a hotter to a cooler object.
Example for heat: when you touch a hot pan, heat is felt by your hand which is cooler
Temperature: comparing a pan of 50 degrees celcius and 30, you will feel th heat of the 50 degrees C faster than that of 30 degrees C

A) it has a knocking characteristic of 98% isooctance and 2% heptane.

B)

A) Exothermic; Energy required to break bonds and heat is released from burning.
B) Endothermic; Heat is absorbed therefore the water evaporates.
C) Endothermic; Heat is absorbed to melt the ice.

DHrxn = S (enthalpy of bonds broken) – S (enthalpy of bonds formed)

According to the equation above, the products (i.e. bond formation) must have a higher bond strength than reactants (i.e. bond breaking) to produce a highly exothermic reaction as a higher bond strength would correlate to more energy required to break/form the bond.

Heat is a form of energy that flows from a hotter to colder object. It is the consequence of motion at the molecular level whereas temperature is a measure of the average speed of that motion.

To explain such phenomenon to a friend (i.e. assuming he/she does not have chemical knowledge), we will use a small cup and a big cup of hot water. A small cup of hot water might be at the same temperature as the big cup of water, however, the big cup of water contains more heat because it has a larger volume of water.

A) Knocking characteristics of 98% iso-octance and 2% heptane.
B) It cannot be determined from knocking characteristics whether a fuel contains oxygenates or not. Other tests have been developed to determine the amount of oxygenates in the fuel.