a) Exothermic. Heat is released by the charcoal.
b) Endothermic. Water absorbs heat from the surroundings, thus, evaporating.
c) Endothermic. Ice absorbs heat from the surroundings, thus, melting

Reactants need to have a higher energy than products, in other words, the bond strength of the products need to be higher ( stronger) than that of the reactants.

Temperature is the measurement of heat, in other words, temperature is just a number showing the direction of heat flow, but heat is a form of energy.
E.g. A thermometer tells you the temperature of an object, making it more tangible to understand . When melting an ice cube, heat is what causes it to melt and its temperature can be measured.

a) It contains 98% isoctane and 2% heptane. (The higher the rating, the lower the knocking)

b)It cannot be determined due to lack of information

a: Exothermic. Heat is released during combustion
b: Endothermic. Heat from the body allows water from the skin to change from liquid to gas and evaporate
c. Endothermic. Heat is absorbed from surrounding to melt the ice from solid to liquid

The bond energy of the products are larger than those of the reactants . This will lead to a large negative net energy indicating on an exothermic reaction. Hence, products should have a higher bond strength than reactants.

Heat is energy that that is transferred from one body to another as a result of a difference in temperature. In this case, when you touch a cup of coffee, what you feel is heat. On the other hand, temperature is a measure of hotness/ coldness expressed in terms of any scales like Celsius / Fahrenheit. Hence, if you use a thermometer to measure the hotness of the coffee, that is temperature.

a. 98% isooctane and 2% n-heptane
It has a higher octane rating than other blends sold at gasoline stations and hence is more resistant to knocking than these blends.

b. The octane rating provides no information about whether or not the fuel contains oxygenates. other labels around the pump should reveal this information.

a. Exothermic- potential energy in charcoal release as heat energy

b. Endothermic- Energy taken in to break the hydrogen bond of water to change from liquid to gaseous state

c. Endothermic-Energy taken in to break bond between molecules to change from solid to liquid state

To make a good explosion, the energy difference must be negative in value (exothermic)
The bigger the energy difference of the reaction, the more exothermic the reaction is. Hence to make a good explosion, relative bond strength of the product must be larger than those of the reactants which will lead to negative net energy change which is equal to a large exothermic reaction.

Heat refers to energy that flows from hotter to colder object. temperature determine the direction of heat flow.
Heat is the motion of energy and temperature is the measure of the speed of that energy.

a. Octane rating of 98 means that 98% isooctane and 2%heptane
b. No. Oxygenates are MTBE and ethanol. They have octane rating of over 100.

a) Exothermic – the charcoal burns the skin and gives out heat

b) Endothermic – the skin feels cooler when water (like sweat) evaporates from the skin

c) Endothermic – the ice takes in heat to become water, which is an endothermic process

The reactants should have very weak bonds and the products should have very strong bonds. The greater the energy difference between the products and reactants, the more vigorous the reaction as more energy is released.

Heat is the transfer of energy from a hotter object to a cooler object, while temperature is the absolute amount of energy possessed by the object.

For example, heat is the steam given off by a cooking pot, which can cook an egg, but temperature is a measurement of how hot the steam is.

a) An octane rating of 98 means that the gasoline has a knocking characteristic of 98% isooctane and 2% heptane. Isooctane has a lower boiling point than heptane and has a lower tendency to cause “knocking” in the engine. Therefore, gasoline with an octane rating of 98 would suggest a low tendency to cause knocking, and burns more smoothly.

b) The octane rating gives no clear indication of whether the fuel contains oxygenates. Examples of oxygenates include, MTBE, ETBE, methanol and ethanol. However, oxygenates enhance the octane number of the gasoline, assists combustion, reduces CO emissions and reduces knocking. Therefore, a high octane rating of 98 suggests that the gasoline does contain oxygenates, producing premium gasoline.

a. Exothermic. Heat is given out when coal briquette is burnt and used by people for heating up stuff, cooking food, used to power trains (heat to kinetic energy by heating moving wind that drives some turbine..) and also to keep people warm during cold weather.
b. Endothermic with respect to water molecules. It absorbs heat energy from our skin, hence we feel a cooling sensation
c. Endothermic. Solid to liquid transition involves absorbing energy to achieve a higher energy state of product (liquid state water).

For a good explosion, energy needs to be given out for it to be exothermic. Thus product’s energy needs to be lower than that of the reactants. Enthalpy change is determined by the equation delta H = bonds broken (energy taken in) – bonds formation (energy given out). Thus the magnitude of bond formation is bigger than the magnitude of bond breaking. Hence we can conclude that the product bond strength is bigger than that of the reactant bond strength.

Coffee – as the coffee is chilled, heat is lost, hence temperature also drops.
Heat – total energy of molecular motion, a process.
Temperature – measure of average heat/thermal energy of the molecules in a substance, known magnitude.
Another analogy would be temperature being the current score on the scoreboard of a soccer game, the heat being the goals scored. Temperature is like a measurement of heat just like how the scoreboard measures the amount of goals.
My friends are quite smart and all know Chemistry.

a. It is slightly higher than octane – 98% of isooctane and 2% of heptane. Hence slightly abit more prone to knocking.
b. It does not tell us anything about the availability of oxygenates. It may or may not contain. Even the word premium does not do anything to save it. The only is through determination of molecular compound composition through fractional distillation.

a. Exothermic – heat is released.
b. Endothermic – heat is absorbed and the skin cools down.
c. Endothermic – Drink is cooled.

Bond strengths of reactants are weaker than bond strengths of product. The bond strengths of reactants are weaker as bonds can break easily, thus absorbing less energy, while the bond strength of the products are stronger so a lot more energy is released during bond forming. Thus the reaction is highly exothermic.

Heat is a consequence of motion at the molecular level.
Temperature is the measure of an average speed of the motion.
Heat: Placing a cup of hot tea on the table and the hot tea becomes colder (transfer of heat to surroundings)
Temperature: When you cook food, the temperature increases.

a) Octane rating is a measure of a fuel’s ability to resist knocking. The higher the octane rating, the higher its resistance to knocking. An octane rating of 98 means a knocking characteristic of 98% isooctane and 2% heptane.

b) Yes. A high octane rating means that it is likely to contain oxygenates.

Endothermic: (b), (c) – Surrounding feels cooler as energy is absorbed.
Exothermic: (a) – Heat is produced and we can feel it.

Bond strength of products would be stronger than the bond strength of reactants such that the enthalpy change of combustion would be higher.

Temperature is a measurement, not a form of energy and thus cannot be transferred whereas heat is a form of energy that can be transferred. Heat is produced when water boils and we would need a thermometer to measure the temperature of the water.

(a) It is 98% isooctane and 2% hexane in terms of knocking characteristics, where isooctane is assigned a value of 100.
(b) The fuel does not contain oxygenates. Methanol, ethanol and MTBE contain oxygenates and have a value above 100. Hence, if a gasoline has an octane rating of 98, it should not contain oxygenates.

a) Exothermic as heat is released during the process of combustion. Overall change in enthalpy is negative as the energy of the products carbon dioxide and water are at a lower energy level than the reactants.
b) Endothermic as it takes in heat from its surroundings to change state from liquid to vapor.
c) Endothermic as it takes in heat from its surroundings to change state from soild to liquid.

For exothermic reactions, energy released in bond forming of products would be higher than energy absorbed in bond breaking of reactants. Therefore for a good explosion, the bond strength in reactants should be low so that less energy is absorbed for bond breaking and bond strength in products should be high so that more energy is released during bond formation.

Heat is an energy that is transferred from 1 body to another. Temperature is a measure of that heat energy (whether how hot or cold an object is).
For example. The temperature of 1 glass of boiling water and 1 teapot of boiling water are equal to each other. But they have different heat energy since they have different masses.
Another example is that temperature can be measured directly with a device called a thermometer but heat cannot be directly measured with a device. We need mass, temperature and specific heat capacity of the matter in order to obtain a result.

a) Gasoline with an octane rating of 98 has the same knocking characteristics as a mixture composed of 98% isooctane and 2% heptane. In essence, this is a blend that is resistant to knocking.
b) The octane rating does not give us any additional information about whether the fuel contains oxygenates or not. Other labels around the fuel pump should reveal the information.

a) Exothermic because it releases heat as it burns.
b)Endothermic. Because Particles gain energy as they go from a liquid to a gas.
c)Endothermic. Melting process needs heat to proceed and takes it from the warm water.

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

Heat is a form of energy. In contrast, temperature is a measurement
that indicates the direction heat will flow. Heat always flows from an object at high
temperature to an object at lower temperature. A drop of ot coffee is of the same temperature but you will get a bigger burn from the cup of coffee because of the higher heat content.

a)Gasoline with an octane rating of 98 has the same knocking characteristics as a mixture composed of 98% isooctane and 2% heptane. In essence, this is a blend that is resistant to knocking.
b)The octane rating does not give you any additional information about whether or not the fuel contains oxygenates. Other labels around the pump should reveal this information.