(a) Exothermic process. The heat that is released by the briquette can be felt in the surrounding.

(b) Endothermic process. The water molecules must take in heat energy (increase in kinetic energy) in order to evaporate. (The skin gets cooled as water evaporates).

(c) Endothermic process. The ice will take in heat energy from the warmer surrounding, causing the molecules to gain energy (eventually cause bond breaking).

Qn 2:

For an ‘ideal’ explosion, the relative bond strengths of the reactants must be weak while that of the products must be strong.

Bond breaking in reactants = endothermic = +ve

Bond formation in products = exothermic = -ve

In order to produce a very -ve reaction (a good explosion), the bond breaking value must be low while the bond formation value must be high. (small positive + large negative = negative)

Thus, bond strength of reactants should be weak in order to use lesser energy to break it, while bond strength of products should be strong to release more energy upon formation.

Qn 3:

Heat is the flow of energy from one object to another, or its surroundings (or the molecules’ total kinetic energy). An example will be boiling water in a kettle, where the surroundings of the kettle and the kettle itself turns hot =  heat can be felt)

Temperature is the measurement of how hot or cold something is (or measurement of the molecules’ average kinetic energy). An example is putting a thermometer into a kettle of water at room temperature, and boiling the water. The rise in temperature can be measured from the thermometer.

Just for info, some notable differences between heat and temp^[1]:

Qn 4:

(a) A high octane rating of 98 = knocking characteristic of 98% isooctane and 2%  heptane. The higher the octane number, the higher the resistance to knocking. The use of more branched chain isomers will also increase the resistance to knocking as well.

(b)

1. We need to find out the initial component of the premium gasoline.
2. From the initial component (which we know the octane rating), if its octane rating is lower than 98, it might indicate that oxygenated fuel additives may have been added to increase the octane rating. (Many oxygenated fuel additives have high octane rating of >100)

References:

1: Dathan CS. [Internet]. 2016. Methods of heat transfer and thermal properties of soil. [cited 2017 Feb 8]. Available from: https://www.slideshare.net/dathancs/methods-of-heat-transfer-and-thermal-properties-of-soil

The increasing ‘ozone hole’^[1]

References:

1: Bora C. [Internet]. 2016. Causes and Effects of Ozone Layer Depletion that are Painfully True. [cited 2017 Feb 1]. Available from: http://www.buzzle.com/articles/ozone-layer-depletion-effects-and-causes-of-ozone-depletion.html

The Ozone Layer helps by absorbing UV rays from the sun to reduce the heat from the sun to the surface of the earth. The production of CFCs(Chlorofluorocarbons) in the 1950s made the ozone deplete due to the CFCs breaking down Ozone in the stratosphere as shown below:

Fig. 1: Ozone in the earth and atmosphere ^[1]

Today, I have learnt that ozone is useful in stratosphere as it helps absorbs some UV radiation. I have also learnt about the wavelengths of gamma rays, UV, visible light, infrared radiation etc.

Reference:

1. WeatherSTEM. (2017). Ozone – Good up high, bad nearby!. [online] Available at: https://learn.weatherstem.com/modules/learn/lessons/93/07.html [Accessed 1 Feb. 2017].

However, if the ozone layer is depleted, it will become harmful to our environment 

Ozone is O3.