Cloning makes an identical copy of the dog, while breeding generates a new dog species by reproduction. Cloning merely produce genetic copies of the pet dog, and does not introduce any improvements. Also, cloning results in uncertainties in the health and life span of the clone.

Pros – it can help to solve the problem of drought and famine by reducing our dependence on naturally grown corn and traditional corn-growing methods. These GMO corn may have higher yield and could thrive in harsh conditions.

Cons – people might develop food allergy; pests have evolved under the selective pressure of corn that are more resistant to pests, or can produce its own insecticide, making it difficult or impossible for non-gmo corn or crops to be grown in the future.

a. C6H12O6 = 6 C + 6 H20 = C6(H20)6

b. –

c. No. Fructose can form 2 types of isomers: 5-membered ring or 6-membered ring isomers. The 6-membered ring form of fructose is sweeter, while the 5-membered ring form tastes about the same as usual table sugars. Isomers differ in their physical and chemical properties and hence it can be expected that they differ slightly in their sweetness.

An example of a chemical substance is water, H20. It is impossible for anyone to survive without consuming water.

The contents of Organic Foods should be 95% or more certified organic, meaning free of synthetic additives like pesticides, chemical fertilizers, and dyes, and must not be processed using industrial solvents, irradiation, or genetic engineering, according to the USDA, and the remaining 5% may only be foods or processed with additives on an approved list. Moreover, organic foods do not necessarily refer to ‘pesticide-free’ or ‘chemical-free’ produce, but that the chemicals and pesticides used are derived from natural sources. Chemicals are not only inescapable – they are present in all the food we consume, but they are also not always bad. Also, anything can be toxic in large enough quantities.

For instance, a banana is found to contain almost 50 chemicals, and yet, it is a fruit that has high vitamin C content and has health benefits.

The polymer is dissolved by the acetone, which releases the gas of the foaming agent. A foaming agent is used to make it easier to make foam by reducing the surface tension of a liquid. The loss of the foaming agent causes the polymer to collapse on itself, resulting in it becoming denser. Polymer chains can rearrange into a more condensed structure following the removal of the air bubbles, which are caused by the foaming agent.

The main difference between LDPE and HDPE is their structure. HDPE are more linear than LDPE. Depending on the shape of the polymer, their physical properties may be very different (even when they are composed of the same number of the same molecules).

a. Branched LDPE (Low Density Polyethylene) cannot be used because it cracks easily under stress (fragile). It is soft, stretchy but not very strong. Hence, it is not good to protect against cuts.

b. HDPE (High Density Polyethylene) has little branching and hence has stronger intermolecular forces and tensile strength than LDPE. It is harder, denser an stronger than LDPE.

No, it does not. This is because the weak but extensive dispersion forces in plastics allow the molecules to slip pass one another and ‘stretch’, making the polymer longer with reduced thickness. Dispersion forces are weak Van Der Waals forces of interaction, which can be broken easily. On the other hand, paper is made from cellulose fibres, which have high tensile strength due to the presence of covalent cross-linkages between the glucose polymers. Therefore, the chemical bonds and structures in paper makes paper resistant to stretching.

a. Biocompatibility – material must be biologically compatible and must not elicit local or systemic responses from the living tissues or systems; Non-toxic; Hydrophilicity – material must be ‘water-loving’ so that cells are able to attach onto the polymers (but there are some that must be hydrophobic as well); Porosity – ratio of the pore volume to total volume, must enable substances or molecules to pass through if the body part that it is replacing has those properties; Degradability – if it is used to replace the body part permanently, it must be able to withstand the conditions within the body and not be degraded or broken down, e.g. acidity, alkalinity, enzymes; mechanical properties – changes depending on its use within the body.

b. Contact lenses are made from silicone hydrogel. Some desirable properties involve the materials being soft, durable and transparent. Moreover, it has to have an appropriate refractive index.

c. The ‘hard’ material that is used in contact lenses is Poly methyl methacrylate (PMMA), and it makes it uncomfortable to wear contact lenses as it is rigid. It does not allow air to pass through. On the other hand, the ‘soft’ material is silicone hydrogel, which makes wearing contact lenses comfortable. It is soft, flexible and allows air passage.

There can be carbon isotopes which differ in the number of neutrons present, and they can differ in charges (ions) – positive or negative charges, depending on the conditions.

Carbon and uranium are completely different elements. The carbon atom differs from all uranium atoms in terms of its atomic mass, neutrons, electrons and protons.

Both are Nitrogen atoms, but they differ in the number of neutrons. They differ in the reactivity as well.
14N has 7 protons, 7 electrons and 7 neutrons.
15N has 7 protons, 7 electrons and 8 neutrons.

a. 94 protons

b. 93 protons = Neptunium, 94 protons = Plutonium

c. 86 protons

A – Control Rods
B – Cooling water out of the core
C – Control Rod Assembly
D – Cooling water into the core
E – Fuel Rods

It is very expensive and yet is not a very efficient process – not energy-efficient. The residue is very saline brine, which is hard to dispose of without causing too many environmental problems.

Water-soluble vitamins are polar compounds while fat-soluble vitamins are non-polar compounds. For vitamins to be water-soluble, they have to form favorable bonds with water molecules, such as ion-dipole interactions. These vitamins are also hydrophilic. On the other hand, lipid molecules are hydrophobic and can form Van Der waals forces of interactions. Hence, fat-soluble molecules have to be able to form these interactions as well. Like dissolves like; therefore polar compounds can only be dissolved in polar solvents while non-polar compounds can only be dissolved in non-polar solvents. Vitamins differ in the functional groups they have, and some functional groups can add polarity to the vitamin compound. An excess of water-soluble vitamins will be removed from the body through the urine, while an excess of fat-soluble vitamins will be accumulated in the fat molecules (lipids) in the body, and this can be potentially harmful for the individual.

Acid rain is caused by SOx and NOx dissolving in water and increasing the acidity of rain.
a, c and d are examples of how we can reduce electricity usage, which in turn reduces the amount of coal burnt. Since coal contains 1-6% sulfur, this reduces the amount of SOx produced and then simultaneously released into the atmosphere.
b and e are examples of how we can reduce transportation needs, which reduces the amount of NOx produced from automobile traffic.

a. The coal-fired plant will churn out smoke, ash and huge amounts of water vapor (hydrogen and carbon from coal makes more water vapor) that contributes to fog, and then causes poor visibility. There are also small droplets of SO3 (sulfur oxides), which creates smog.

b. The neutral pH of rain is around 4-5, which is one pH value lesser than the normal pH of rain, 5-6.

Intermolecular forces are broken.

a. Exothermic
It is exothermic as it releases energy when it burns. It causes us to feel warmer when we are around it.

b. Endothermic
It is endothermic as it absorbs energy to evaporate. When water evaporates from our skin, we tend to feel cold. This is consistent with the fact that endothermic processes causes its surroundings to become colder.

c. Endothermic
It is endothermic as it absorbs energy to melt – it undergoes a change of state from solid to liquid state. This means that bonds were broken between the water molecules in solid state to give rise to a more disordered liquid state. Bond breaking requires energy (it absorbs energy). When we place ice at room temperature, or in room temperature drinks, they absorb the energy of the surroundings and melt. This in turn makes the drinks colder.

For chemical explosions to be exothermic, they have to release energy to its surroundings. This means that the energy used for bond breaking (of the reactants) must be very small and the energy used for bond forming (of the products) is very large; this means the energy released would be a lot. The products of the reaction should be of a lower energy than the reactants. Hence, the products of such exothermic reactions are typically gases.

Heat is the consequence of motion at the molecular level, and temperature is the measure of average speed of the motion. Temperature determines the direction of heat, which flows from a warmer body to a colder body. Heat is a form of energy.

Temperature can be measured directly using a thermometer. However, to measure heat, we need to know the mass, specific heat capacity and temperature of the compound.
When we apply heat to water and the water boils, we can observe bubbles (water vapour). Temperature rises at the same time.

Knocking is the likelihood of the compound undergoing preignition, where the fuel-air mixture ignites before sparking, when compression occurs. It is affected by the different chain lengths.

a. Unlikely to knock as it has a knocking characteristic of 98% isooctane (branched) and 2% heptane (straight-chained). This gasoline behaves like a mixture of these two compounds.

b. Adding oxygenates to gasoline increases the gasoline’s octane rating. Hence, it can be deduced that the fuel contains a good amount of oxygenates.