When other elements are added to the pure metal, the different atomic sizes of the different elements disrupt the regular arrangement of the pure metal atoms. This irregular arrangement of the different atoms results in the alloys having different physical properties from their constituent elements. When a force is applied, the atoms in an alloy cannot slide over one another easily, causing the alloy to have lower malleability, lower ductility and higher strength as compared to pure metal.
Category: FAQs
Explain how combustion engines produce nitrogen oxides.
Fuels are combusted in internal combustion engines, producing a lot of heat.
The high temperature condition causes oxygen and nitrogen in the air to react to form oxides of nitrogen.
Describe the effect of temperature increase on the resistance of a metallic conductor.
The resistance increases as the temperature of a metallic conductor increases, so the resistance is directly proportional to the temperature.
When temperature increases, the amplitude of vibration of atoms increases. As a result, the number of collisions among the electrons and atoms increases, increasing the resistance to the flow of charges through the conductor.
Describe the pollution problems caused by the disposal of non-biodegradable plastics.
– Plastics are flammable.
In the event of a fire, plastic materials burn readily, causing the fire to spread quickly.
– Burning of plastics gives off toxic gases.
Many plastics produce poisonous gases upon incineration, causing air pollution.
– Plastics are non-biodegradable.
By “non-biodegradable”, it means that plastics cannot be decomposed by bacteria in the soil. Improper disposal of plastics can cause land and water pollution.
Describe what is meant by “wave motion”.
A wave motion is a movement or a disturbance through a medium, where the individual particles in the medium only vibrate vertically, horizontally, or in a cyclical pattern.
The wave motion can be illustrated:
– In a rope, when one end of a rope is moved in an up-and-down motion in a cyclical pattern.
– In a spring, when the spring is moved in an up-and-down motion, or a back-and-forth motion, in a cyclical pattern.
– In a ripple tank, when the dipper is moved in an up-and-down motion on the water surface, producing water waves.
What are the applications of esters?
Esters are used:
– in the manufacture of perfumes
– in the manufacture of artificial food flavorings
– as solvents for cosmetics and glues
– in the manufacture of soaps
Why must the temperature be kept at 37 deg C during fermentation of glucose solution?
At 37 deg C, the enzymes in yeast are the most active, so fermentation process will be fastest.
At low temperatures, the enzymes in yeast are inactive, so fermentation will be slow.
At high temperatures, the enzymes in yeast will be denatured, so fermentation will stop.
What is an addition reaction?
An addition reaction is a reaction in which new atoms are added to the organic compound by converting carbon-carbon double covalent bonds to carbon-carbon single covalent bonds.
Differences between boiling and evaporation
| Boiling | Evaporation |
| Occurs at a fixed temperature | Occurs at any temperature below boiling point |
| Quick process | Slow process |
| Takes place throughout the liquid | Takes place at the surface of the liquid |
| Bubbles form | No bubbles |
| Temperature remains constant | Temperature may vary |
| Thermal energy supplied by energy source | Thermal energy supplied by surroundings |
What is a homologous series?
A homologous series is a family of organic compounds with:
– same functional group
– same general formula
– similar chemical properties
– gradual change in physical properties
Examples of homologous series:
– Alkanes
– Alkenes
– Alcohols