| Advantages | Disadvantages |
| Can measure a wide range of temperature, from -100 deg C to 2500 deg C | Low sensitivity to small temperature changes |
| Can measure temperature at a point | Relatively low accuracy, degree of error is 1 deg C to 2 deg C |
| Rugged, not easily damaged | Prone to corrosion, due to two metals of different reactivity being in contact |
| Respond quickly to temperature changes | Low voltage output, which makes the output easily distorted by interference from nearby electronic devices. |
Category: FAQs
What is “inertia”?
Inertia refers to the reluctance of the object to change its state of rest or motion.
The bigger the mass of a body, the greater its inertia.
(ie, the bigger the mass, the more difficult it is to make a stationary object move, or to make a moving object change its speed or direction, due to its inertia)
State the Principle of the Conservation of Energy
The Principle of the Conservation of Energy states that energy cannot be destroyed or created.
It can only be converted from one form to another, or transferred from one body to another.
The total energy in the system remains constant.
Describe the structure of metals and metallic bonds.
The structure of metal consists of positive metal ions, arranged in a regular pattern, floating in a sea of delocalized electrons.
Metal atoms have the tendency to lose their valence electrons to form positive ions.
These valence electrons become delocalized and form a ‘sea of mobile electrons’ around the positive ions.
The strong electrostatic force of attraction between the positive metal ions and delocalized electrons form strong metallic bonds.
The layers of metal ions can slide over one another when sufficient force is applied.
In paper chromatography, the start line is drawn with a pencil rather than a pen. Explain the reason for this.
Pen ink consists of a mixture of dyes that can dissolve in the solvent and contaminate the chromatogram.
Pencil lead is usually made of insoluble graphite, which made it suitable for drawing the start line in paper chromatography.
Describe an experiment to determine the centre of gravity of an irregularly shaped thin plastic sheet.
a) Drill 3 small holes on the sheet, as near to the edge as possible, as far away from one another as possible.
b) Hang a plumb line from one of the holes.
c) When the sheet is stationary, trace the vertical line made by the plumb line using a marker.
d) Hang the plumb line from each of the other two holes and repeat the tracing of the lines.
e) The intersection point of the 3 traced lines is the centre of gravity of the plastic sheet.
Describe the test for sulfur dioxide gas.
Bubble the gas into acidified potassium manganate (VII) solution.
KMnO4 solution changes color from purple to colorless in the presence of sulfur dioxide gas.
State Newton’s Laws of Motion
Newton’s First Law of Motion (or Law of Inertia):
Every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it to change its state.
Newton’s Second Law of Motion:
When a resultant force acts on an object of constant mass, the object will accelerate and move in the direction of the resultant force. The product of the mass and acceleration of the object is equal to the resultant force.
Newton’s Third Law of Motion:
For every action, there is an equal and opposite reaction, and these forces act on mutually opposite bodies.
A metal sphere, mass 2kg, and a wooden sphere, mass 1kg, of the same size, are dropped at the same time from the same height of 5m, on Earth. Which sphere would hit the ground first? Explain.
Both spheres would hit the ground at the same time.
The spheres are dropped near to ground, so the effect of air resistance on the spheres’ resultant force is negligible.
The resultant force acting on the sphere will be its downward weight.
The ratio of the weight to mass will be 10 for each sphere, so both spheres will free-fall towards the ground at a constant acceleration of 10m/s2.
What are drying agents and what are the common drying agents?
Drying agents are substances that can be used to obtain a dry sample of a gas by removing its moisture content.
Examples:
* Anhydrous calcium chloride (for any gas except ammonia)
Ammonia will react with calcium chloride.
4NH3 (g) + CaCl2 (s) –> CaCl2.4NH3 (s)
* Concentrated sulfuric acid (for any gas except alkaline gases such as ammonia)
* Calcium oxide
(for any gas except acidic gases such as CO2 and SO2)