A substance has a melting point of -10°C and a boiling point of 50°C. At room temperature (25°C), it exists in which state? MCQ with Answer and Explanation
A substance has a melting point of -10°C and a boiling point of 50°C. At room temperature (25°C), it exists in which state?
A. Gas
B. Liquid
C. Solid
D. Plasma
Answer: Option B
Solution (By JKSSB Mock Tests)
Since the room temperature (25°C) is between its melting point (-10°C) and boiling point (50°C), the substance exists in the liquid state. If the temperature were below -10°C, it would be solid, and above 50°C, it would be gas. This is based on standard phase transition principles.
Explanation:
Calorific value is the heat produced by combustion of unit mass, expressed in energy per mass: kJ/kg, J/g, kcal/kg. Higher CV means better fuel. Determined by bomb calorimeter.
Explanation:
J.J. Thomson proposed the 'Plum Pudding' model in 1904 after discovering the electron. He envisioned the atom as a sphere of positive charge with negatively charged electrons embedded within it, like plums in a pudding. This was later disproved by Rutherford's gold foil experiment.
Explanation:
The thermite reaction involves aluminum powder reacting with iron(III) oxide to produce molten iron and aluminum oxide (2Al + Fe₂O₃ → Al₂O₃ + 2Fe). It is highly exothermic and is used for welding railway tracks and repairing metal structures in the field.
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