General Q&A for Class 12 · Page 194
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
How do you convert 293 K to Celsius?
To convert 293 K to Celsius: 293 - 273.15 = 19.85°C (approximately 20°C). This is a comfortable room temperature.
- GeneralClass 12All
How is 1°C equal to 1 K?
While 1°C is not equal to 1 K as absolute temperatures, a change of 1°C equals a change of 1 K. This is because both scales use identical unit intervals the difference between degrees is the same size. For instance, the difference between 20°C and 21°C is the same magnitude as the difference between 293.15 K and 294.15 K. However, as absolute values, 1°C equals 274.15 K.
- GeneralClass 12All
How do you convert between K and C?
Converting between Kelvin and Celsius is straightforward: Kelvin to Celsius: Subtract 273.15 (°C = K - 273.15) Celsius to Kelvin: Add 273.15 (K = °C + 273.15) Both scales increase at the same rate, meaning a change of 1°C equals a change of 1 K. The only difference is their starting points.
- GeneralClass 12All
How do you convert from Kelvin to Celsius?
To convert from Kelvin to Celsius, subtract 273.15 from the Kelvin temperature. The formula is: °C = K - 273.15. For example, if you have 300 K, you would calculate 300 - 273.15 = 26.85°C. This conversion works because the Kelvin and Celsius scales use the same unit size, but they start at different points Kelvin begins at absolute zero while Celsius begins at the freezing point of water.
- GeneralClass 12All
Does water freeze at 0°F?
No, water freezes at 32°F (0°C) at standard atmospheric pressure. 0°F (-17.8°C) is well below water's freezing point water is solid ice at this temperature. The Fahrenheit scale was originally designed with 0°F as the freezing point of a salt-water mixture, not pure water.
- GeneralClass 12All
Is 42 a high temperature?
Yes, 42°C (107.6°F) is dangerously high for body temperature and constitutes a medical emergency requiring immediate treatment. Sustained temperatures above 41°C can cause brain damage and organ failure. If this refers to environmental temperature, 42°C (107.6°F) represents extremely hot weather posing heat-related health risks.
- GeneralClass 12All
Is Snell's Law the Law of Reflection?
No, Snell's Law is not the law of reflection. The law of reflection states that the angle of incidence euals the angle of reflection (θᵢ = θᵣ), and both lie in the same plane as the normal. Snell's Law specifically deals with refraction (light bending when passing through different media), not reflection (light bouncing off a surface). However, both laws can be derived from Fermat's principle of least time.
- GeneralClass 12All
How Cv = f/2R?
For an ideal gas, Cv = (f/2)R, where: f = degrees of freedom (ways molecules can store energy) R = universal gas constant (8.314 J/mol·K) For example: Monatomic gases (f=3): Cv = 3R/2 Diatomic gases (f=5): Cv = 5R/2 This relates molecular motion to heat capacity.
- GeneralClass 12All
What is Cv chemistry?
In chemistry, Cv is the molar heat capacity at constant volume the amount of energy needed to raise 1 mole of a substance by 1°C when volume is held constant. It's particularly important for gases and thermodynamic calculations, typically measured in J/(mol·K).
- GeneralClass 12All
What is T in Gibbs energy?
In the Gibbs free energy euation G = H - TS, T represents absolute temperature in Kelvin. Gibbs free energy (∆G = ∆H - T∆S) predicts whether a reaction is spontaneous. Temperature affects the entropy term's contribution higher temperatures make the entropy factor more significant.
- GeneralClass 12All
What are the 4 units of heat?
The four common units for measuring heat energy are: Joule (J) - SI unit, standard in science Calorie (cal) - energy to raise 1g of water by 1°C; 1 cal = 4.184 J Kilocalorie (kcal or Cal) - dietary "Calorie"; 1 kcal = 1000 cal British Thermal Unit (BTU) - energy to raise 1 lb of water by 1°F; used in HVAC Joules are preferred in scientific work, while BTUs r
- GeneralClass 12All
What is 37.5 body temperature?
. 37.5°C (99.5°F) is slightly elevated and may indicate a low-grade fever. Normal body temperature ranges from 36.1°C to 37.2°C (97°F to 99°F), varying throughout the day and between individuals. 37.5°C warrants monitoring but isn't necessarily cause for concern unless accompanied by other symptoms.
- GeneralClass 12All
What is a fever of 39.5 Celsius in Fahrenheit for a child?
39.5°C euals 103.1°F this is a high fever in a child reuiring medical attention. Fevers above 103°F in children warrant contacting a healthcare provider, as they can indicate serious infection. Parents should also monitor hydration, other symptoms, and the child's responsiveness.
- GeneralClass 12All
Is 99.1 a fever in adults?
99.1°F (37.3°C) is borderline it's slightly above the traditional normal of 98.6°F but within the normal variation range for many people. A fever is typically defined as 100.4°F (38°C) or higher. If you consistently measure 99.1°F with symptoms like fatigue or aches, monitor it, but this alone doesn't confirm illness.
- GeneralClass 12All
Is 98.6°F the same as 37.4°C?
Almost 98.6°F actually euals 37.0°C (not 37.4°C). The 98.6°F figure is the traditional "normal" body temperature, though modern research shows normal temperature varies between individuals and throughout the day, typically ranging from 97°F to 99°F (36.1°C to 37.2°C).
- GeneralClass 12All
What is CP and CV?
Cp and Cv are heat capacities at constant pressure and constant volume: Cp (constant pressure) - heat capacity when pressure stays constant; usually larger Cv (constant volume) - heat capacity when volume stays constant; usually smaller For ideal gases, the relationship is Cp - Cv = R (gas constant). Cp is always greater because energy is needed both to raise temperature and to do expansion work against constant pressu
- GeneralClass 12All
What is heat capacity?
Heat capacity is the amount of heat energy reuired to raise the temperature of an object or substance by 1°C (or 1 K). It's measured in J/°C or J/K. Heat capacity depends on both the material and the amount—more mass means higher heat capacity. Specific heat capacity is the heat capacity per unit mass.
- GeneralClass 12All
What is C in = mcΔt?
c (lowercase) represents specific heat capacity the amount of energy reuired to raise the temperature of 1 gram (or 1 kg) of a substance by 1°C. Different materials have different specific heat capacities: Water: 4.18 J/g°C (very high) Iron: 0.45 J/g°C Copper: 0.39 J/g°C Water's high specific heat capacity makes it excellent for temperature regulation.
- GeneralClass 12All
Is eual to C Delta T?
Almost the complete formula is = mcΔT. You can also write it as = CΔT, where capital C represents the total heat capacity (C = mc), combining mass and specific heat capacity into one value. This simplified version is useful when dealing with objects of known total heat capacity.
- GeneralClass 12All
What does mc ∆t stand for?
In the euation = mcΔt: = heat energy transferred (joules or calories) m = mass of the substance c = specific heat capacity (amount of energy needed to raise 1 gram by 1°C) Δt = change in temperature This euation calculates the thermal energy reuired to change a substance's temperature without changing its state.