Thermal | MCQs

Explanation

• Thermal Contraction is the decrease in size (length, area, and volume) of a body due to a decrease in temperature.
• Thermal Expansion is the opposite phenomenon, where the size increases due to an increase in temperature.

Explanation

• Thermal Expansion is the natural increase in size of a substance as its temperature increases.
• It's a common phenomenon in solids, liquids, and gases.

Explanation

Thermal energy can be transferred through all three methods:

• Conduction: Direct transfer between particles in physical contact.
• Convection: Transfer through the movement of fluids.
• Radiation: Transfer through electromagnetic waves (e.g., light, radio waves).

Explanation

• Refrigerators work on the principle of heat transfer through conduction, convection, and radiation.
• They use a combination of these methods to transfer heat from the inside to the outside, keeping your food and drinks cool and fresh.

Explanation

• During nighttime, the air above the land loses heat and cools down, causing its density to increase.
• This is because cool air contracts and becomes denser than warm air.

Explanation

• Convection is the primary mode of heat transfer in liquids and gases, where heat is transferred through the motion of fluids.
• This motion creates circulation currents that carry heat energy from one location to another.

Explanation

• Copper is an excellent conductor of heat, having a high thermal conductivity (386 W/mK).
• This means it can efficiently transfer heat energy with minimal resistance.
• Metals (e.g., iron, copper, silver, mercury, aluminum) are good conductors of heat.

Explanation

• A change in physical appearance or state of a substance, such as a change in shape, size, color, or phase (solid, liquid, gas), is called a Physical Change.
  

The are examples of Physical Changes:

• Melting (ice cream, wax, chocolate, ice and change from solid to liquid)
• Phase changes (boiling, freezing, condensation)
• Crushing (chalk)
• Tearing (paper)
• Crumpling (aluminium foil)
• Stretching (rubber band)
• Mixing (sugar in water)
• Dissolving (sugar, salt in water)
• Moulding (clay, metals)
• Slicing (fruit)
• Forming of frost (from water vapors)
• Transition to a gas (change from liquid to gas)
• Change of durability (change in texture or strength)
• Changes to crystal form (change in crystal structure)

Explanation

A change in physical appearance or state of a substance, such as a change in shape, size, color, or phase (solid, liquid, gas), is called a Physical Change.

Explanation

• A release of gas is typically a sign of a chemical change, not a physical change.

The signs of physical change:

• Change that can be reversed
• The substance does not turn into a new substance