A solid maintains a fixed shape and volume due to closely packed particles. In contrast, liquids and gases take the shape of their containers, and plasma is an ionized gas with variable properties.

Sublimation is the process in which a solid turns directly into a gas without becoming a liquid first. The other options describe processes that involve liquid phases.

Solar energy is renewable because it harnesses energy from the sun, which is continuously available. Coal, natural gas, and nuclear energy rely on non-renewable resources or processes.

A balance scale is specifically designed to measure mass. The other instruments are used to measure temperature, length, and time respectively.

A thermometer is used to measure temperature accurately. The barometer measures atmospheric pressure, the hygrometer measures humidity, and the anemometer measures wind speed.

Melting of ice is a physical change because it involves a change in state from solid to liquid without altering the chemical composition. The other options lead to the formation of new substances and are chemical changes.

Newton's First Law, also known as the law of inertia, states that an object in motion will remain in motion unless acted upon by an external force. This explains why seatbelts are necessary to counteract the inertia during sudden stops.

The Ampere is the SI unit for electric current, representing the flow of electric charge. Volt measures electrical potential difference, ohm is used for resistance, and watt measures power.

The Conservation of Energy principle asserts that the total energy of an isolated system remains constant over time, merely changing forms. It is a fundamental concept in physics, unlike the other listed principles which pertain to motion or other phenomena.

Friction converts some of the kinetic energy of a moving object into thermal energy, which is why surfaces often heat up during motion. It does not change the mass of the object, affect gravitational force, or increase speed.

Potential energy is the energy stored in an object because of its position, arrangement, or state. This is distinct from kinetic energy, which is the energy of motion.

Boyle's Law states that the pressure and volume of a gas are inversely related when temperature is constant. Therefore, a decrease in volume leads to an increase in pressure.

A barometer is specifically used to measure atmospheric pressure. The thermometer measures temperature, while an altimeter and hydrometer are used for altitude estimation and liquid density, respectively.

Rusting of iron is a chemical change because it results in the formation of new compounds, such as iron oxide. The other processes are physical changes where the substance's chemical structure remains the same.

According to the wave equation (c = λν), if the speed of light remains constant and the frequency increases, the wavelength must decrease. This inverse relationship between frequency and wavelength is a fundamental principle in wave physics.

Acceleration is calculated by the change in velocity divided by the time over which the change occurs. Here, the car decelerates by 20 m/s over 4 seconds, resulting in an acceleration of -5 m/s².

The reaction CH₄ + 2O₂ → CO₂ + 2H₂O is a combustion reaction where a hydrocarbon reacts with oxygen to produce carbon dioxide and water. The other equations describe synthesis or decomposition reactions that do not involve combustion.

When brakes are applied in a car, the friction between the brake pads and the wheels converts kinetic energy into thermal energy. This is a clear demonstration of mechanical energy being transformed into heat.

Using the formula v = gt, where g is approximately 9.8 m/s², the velocity after 3 seconds is 9.8 x 3 = 29.4 m/s downward. This calculation reflects the continuous acceleration due to gravity.

Newton's second law states that acceleration is the force applied divided by the mass of the object. Here, 10 N divided by 2 kg gives an acceleration of 5 m/s².