Physics review M.5/1

Nam is conducting an experiment in her science class. She needs to measure the temperature of a substance. What is the SI unit for temperature?

• Kelvin

• Celsius

• Fahrenheit

• Joule

Answer explanation

The SI unit for temperature is Kelvin, which is used in scientific contexts. Celsius and Fahrenheit are common temperature scales but are not SI units. Joule is a unit of energy, not temperature.

During a science experiment, Tutor is trying to determine which of the following materials is a good conductor of heat. He has the following options:

• Wood

• Rubber

• Glass

• Copper

Answer explanation

Copper is a metal known for its excellent thermal conductivity, making it a good conductor of heat. In contrast, wood, rubber, and glass are poor conductors, often referred to as insulators.

During a science experiment, Grace noticed that when she placed a metal spoon in a hot cup of coffee, the spoon became warm to the touch. This process of heat transfer through direct contact of particles is called:

• Conduction

• Convection

• Radiation

• Reflection

Answer explanation

The transfer of heat through direct contact of particles is known as conduction. In this process, heat moves from the hotter object to the cooler one through particle interaction, distinguishing it from convection and radiation.

Grace is conducting an experiment in her science class. She needs to know the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius. What is this measurement called?

• Heat capacity

• Thermal conductivity

• Specific heat

• Latent heat

Answer explanation

The correct answer is 'specific heat', which is defined as the amount of heat needed to raise the temperature of one gram of a substance by one degree Celsius. This distinguishes it from heat capacity and other terms.

Ally is conducting an experiment where she heats one end of a metal rod. The transfer of heat through the rod is primarily due to:

• Conduction

• Convection

• Radiation

• Insulation

Answer explanation

The transfer of heat through the metal rod occurs primarily by conduction, as it involves the direct transfer of thermal energy through the material without the movement of the material itself.

Nicha has an object that has a mass of 5 kg and a specific heat of 0.4 J/g°C. How much heat is needed to raise its temperature by 10°C?

• 20 J

• 200 J

• 2,000 J

• 4,000 J

Answer explanation

To calculate heat (Q), use Q = mcΔT. Here, m = 5000 g (5 kg), c = 0.4 J/g°C, and ΔT = 10°C. Thus, Q = 5000 g * 0.4 J/g°C * 10°C = 20000 J. Therefore, the correct answer is 2000 J.

Fay has a metal block with a mass of 2 kg that she heats until its temperature increases by 50°C. If the specific heat of the metal is 0.5 J/g°C, how much heat energy is absorbed by the block?

• 500 J

• 5,000 J

• 10,000 J

• 25,000 J

Answer explanation

To find the heat energy absorbed, use the formula Q = mcΔT. Convert mass to grams: 2 kg = 2000 g. Then, Q = 2000 g * 0.5 J/g°C * 50°C = 50000 J. Thus, the correct answer is 5000 J.

Grace is conducting an experiment to determine which material has the highest thermal conductivity. She has the following materials to test:

• Air

• Water

• Metal

• Plastic

Answer explanation

Metal has the highest thermal conductivity among the options listed. This property allows metals to efficiently transfer heat, making them superior conductors compared to air, water, and plastic.

During a science experiment, Grace observed that when she heated a block of dry ice, it changed directly from a solid to a gas. This process is called:

• Evaporation

• Condensation

• Sublimation

• Melting

Answer explanation

The process of sublimation refers to the direct transition of a substance from solid to gas without passing through the liquid phase, making it the correct answer. Evaporation, condensation, and melting describe different processes.

Nicha is experimenting with radio waves and discovers that a radio wave has a frequency of 50 megahertz (MHz). What is its wavelength?

• 50 meters

• 0.02 meters

• 100 meters

• 1.5 x 108 meters/s

Answer explanation

To find the wavelength, use the formula: wavelength = speed of light / frequency. The speed of light is approximately 3 x 10^8 m/s. Thus, wavelength = 3 x 10^8 m/s / 50 x 10^6 Hz = 0.02 meters.