Question

1. what is the definition of convection?

a. when heat transfers through waves.
b. when heat transfers from objects that are touching.
c. a hot liquid or air that expands, becomes less dense, and rises or becomes more dense, and sinks.
d. heat traveling from the sun

1. the baby chickens are kept warm from the heat lamps demonstrates this type of heat transfer.

a. conduction
b. convection
c. radiation

1. walking on the warm sand sand with your bare feet demonstrates this type of heat transfer.

a. conduction
b. convection
c. radiation

1. how does heat travel from hot to cold?

a. particles
b. the atoms of a hot substance move and collide with cold atoms
c. molecules are packed together
d. the particles leave enough room for expansion

1. some students observing a classroom device being used, noticed the below energy transformations.

electrical → mechanical → sound
which device were the students most likely observing?
a. a triple beam balance measuring an object’s mass.
b. a pencil sharpener plugged into a wall outlet.
c. a projector displaying a diagram on the screen.
d. a working flashlight used to light up a dark corner.

1. which of these is an example of light energy being transformed into chemical energy?

a. a glow stick lights up when broken.
b. water heated by the sun evaporates.
c. a plant makes sugar in the sunlight.
d. a battery causes a buzzer to vibrate.

Explanation:

Question 24

• Option A: Heat transfer through waves is radiation (e.g., electromagnetic waves), not convection. Eliminate A.
• Option B: Heat transfer from touching objects is conduction. Eliminate B.
• Option C: Convection involves the movement of fluids (liquids or gases) where hot fluid expands, becomes less dense, rises, and cool fluid (more dense) sinks. This matches the description.
• Option D: Heat from the sun is radiation. Eliminate D.

• Conduction requires direct contact. Heat lamps don’t touch the chickens, so A is out.
• Convection involves fluid movement; heat lamps don’t rely on fluid motion here. Eliminate B.
• Radiation is heat transfer via electromagnetic waves (e.g., infrared from heat lamps), which warms the chickens without direct contact. So C is correct.

• Walking on warm sand involves direct contact between feet and sand. Conduction is heat transfer through direct contact of particles.
• Convection (B) is fluid-based, and radiation (C) is wave-based (no contact). So A is correct.

Answer:

C. A hot liquid or air that expands, becomes less dense, and rises or becomes more dense, and sinks.

Question 25