Question

1. which energy transformation occurs when flipping on a light switch?

a) chemical to gravitational
b) mechanical to electrical
c) electrical to sound
d) mechanical to heat

1. friction causes some mechanical energy to be transformed into:

a) light
b) heat
c) sound
d) motion

1. which is an example of conduction?

a) sun warming your skin
b) boiling water in a pot
c) metal spoon heating in coffee
d) warm air rising in a room

1. which of the following is a closed system?

a) an open cup of coffee
b) a boiling pot without a lid
c) a cup of coffee with a lid
d) the atmosphere

1. what is the main reason a convection current forms in boiling water?

a) warm water rises and cool water sinks
b) water is heated by radiation only
c) the pot is metal
d) water molecules stop moving

1. what kind of energy transformation happens when a person eats food and then runs?

a) chemical to mechanical
b) mechanical to heat
c) electrical to light
d) gravitational to sound

1. which statement about heat transfer is true?

a) heat moves from cooler to warmer objects
b) heat moves from warmer to cooler objects
c) heat moves only in solids
d) heat always moves upward

1. which is an example of radiation?

a) metal spoon heating in coffee
b) sun warming your skin
c) boiling water in a pot
d) warm air rising in a room

1. when the suns energy reaches earth, it travels by:

a) convection
b) conduction
c) radiation
d) evaporation

1. temperature is a measure of:

a) the total energy of molecules
b) the average kinetic energy of molecules
c) the potential energy of an object
d) the energy lost as sound

Explanation:

1. Flipping a light switch is a mechanical action that results in electrical energy being used (to power the light). So it's mechanical to electrical.
2. Friction causes mechanical energy to be transformed into heat (e.g., rubbing hands together gets them warm).
3. Conduction is heat transfer through direct contact. A metal spoon in coffee (solid - liquid contact) is conduction. Sun - skin is radiation, boiling water (liquid movement) and warm air rising are convection.
4. A closed system doesn't exchange matter with the surroundings. A cup of coffee with a lid (prevents matter exchange like steam escaping) is closed. Open cup or boiling pot without lid exchange matter (steam), atmosphere is open (huge and exchanges matter).
5. In boiling water, warm (less dense) water rises and cool (more dense) water sinks, creating a convection current.
6. Food has chemical energy. When a person runs (mechanical motion), it's chemical to mechanical.
7. Heat moves from warmer to cooler objects (second law of thermodynamics). It can move in liquids (convection) and gases (convection), and not always upward (e.g., conduction in a horizontal bar).
8. Radiation is heat transfer via electromagnetic waves. Sun warming skin is radiation. Metal spoon (conduction), boiling water (convection), warm air rising (convection).
9. The Sun's energy reaches Earth via radiation (electromagnetic waves travel through space).
10. Temperature is a measure of the average kinetic energy of molecules. Total energy would be internal energy (sum of kinetic and potential of all molecules), potential energy of an object is different, and energy lost as sound is not related to temperature.

Answer:

1. B. Mechanical to electrical
2. B. Heat
3. C. Metal spoon heating in coffee
4. C. A cup of coffee with a lid
5. A. Warm water rises and cool water sinks
6. A. Chemical to mechanical
7. B. Heat moves from warmer to cooler objects
8. B. Sun warming your skin
9. C. Radiation
10. B. The average kinetic energy of molecules