heat and work

Conduction requires

• Electricity

• the electromagnetic spectrum and particles

• air or water flow

• direct contact

What is the definition of CONDUCTION?

• When heat is transferred from objects like rays of light or electromagnetically.
• a  hot liquid or air that  expands, becomes less dense, and rises or becomes more dense, and sinks.
• When heat transfers from objects that are touching.
• When heat transfers through the heater or AC in your house.

The earth receives heat energy from the sun by _______________, which is the transfer of energy as electromagnetic waves?

• radiation
• convection
• conduction
• greenhouse effect

Convection can take place in _________________.

• solids only

• liquids only

• liquids and gases only

• solids, liquids and gases

In a situation where the internal energy increases, is the work done on the system positive or negative? Explain.

• Positive, because work is always done on the system when the internal energy increases

• Negative, because work is always done by the system when the internal energy increases

• Positive, because work is always done by the system when the internal energy increases

• Negative, because work is always done on the system when the internal energy increases

Explain how heat transfer affects the internal energy in a process of heating water.

• Heat transfer increases the internal energy of the water

• Heat transfer decreases the internal energy of the water

• Heat transfer has no effect on the internal energy of the water

• Heat transfer can either increase or decrease the internal energy of the water

Provide a practical example where heat transfer decreases the internal energy of a system.

• Boiling water in a kettle

• Rubbing hands together to warm them

• Melting ice in a glass

• Cooling a hot cup of tea by blowing on it

What is the change in internal energy of a cup of coffee that initially has a temperature of 85°C and then cools down to 65°C in 10 minutes, losing 2000 J of heat during the process?

• Change in internal energy: -2000 J

• Change in internal energy: 2000 J

• Change in internal energy: -2508 J

• Change in internal energy: 2508 J

What is the change in internal energy of a motor that performs 6000 J of mechanical work while releasing 1500 J of heat due to internal friction?

• Change in internal energy: -4500 J

• Change in internal energy: -7500 J

• Change in internal energy: 4500 J

• Change in internal energy: 7500 J

What is the change in internal energy of a block of ice that initially has a temperature of -10°C and is heated until its temperature reaches -2°C, with 4000 J of heat added to the block of ice?

• Change in internal energy: -4000 J

• Change in internal energy: 4000 J

• Change in internal energy: -2508 J

• Change in internal energy: 2508 J