chapter 9 - thermal processes

Question 1

thermal equilibrium

Answer 1

describes a state in which two or more objects have the same temperature and that there is no net transfer of energy between them

Question 1

conduction

Answer 1

process of energy transfer where energy is transferred through the passing on of vibration motion from one particle to another

Question 2

convection

Answer 2

process of energy transfer by means of convection currents of a fluid (liquid or gas), due to a difference in density

Question 3

radiation

Answer 3

process of energy transfer by electromagnetic waves, without requiring a need for a medium

Question 4

why is a metal spoon colder to touch when placed in a cold room as compared to a wooden spoon?

Answer 4

both spoons will be cooled to the same temperature of the air-conditioned room (25 C) because they have been placed there for a long time. since our hands (37 C) are warmer than both spoons (25 C), energy is transferred through heating from our hand to the spoons (by conduction). even though both spoons are at the same temperature, the metal spoon feels colder than the plastic one because it conducts heat away from our hand more quickly than the plastic spoon.

Question 5

convection in a liquid or gas

Answer 5

when the water is heated, its volume increases and the warm water becomes less dense, allowing it to rise up the flask. as it flows through the flask, it cool down and becomes less dense. the cooler water sinks and gets heated by the bunsen flame at the bottom of the flask. a convention current is set up within the flask, causing energy to be transferred throughout the flask.

Question 6

characteristics of good emitters of radiation

Answer 6

high temperatures ; rough and matte surfaces ; large surface area ; dark coloured objects