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7.2 The Nature of Energy: Key Definitions -- Part 1
The heat and work associated with a chemical reaction can be seen in a potato cannon.
A potato is stuffed into a cylinder that is capped on one end and open on the other side of a potato cannon.
Fuel is introduced under the potato at the capped end through a small hole.
The cannon emits heat to the surroundings when the potato shoots out of it.
An external flame warms a cylinder and piston assembly.
The contents of the cylinder expand when pushed against the external pressure.
The thermal energy flows from matter to matter.
As coffee cools down, it transfers thermal energy to the lower- temperature surroundings.
They transferred thermal energy to the coffee because it got hotter.
The transfer of heat from a hotter object to a colder one is a fundamental principle discussed in Chapter 19 and is related to the second only in our imaginations.
The thermal energy in the coffee is transferred to the surroundings.
There is no net transfer of heat at thermal equilibrium.
A steel saucepan is being put on a kitchen flame.
The values of the specific heat capacity are listed in Table 7.4.
The units of heat capacity are J>mol.
Changing the temperature of water requires a lot of heat, and it has the highest specific heat capacity of all the substances in Table 7.4.
If you've ever traveled from an inland region to the coast during the summer, you've experienced the effects of water's high specific heat capacity.
On a summer's day in California, the temperature difference between the inland city of Sacramento and the coastal city of San Francisco may be as large as 18 degrees C (30 degrees F).
The intensity of sunlight falling on these two cities is the same.
San Francisco is surrounded by the water of the Pacific Ocean.
Water has a high heat capacity, so it keeps San Francisco cool.
Sacramento is about 100 miles inland.
The land surrounding Sacramento has a low heat capacity, which causes it to rise in temperature.
Only two U.S. states have ever recorded a temperature over 100 degrees.
Alaska is obvious.
It's too far north to get that hot.
The other may come as a surprise.
The high heat capacity of the water prevents Hawaii from getting too hot.
The relationship between the amount of heat added to a given amount of the substance and the corresponding temperature increase can be quantified using the specific heat capacity of a substance.
If you find a penny in the snow, it might beinted before 1982.
The penny has a mass of 3.10 g.
The units are correct for heat.
A chemistry student decides to measure the heat capacity of a shiny gold-colored rock to see if it is actually gold.
She first weighs the rock and finds it has a mass.
Determine the heat capacity of the substance that composes the rock and see if the value is consistent with the rock being pure gold.
725 J of heat can be absorbed by a 55.0-g aluminum block.
There is a large water jug and a rock near the fire.
As it cools, the water will release more heat.
The rock will absorb more heat as it cools.
As it cools, the rock will release more heat.
As it cools, the water will absorb more heat.
When two substances of different temperature are combined, thermal energy flows as heat from the hotter one to the cooler one.
A block of metal should be submerged into the water at 55 and 25 degrees.
When the two substances reach the same temperature, the metal becomes cold and the water becomes warm.
The exact temperature change depends on the metal's mass and the water's heat capacities.
A cube of aluminum is submerged at a temperature of 45.8 degrees.
Their initial temperatures were 105.3 g.
The final temperature for both substances will be the same.
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