In a cold pack, an endothermic reaction draws heat from the surroundings, although there are several different types of cold packs, some with different reactions.
In the atom, the nucleus is charged positive and the electron is charged
negative. So we know that they're attracted to each other. It takes energy
to keep the electron from falling into the nucleus.
-- If you want to drag the electron farther out from the nucleus, you have to
do work on it ... put energy in to it.
-- When the electron loses energy, it falls in closer to the nucleus. The more
energy it loses, the closer to the nucleus it falls.
-- From the list of choices in the question, the <span>electron moving <em>two energy levels </em>
<em>closer to the nucleus</em> loses more energy than any other choice.
</span>
Answer:
We know that the length is 79 (there are no units of length in the question, so i will leave it as it is written, without units) when the temperature is 2°C.
We want to find the increase in length when the temperature is 35°C, knowing that the linear expansion coefficient is 11*10^(-6) °C^-1
The change in length is just given by the equation:
where:
α = 11*10^(-6) °C^-1
T₀ is the initial temperature, so T₀ = 2°C
T₁ is the final temperature, so T₁ = 35°C
L₀ is the initial length, so L₀ = 79
Replacing these in the equation we get:
ΔL = ( 11*10^(-6) °C^-1)*79*(35°C - 2°C)
= 0.28677
So the length of the railroad will increase by 0.28677