Temperature/ Heat
What is another name for thermal energy?
Heat
Where are reactants and products located at on an energy diagram?
Reactants are located the start (on the first flat line), and the products are located at the end (on the last flat line)
Complete the equation:
Q = ????
Q = mcΔT
How much energy is lost when 200 grams of water is cooled from 25 °C to 10 °C? (c of H2O is 4.184 J/g°C)
-12,552 J
or 12,552 J of energy are LOST.
Is what direction does heat flow?
From hot to cold.
What type of energy is associated with motion?
Kinetic energy
Mechanical energy
How do you calculate ΔH?
ΔH = H of products - H of reactants
What is the equation to calculate ΔT?
ΔT= Tf - Ti
A block of copper (specific heat=0.385 J/g°C) requires 6,250 J of thermal energy to change in temperature from 27°C to 139°C. What is the mass of the block?
144.94 g
What happens to the temperatures of two touching objects during thermal equilibrium?
The temperatures will equalize to the same number.
What type of energy do chemicals have before/after a reaction has completed? (choices= potential energy or kinetic energy)
What type of energy does a wheel spinning around have? (choices= potential energy or kinetic energy)
chemicals= potential energy
wheel spinning= kinetic energy
True or False:
If the potential energy of the products in less than the potential energy of the reactants on a diagram, the ΔH value will be positive.
False, the ΔH value should be negative because it is an exothermic reaction.
True or False:
If Q is positive, then ΔT will also be positive.
True. Q and ΔT will always match in sign.
What is the temperature change of a block of brass if the block weighs 134 g and absorbs 1,496 J of energy? The specific heat capacity of brass is 0.380 J/g°C
Δt= 29.4 °C
What is the difference between an endothermic and exothermic reaction?
An endothermic reaction absorbs heat while an exothermic reaction releases heat.
What type of energy changes occur in the following scenario and why?
"You get hungry while riding a skateboard. Your tire gets stuck in a crack while trying to stop ejecting you from the skateboard, you skid on the sidewalk and skin your knee"
chemical energy from your body is converted into mechanical energy of the moving skateboard.
then it becomes mechanical energy of your body moving while ejected.
then it becomes mechanical and thermal energy of your knee skidding/scraping against the ground which produces friction.
What does a catalyst change on an energy diagram and what does a catalyst not change?
A catalyst will change the transition state and activation energy of a diagram, but it will not change the original energy of the reactants and the final energy of the products.
What is the definition of "c" (specific heat capacity)?
The amount of energy required to raise 1 gram of substance by 1 °C.
What is the specific heat capacity of substance that requires 99,100 J of thermal energy to heat 3470 g of the substance from 11°C to 45°C
0.839 J/g°C
What is the difference between heat and temperature?
Heat is how much thermal energy is present, and it flows from hot to cold.
Temperature is a measurement of the thermal energy that allows particles to move around.
What happens (in detail) when a block of hot iron is placed into a beaker of cold water?
(You must include words like thermal energy and thermal equilibrium)
Where is the transition state located on an energy diagram AND how do you calculate the activation energy (Ea) of an energy diagram?
The transition state is located at the highest point on the curve.
To calculate activation energy, you determine the increase (or difference) in energy from the reactants up to the transition state
Ea= T.State- Reactants
describe what each of the letters in the following equation refer to AND what units they have:
Q = mcΔT
Q = energy (J)
m= mass (g)
c = specific heat (J/g°C)
ΔT = change in temperature (°C)
What is the final temperature of a 150 g sample of water when 10,000 J of energy is absorbed if its initial temperature was 20°C? (c of H2O is 4.184 J/g°C)
35.9 °C
You have to solve Q=mcΔt for t first, and then plug it into Δt=tf -ti to solve for tf