Chem, Chapter 8, Energy
What's the specific heat of water?
4.18 J/g*C
How can heat be described?
As a flow of energy between two objects due to a temperature difference in the two objects(In an exothermic reaction, energy as heat flows out of the system into its surroundings. In an endothermic reaction, energy as heat flows from the surroundings into the system).
What happens in an exothermic reaction?
Energy is released to the surroundings as heat(Reactants start with higher potential energy and then when the reaction occurs, the products end with a lower potential energy).
What is the difference between temperature and heat?
Heat(energy) is the total energy of molecules in motion while temperature(speed of particles) is the measure of average energy of molecules in motion.
What are characteristics of a high and low specific heat?
High: they are hard to change states and have strong attractive forces Low: easy to change states and weak attractive forces
What is probably the most important characteristic of energy?
It is conserved(energy can be converted from one form to another but can not be created nor destroyed).
What is specific heat?
It's the highest heat point of a substance.
What is the greenhouse affect and what are the key molecules that cause it?
It's the process by which the radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. Carbon dioxide(CO2) and methane(CH4) are the key molecules that cause it.
If enthalpy is the heat for a reaction, it must have a sign as well as a magnitude. What sign should the enthalpy for an exothermic reaction have? Why?
Negative Delta H because the enthalpy of the products(or heat) is lower than the enthalpy of the system.
What do the different variables in Q=MC^T mean?
Q= Energy Transferred(J) M=Mass of Substance(g) C=Specific heat capacity(J/g x degrees Celsius ^T=Change in temperature(Degrees Celsius).
How is a food calorie different from the calorie we use in chemistry?
The calories seen on food packages are actually kilocalories(1 kilocalorie=1,000 calories). They are used to measure energy. A KCal is the amount of energy needed to raise the temperature of 1 kilogram of water 1 degree Celsius.
What happens in an endothermic reaction?
The system absorbs energy from its surroundings in the form of heat(Reactants start with a lower potential energy and then when the reaction occurs, the products end with a higher potential energy).
In our study of thermodynamics, we look at the changes in the internal energy of systems. To do so, we consider thermodynamic quantities to consist of two parts: What are they? Why do we take the system's point of view?
The system and the surroundings are the two parts of thermodynamic quantities. We use the system's point of view because it's where the reaction takes place. The surroundings are just everything else other than the system.
What indicates the vigor of the random motions of the components of a substance?
The temperature of a substance.
How are thermal, chemical, and phase energy stored?
Thermal: -energy of motion -measured by temp(higher temp=more Eth...faster particles) Phase: -energy stored in arrangement by states of matter -gasses have the most phase energy, then liquids, and lastly solids Chemical: -energy stored in arrangement of atoms in the molecules -more stable molecules have less Ech
How is heat transferred?
Through collisions and motion of particles.
What is the calorimeter used for?
To measure the heats of chemical reactions(The common units for heat are joules and calories).
True or False... There is only a transfer of energy between the system and surroundings when there is a change in Eth
True
True or false... Bonds are broken in endothermic reactions?.
True
True or false... water has the highest specific heat?
True
True or false... bonds are formed in exothermic reactions?
True.
