Enter your Sign-on user name and password.

Forgot password?
  • Follow us on:
Loading video...
Text Comments (8)

0 answers

Post by Leili Reza on December 8, 2012

thanks

1 answer

Last reply by: Professor Ebs
Fri Apr 19, 2013 2:31 PM

Post by Antoni Szeglowski on January 21 at 08:31:21 PM

So thermal energy is basically total energy?

1 answer

Last reply by: Professor Ebs
Fri Apr 19, 2013 2:42 PM

Post by Yisrael Harris on April 18 at 12:48:58 AM

I don't see how convection is a type of heat transfer. The actual transfer of heat seems to still be conduction: from the heated pot to the water. The fact that molecules undergo this current as they become less and more dense doesn't seem to be a transfer of heat, but rather an additional phenomenon taking place as a side-effect of the conduction.

Moreover, in the explanation given, from what to what is the heat being transferred? I think that part of the explanation is missing: as the heated molecules rise, other molecules are now at the bottom and they now become heated. In addition, presumably, as the heated molecules rise, they pass some of their heat to other molecules. (Otherwise, as they lose their heat when they rise, what are they losing that heat to?)

Bottom line, though, the actual transfer of heat would still seem to be conduction. The convection is not transfer of heat per se, but rather a phenomenon that facilitates the conduction.

0 answers

Post by Yisrael Harris on April 18 at 12:59:53 AM

What is the arrangement of atoms in a liquid? Is it at all similar to the solid, or completely random? Are the differences between the arrangement and motion of molecules in a liquid and gas quantitative or qualitative? If merely quantitative, then what is it that gives a gas such a distinctly different appearance to us from a liquid? If indeed qualitative, then what is the nature of that qualitative difference?

1 answer

Last reply by: Professor Ebs
Fri Apr 19, 2013 3:00 PM

Post by Yisrael Harris on April 18 at 01:10:10 AM

In the section on changing states of liquid, on the graph where point B is a solid and point C is a liquid, what is the state of the substance between points B and C?

Heat and States of Matter

  • The average kinetic energy of a substance is the temperature of the substance.
  • The units used for temperature are Kelvins (K) and degrees Celsius (°C).
  • Thermal energy is the sum of the kinetic and potential energies of the particles in the matter.
  • Thermal energy is affected by state of matter, temperature of matter, and amount of matter.
  • Heat is thermal energy that is transferred from an object at a higher temperature to an object at a lower temperature.
  • Heat moves from warm to cool until the two objects are equal temperatures.
  • Specific Heat – Objects change temperature at different rates when the same amount of heat is added. Measure specific heat as the amount of thermal energy needed to increase 1kg of a substance by 1°C.
  • Thermal expansion occurs as a substance’s temperature is increased. The particles of a substance move faster and move away from each other.
  • Heat is transferred by radiation (waves or rays), conduction (direct contact), and convection (currents in a liquid or gas).
  • In a solid, particles are arranged in repeating patterns and solids have a fixed volume and shape. Particles are further away in a liquid that has a fixed volume and takes the shape of the container. Particles are even further apart in a gas that takes the volume and shape of the container.

Heat and States of Matter

When writing a chemical equation, the (1,0)20 are on the left side of the reaction arrow and the (1,0)20 are on the right side.

Reactants/Products

In a chemical reaction, is the mass of the products greater than, equal to, or less than the mass of the reactants?

Equal – law of conservation of mass

What is used in a chemical equation to indicate how many units of each compound are present?

A coefficient

Translate the following equation into words: Na(s) + Cl2 (g) → 2NaCl (s)

One unit of solid sodium plus one unit of diatomic chlorine gas yields two units of solid sodium chloride.

What is the goal when you are balancing equations?

To get the same number of atoms on each side of the reaction – To follow the law of conservation of mass to make sure that no atoms are gained or loss in the reaction.

Balance the following equation: CH4 + O2 → CO 2 + H2O

CH4 + 2O2 → CO2 + 2H2O

What are 6 things you can do to increase the rate of a chemical reaction?

Increase the temperature, pressure, or concentration, add a catalyst, increase the surface area of a reactant, or agitate (stir or shake).

In (1,0)20 reactions, products have more energy than reactants and in (1,0)20 reactions, reactants have more energy than products.

Endergonic/Exergonic

In chemical reactions, how is energy lost or gained?

Heat, light, sound or electricity

Identify the type of the following reaction: H2SO4 + 2 LiOH → Li2SO4 + 2 H2O

Double displacement

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.

Answer

Heat and States of Matter

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

Chemistry: Physical Science

Related Books & Services