section 4.7 chem talk

In this chem talk we learn about enthalpy change which is the change in heat energy. If the change is negative the reaction is exothermic and if the change is positive then the change is endothermic. The bump is the height of the reactant energy. This is called the activation energy and is always positive. The top part, which is the state in-between the reactants and products is called the activated complex.  the last thing talked about in the chem talk is the catalyst.  This is a substance that provides a lower energy pathway for a reaction which increases the speed of a reaction.

section 4.7 checking up questions

  1. For a change to occur spontaneously, a chemical reaction continues to occur on its own once it begins.
  2. If it still happens and “How fast it happens determine if a change can occur spontaneously.
  3. To tell if it is exothermic or endothermic, you have to look at the locations of the reactant energy and project energy which indicates whether the overall enthalpy change is either one.
  4. Energy in an exothermic reaction comes from if the starting point is higher than the ending point and then the system releases heat energy to the surroundings.
  5. Two things that chemists use to speed up a reaction in a MRE heater is something with more surface area and something that can act as a catalyst, like iron.
  6. A catalyst provides a lower-energy alternative pathway for the reaction to take so they have enough energy to get over the energy barrier.
  7. When there is a catalyst the barrier is smaller so it is easier to get over but when there isn’t a catalyst the barrier is bigger and the bump is harder to get over. In the end the products go down and end in the same place.

section 4.6 checking up questions 1-5

  1. NaCl conducts electricity because when the crystal s dissolve in water the sodium ions and chloride ions separate from the crystal. They can move around in water. Molecular compounds don’t break up into ions when they dissolve.
  2. An electrolyte is a substance that dissolves in water to make solutions that conduct electricity and non-electrolytes are molecules that do not form ions in a solution.
  3. The Zinc electrons come from the zine metal and travels through the wire.  the electrons reach the copper and then the copper takes them. after this, reduction takes place.
  4. The anode of a battery is when oxidation takes place and the electrons are released into the circuit. The anode is negative when it is giving away.
  5. The cathode of the battery is where reduction takes place and the electrons are received. The cathode is positive when receiving. At the end electrons are received. 

Section 4.6 chem talk

In this chem talk we learned about many different ideas.  We also learned about new substances.  One of these new substances is electrolytes. this is a solute that forms ions in an aqueous solution.  We also learned about ion which are atoms that have acquired a charge by either gaining or losing an electron.  Another substance is non-electrolytes.  These are solutes that do not form ions in solutions.  The chem talk talks about half cells.  Two half cells make up one battery.  This is very interesting because we see how batteries are formed.  The half cell where oxidation takes place is called the anode.  And the half cell where reduction takes place is called the cathode.  It is interesting how there are different half cells for different purposes.

section 4.4 chem talk

In this chem talk e learned about metals which are materials that exhibit the properties of conductivity.  We learn about Oxidation reduction reactions which are chemical reactions in which electrons are transferred from one substance to another.  This is interesting because it shows how to transfer electrons in a chemical equation.  oxidation is a loss of one electron while reduction is a gain of an electron.  This is interesting because it is a new concept that allows us to transfer electrons in chemical equations in a simple way.

section 4.3 chem talk

In this reading we learn about a completely new concept, stoichiometry.  Stoichiometry is the study of relationships among substances.  This is interesting because you can use this to find the number of moles of one chemical reaction.  A mole is counting word to count very large quantities of very small objects.  This is also interesting to me because 1 mole of something is that same for any object.  This mean that one mole of two different objects will be the exact same.  We also learn about molar mass which is the mass of one mole of a pure substance.  This chem talk was very interesting because it shows how to calculate the quantity of small objects in a simple way.

Section 4.2 chem talk

In this chem talk we learn about the laws of conservation of matter.  This is the amount of matter present before and after a chemical change remains the same.  We learn how when chemical equations are written, the quantity of an element must be the same on both sides.  We learn how 2500 years ago this was discovered by greek philosophers.  This is interesting to me how they were able to figure this out way back then.  

Section 5.2 Chem Talk

  1. Most gases have little attraction between their molecules because the molecules are very far apart from each other in a gas. The shape of the nonpolar molecule causes this and since a gas has a shape with the molecules spread out very much, their is little attraction between each other.

2. a.polar      b. nonpolar   c. nonpolar

3. b,c,a       

4. The intermolecular forces in water are stronger than the ones in methane. 

chapter 5 section 2 chem talk

In this reading we learn about how the particles in solids are not able to move around a lot due to their strong attraction to each other.  We also learn about non polar molecules which is a molecule that has small intermolecular forces due to symmetry of charge distribution.  The reading also talks about electronegativity which is the ability of an atom to attract electrons in a chemical bond.

Chapter 7 section 8

We have been working with lewis structures recently in our class.  This is a picture that shows the outer shell valence electrons.  It shows the electrons bonding and being formed.  We learned about single, double and triple bonds too.  A single bond is one pair of electrons that bond together.  A double bond is two pairs of lone electrons that form 2 bonds.  And a triple bond is three pairs of lone electrons that form together and form a triple bond.  Shared pair of electrons are called covalent bonds and lone pair of electrons are called non bonding electrons.  I find these to concepts to be very interesting