Parents Guide for Unit 38
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Below are notes on the main points of each assignment.
We are reading an excerpt of Dalton's own writings, which use nineteenth century terms, so students may need to spend some time reading this section carefully. I've included a number of specific questions with the reading assignment. Students do not need to write down the answers but they should be able to figure them out from the reading and be ready to discuss them in chat.
Please discuss with your student the study questions at the end of the web lecture.
Chemical reactions employ all of Dalton's three rules: they recognize that molecules of a given substance have specific combinations of individual atoms (law of constant composition), that these can be rearranged in different ratios (law of multiple proportions), and that in a chemical reaction, atoms cannot be created or destroyed (conservation of mass). We use these rules to balance equations, making sure that we have the same number of atoms of each element in the products (resulting molecules) as we did in the initial reactants.
Chemical reactions only take place if sufficient energy is available to start the reaction (activation energy). If the reaction itself releases sufficient energy, the released energy from one recombination of molecules can become the activation energy to start a reaction in another set of reactants, and the reaction becomes "spontaneous" with all available reactants participating. If the reaction does not produce enough energy to overcome the activation energy barrier, or if the reaction absorbs energy (endergonic reaction), then the reaction will stop.
The exercise questions identify key concepts students should understand as a result of the reading and discussion. Make sure that the student reads and attempts to answer the exercises before chat, so that he can identify questions that need to be discussed in chat.
Our Chat discussion will concentrate on Dalton's laws and the essential concept of proportion in chemical reactions.
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