# Unit 5 Counting matter. Challenge Question (first correct answer gets a sticker) The plastic vial on the front desk contains a certain number of beads.

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Unit 5 Counting matter

Challenge Question (first correct answer gets a sticker) The plastic vial on the front desk contains a certain number of beads. Without counting, estimate the number of beads that you see. How many additional identically filled vials could you fill from the plastic beaker? Use significant figures (don’t round to whole number vials. Suppose that you over-estimated the number of beads in the vial. The correct number of beads in a vial is only 90% of your original estimate. How does this affect your answer to the question in red?

Wrap up from relative mass activity Working in assigned pairs, review your relative mass activity to answer the following. List units of mass which appear in your calculations List units of amount which appear in your calculations List conversion factors (ratios) between mass and amount, which appear in your calculations Have you considered volume in any of these problems? List common volume units, whether they’ve appeared in this problem set or not.

Evaluating Dalton’s theory Working in assigned pairs, prepare a white board to answer the following question: Dalton observed that many metals react with oxygen to form more than one type of compound (multiple proportions). He assumed that the simplest known oxide of every element was a 1:1 ratio, and used this to calculate relative atomic masses. Evaluate Dalton’s assumption. Cite evidence to show where it was correct and cite evidence to show where it was incorrect. In cases where Dalton’s assumption was incorrect, draw particle diagrams to compare the correct and incorrect interpretation of compound formation and to show why Dalton was mislead.

Observe the reaction between Zinc and hydrochloric acid (HCl) Working with your assigned partner, draw a particle diagram to describe your observations. Working with your assigned partner, propose further experiments to isolate and characterize the products, both quantitatively and qualitatively.

Design an Experiment to determine the empirical formula of the compound(s) formed in the reaction between zinc and hydrochloric acid. You must write a typed experimental design for the next class period. Each individual student must write their design independently You will not be allowed to begin the lab work next class period until you have a suitably detailed plan for how you are going to meet this objective Review everything we have discussed about experimental design writing from earlier in the year. Must include enough detail that it could be repeatable by another student. It must include a plan for analyzing and interpreting the data along with the procedure for collecting data. Include a summary of any safety concerns, especially with HCl

Evaluate an experimental design Start by stating your objective Every step in your design should relate back to that objective, in the most direct and accurate way possible Design does not include the actual data Design must include an explanation of how the measured results will be analyzed to meet the objective. Include enough procedural detail that another student could repeat the experiment with similar results. However, the experimental design is not simply a “procedure”. It should not be a bullet point list of steps and should not include trivial steps that a student of general chemistry would already know to follow. Science writing should not include personal pronouns.

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