# Assessment Tips

11SCI - Chemical Reactions

2020

## Assessment Tips

1. Collect a paper from the front of the classroom
2. Name it
3. Quietly read through it while everyone else arrives

### How the Assessment Works

Day 1 Day 2 Day 3
Write predictions Continue whakamātaus Finish whakamātaus
Write word equations Complete write-up
Start whakamātaus Do excellence comparisons

### Achieved

For 2 out of the 6 reactions:

• Collecting information (observations) about a range of chemical reactions.
• Writing word equations to describe the chemical reactions.
• Classifying the chemical reactions.

### Merit

• Achieved + the following for 2 out of 6 reactions
• Explaining the classification of the chemical reactions.
• Completing symbol equations for the chemical reactions.

### Excellence

• Merit + the following for 2 out of the 6 reactions
• In depth discussion (may include justifying, elaborating, relating, analysing, links between the classification of the reactions, observations and equations).
• Completing balanced symbol equations for the chemical reactions.

## Making Observations

• Colour changes
• Gases given off
• Changes of states

• Relate your observations to the number of reactants
• Relate your observations to the number of products
• Relate the number of reactants/products to general reaction equations

### 3. Prediction

• Write a word equation
• You do not need to put states
• For precipitation reactions: state that a precipitate will form, and name it
• Include the solubility rule predicting the precipitate
• E.g. A precipitate of sodium hydroxide will form due to the solubility rule that says…

### 4. Results

• Describe the reactants
• State (l, g, s, aq)
• Colour (green, colourless)
• Shiny/matte
• Transparency (transparent, cloudy, opaque, translucent)
• Describe the products
• ^ As above
• Gas given off/bubbles formed
• Results of gas tests

### 5. Conclusion

• Word Equation
• Use a $$\rightarrow$$
• No states on the word equation
• State the charge of the ion if there are multiple options e.g. Iron (II)
• Be careful with sulfates/sulfides

### 5. Conclusion

• Symbol Equation
• Be careful with capitals: only the first letter is ever capitalised
• The number of each element/ion goes at the bottom
• Ensure that your formula are correct before you balance the equation!
• $$\xrightarrow{heat}$$ when using a Bunsen
• Balance the equation at the very end
• DO NOT WRITE STATES (you do not need them for excellence)
• DO NOT WRITE CHARGES (each compound should be neutral)

### 5. Conclusion

• Type of Reaction
• Simply state precipitation/displacement/combination/decomposition
• You do not need to give an equation with ABCDs, but you can use it in your reasons for choice of reaction below

### 5. Conclusion

• Reasons
• E.g. precipitation because a dark green precipitate was formed
• E.g. precipitation because the $$Fe^{2+}$$ and $$Na^{+}$$ ions swap their partners as expected $$AB + CD \longrightarrow AD + CB$$
• E.g. displacement because a silver deposit forms on the metal, indicating displacement
• E.g. displacement because (your metal) is more reactive than (other metal) indicating it would displace it
• E.g. combination because (describe substance) formed when combusted, indicating it combined with something in the air

### 5. Conclusion

• Comment
• Precipitation: relate to precipitate being formed as expected
• Relate to number of reactants that are elements (A) or compounds (AB)
• Relate to number of products that are element (C) or compounds (CD)
• By comparing these, the reaction will match only one of the general equations

#### Excellence

1. Those who want to learn how to do the excellence part of this assessment please shift to the front right of the classroom
2. Everyone else, shift to the left side of the classroom and use these notes (linked on Classroom) to continue to improve your practice assessment answers & work on your research task

### 6. Compare & Contrast

• Precipitation vs Displacement
• Give one or two similarities
• Give one or two differences
• Give a (balanced symbol) example equation from your six reactions, or from research, for each difference
• Link to solubility rules for precipitates
• Link to activity series for displacement

### 6. Compare & Contrast

• Combination vs Decomposition
• Give one or two similarities
• Give one or two differences
• Give a (balanced symbol) example equation from your six reactions, or from research, for each difference
• Compare energy needed to do decomposition/combination
• Compare difficulty of each reaction (combination usually needs more energy under more difficult conditions)

## What Do I Need To Know?

Types of Reactions Gas Tests Equations Observations
Combination Oxygen (glowing splint) Word equations Colours
Displacement Carbon dioxide (limewater) Ionic formula Gasses
Precipitation Hydrogen (pop) Symbol equations Solids formed
Decomposition Balancing equations Count #/type of reactants/products