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The People's Share · GED Science

Quiz 4 · Part I: The Scientist's Toolkit

Diagrams and Models

Cycles, flowcharts, cross-sections, and what the key is for

The Guide

Pictures that carry an argument

A diagram is not an illustration. It is a claim about how parts fit together, drawn instead of written, because the relationships would take three paragraphs in words and one glance on paper.

That means diagrams can be read wrong in a particular way: you can recognize the picture and still miss what it says. The remedy is to read the parts that are easy to skip — the key, the arrows, and the labels.

Four kinds you will meet

Cycle
Arrows in a loop. The material comes back around, so there is no true first step. You can enter anywhere.
Flowchart
Start at the top, answer each question, follow one branch. You cannot skip a step, and only one path leads to each ending.
Cross-section
A slice through something, as though it had been cut with a knife and you are looking at the cut face. Rock layers, a tooth, a leaf, the Earth.
Map or labeled drawing
Positions and parts, usually with a key telling you what each symbol means, and often a scale bar telling you how far the distances really are.

The key is not decoration. A symbol means whatever the key says it means, and nothing else. Read the key before you read the picture, the same way you read the axes before you read a graph. When a question seems to have two right answers, the key usually settles it.

Arrows carry the meaning. An arrow can mean flows into, becomes, leads to, or comes next. Which one it means depends on the diagram, and the diagram usually says. Follow arrows one at a time, in the direction they point. Reading a flowchart backward produces confident nonsense.

Lower is older. In rock layers that have not been tilted or turned over, each layer was laid down on top of the one below it. So the bottom layer formed first and the top layer formed last. This one fact answers a surprising number of questions, and it works for anything that piles up in order — sediment, tree rings, the papers on a desk.

Worked Examples

Two questions, worked through

Diagram The paper recycling cycle Four boxes in a loop, with arrows running clockwise: paper is made, then paper is used, then paper is collected, then pulp is recovered, then back to paper is made. Paper is made Paper is used Paper is collected Pulp is recovered
Example 1. Where does this cycle begin?

It does not. Every box has an arrow coming in and an arrow going out, which is what makes it a cycle rather than a list. Paper gets made, used, collected, pulped, and made again.

Example 2. According to the diagram, what happens immediately after paper is collected?

Find the box, then follow the one arrow leaving it. It points left, to "pulp is recovered." Not to "paper is made" — that is two steps away, and the diagram is specific about the order.

The Quiz

Ten questions

Answer all ten, then press the button at the bottom. Nothing is timed.

Diagram A — questions 1 to 3 The water cycle A landscape with an ocean on the left and a hill on the right. Stage 1 is an arrow rising from the ocean to a cloud. Stage 2 is at the cloud itself. Stage 3 is rain falling from the cloud onto the hill. Stage 4 is an arrow running down the hillside back into the ocean. 1 2 3 4

Water moving between the ocean, the air, and the land.

1.At which numbered stage does liquid water change into water vapor and rise into the air?

2.Which stage shows precipitation?

3.What does the looped shape of this diagram tell you?

Diagram B — questions 4 to 6 Flowchart for classifying a sample of matter Start with a sample of matter. First question: is it made of only one substance? If yes, it is a pure substance, and the next question is whether it can be broken into simpler substances by a chemical change — yes gives a compound, no gives an element. If no, it is a mixture, and the next question is whether it is the same all the way through — yes gives a solution, no gives a heterogeneous mixture. A sample of matter Is it made of only one substance? Yes No Pure substance Mixture Can it be broken into simpler substances by a chemical change? Is it the same all the way through? Yes No Yes No Solution Heterogeneous mixture Element Compound

4.According to the flowchart, what is the first question you must answer about any sample?

5.A sample is made of only one substance, and it can be broken into simpler substances by a chemical change. Following the flowchart, what is it?

6.Sand stirred into water is not made of one substance, and it is not the same all the way through. Following the flowchart, where does it end up?

Diagram C — questions 7 to 9 Cross-section of rock layers Five layers seen in a cut face. From top to bottom: A soil, B shale containing fossil shells, C sandstone, D limestone containing fossil coral, E conglomerate. A key at the right names each layer and the two fossil symbols. Cross-section of a road cut A B C D E KEY A — Soil B — Shale C — Sandstone D — Limestone E — Conglomerate Fossil shells Fossil coral

These layers have not been tilted or turned over.

7.According to the key, what is the third layer from the top made of?

8.Which layer formed first?

9.Fossil shells appear in layer B and fossil coral in layer D. Which fossils are older, and how can you tell?

Diagram D — question 10 Map of a park with four water sampling sites A park map showing a stream, a road running north to south, a marsh, and a wooded area. Four numbered sampling sites are marked. Sites 2 and 3 sit at the same height on the map, on either side of the road. A scale bar shows that a short bar represents 200 meters. Water sampling sites, Miller Creek Park 1 2 3 4 200 meters KEY Stream Road Marsh Woods Sampling site

10.Using the scale bar, about how far is it from Site 2 to Site 3?

Send this line to your teacher

The line records which questions you missed and which answer you chose. That is more useful to your teacher than the score, because it shows where a question went wrong. If a question felt unclear even though you got it right, add its number with a question mark — for example 5? — before you send it.

Score ______ / 10    Missed — write the question number and the letter you chose:
______________________________________________________________

The Key

Answers, and the trap in each one

1. A — Stage 1. The arrow rises off the ocean surface and goes up toward the cloud. Liquid becoming gas is evaporation, and it is the only stage that starts in the water and ends in the air. Follow the direction of the arrow. Stage 4 also touches the ocean, but its arrow points the other way, into the water rather than out of it. Direction is half the meaning of an arrow.
2. C — Stage 3. Precipitation is water falling out of the sky: the short downward arrows under the cloud. B sits at the cloud, where droplets are forming. Forming a cloud and falling out of one are different stages, and they are next to each other on purpose.
3. B — the same water goes around again and again. Every stage leads into the next and the last leads back to the first. That is what a closed loop of arrows means, and it is why the water on Earth is not used up. A treats the diagram as a list with a first step and a last one. The giveaway is the arrow from stage 4 back to the ocean, where stage 1 begins. There is no exit.
4. C — whether it is made of only one substance. It is the question the first arrow leads to. Everything else on the chart depends on how you answer it. A and B are the second-level questions, and each one is only reachable down one branch. If you start in the middle of a flowchart, you can produce an answer that the chart does not actually allow.
5. B — a compound. One substance, so take the Yes branch to "pure substance." Broken down by a chemical change, so take Yes again. That path ends at compound. A is what you get if you take the same path and answer the second question backward. Read each Yes and No label rather than guessing which side is which — the chart does not always put Yes on the same side.
6. D — heterogeneous mixture. Not one substance, so take No to "mixture." Not the same all the way through, so take No again. Sand and water separate visibly, which is exactly what that word describes. C is the other end of the same branch, and it is where salt water would land, since salt water looks the same throughout. The two endings differ by one answer.
7. B — sandstone. Count down from the top: soil, shale, sandstone. Then check the key to confirm that the third band is layer C. Counting from the wrong end gives limestone. When a question says "from the top," find the top first and put a finger on it.
8. C — layer E, at the bottom. Layers pile up in order, so the bottom one was there before anything was laid on top of it. The caption tells you these layers have not been tilted or turned over, which is what makes the rule safe to use here. D sounds appropriately cautious, and caution is usually a good instinct on this test. Here the diagram gives you exactly the condition you need, in the caption. Read the caption.
9. B — the coral, because layer D lies below layer B. The fossils are as old as the layer holding them. Layer D is deeper, so it was laid down earlier, so its fossils are older. A gets the relationship exactly backward, and it is the answer that feels right if you think of the top of a diagram as the beginning. On a page, the top comes first. In the ground, the bottom does.
10. C — about 400 meters. Sites 2 and 3 sit at the same height on the map, and the gap between them is about twice the length of the scale bar. Twice 200 is 400. B is what you get by reading the number off the scale bar without comparing it to anything, which is the same mistake as taking a percentage straight off a circle graph. The bar is a ruler, not an answer.

Your Score

What the number means

8 to 10Solid. Check topic 4 on your map and go on to Quiz 5.
6 or 7Close. Read the whole key, then take this again in a few days before you check the box.
5 or fewerWorth real time. Diagrams turn up in every section of the test, and the cycle and cross-section come back in Part IX.

Misses on 1, 2, or 7 mean a label or an arrow got read too quickly. Misses on 4, 5, or 6 mean the path through the flowchart went off track — try tracing it with a finger, out loud, one question at a time. Misses on 8 or 9 are about order in a cross-section, and the rule behind both is short enough to memorize: in undisturbed layers, lower is older.

The plate for this quiz

The gallery image is William Smith's geological map of England and Wales, published in 1815. Smith was a canal surveyor, not a gentleman scientist. Digging across the country he noticed that the rock layers appeared in the same order everywhere, and that each layer carried its own fossils — which meant a layer could be identified anywhere by what was buried in it. He spent years walking, and then hand-colored a map fifteen sheets wide, shading each layer where it reached the surface. It is the first geological map of a whole country, and it is still substantially correct.

Image to be placed at deployment. The map is out of copyright by age; high-resolution scans are held by several libraries and geological societies. Smith was, for a while, ruined by the cost of making it, and spent time in debtors' prison while a rival sold a cheaper copy. Recognition came later.