Why a material's molecules decide what it can do
Grade 10 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
Ari has 74 g of silver. How many grams of copper must be added to make sterling silver, which is 92.5% silver by mass?
Bo has 66 g of copper. How many grams of tin must be added to make bronze, which is 88% copper by mass?
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Three frame metals (typical values, rounded)
material strength (MPa) density (g/cm³) structural steel 400 7.85 aluminum alloy 310 2.70 titanium alloy 950 4.43 A frame must be as strong as possible for its mass. Which comparison is best supported, Jun?
- Titanium gives the most strength per density: about 214, against 115 and 51
- Aluminum is the clear choice, since it has the lowest density of the three metals listed
- Titanium and steel tie, since both are stronger than aluminum in the strength column
Card
Cookware metals (rounded). Thermal conductivity in W/(m·K): copper 401, aluminum 237, stainless steel 16. Copper reacts with acidic foods; stainless steel does not.
A pan must spread heat evenly and be safe with acidic foods. Which design uses the card best, Kira?
- A copper core for even heat, lined with stainless steel that resists acid
- Solid stainless steel, since it does not react with the acid in tomato sauce
- Solid copper, since it conducts heat better than the other two metals do
Wire coating flex test (example data)
coating bends to crack at 25 °C bends to crack at −20 °C PVC 5000 200 natural rubber 4000 3500 polyethylene 6000 1500 A wire will hang outdoors where winter nights reach −20 °C. Which coating does the data favor, Luz?
- Natural rubber: it survives 3,500 bends at −20 °C, the most of the three
- Polyethylene: its 6,000 bends at 25 °C is the top result of the three
- PVC: its 5,000 bends at 25 °C show it is tough enough for a winter job too
A student says PTFE is slippery, so it must be a weak material. Which reply is best, Milo?
- Supported: polymers are weak materials, and a slippery coating like PTFE shows it clearly
- Not supported: slipperiness is weak attraction to other surfaces, not weak bonds in PTFE
- Supported: low friction means the material is soft and weak throughout, so PTFE is weak
Brass hardness and zinc (example data)
zinc (%) hardness 0 50 10 70 20 85 30 95 40 110 50 80 A student says more zinc always makes brass harder. Which reply fits the table, Noah?
- Supported: hardness rose at each step from 0% to 40% zinc, so the pattern holds
- Overstated: hardness rises to 40% zinc, then falls at 50%, so more can be softer
- Overstated: hardness does not change with zinc, so the claim is baseless and wrong
Four conductors (rounded values; costs are examples)
metal conductivity (10^6 S/m) cost compared with copper silver 63.0 80 times copper 59.6 1 time gold 41.0 6000 times aluminum 37.7 0.3 times A student says the best conductor is always the best choice for house wiring. Which reply fits the table, Pia?
- Supported: the highest conductivity, 63.0, makes silver the right wire for house wiring
- Supported: gold resists corrosion well, so gold should be chosen for house wires
- Overstated: silver conducts about 6% better than copper at about 80 times the cost
Brass is harder than copper but conducts electricity worse. Which single structural idea explains both, Ren?
- Zinc adds extra free electrons, which strengthens the bonds but slows the current somewhat overall
- Zinc atoms of a different size disturb the rows, blocking sliding layers and scattering electrons
- Zinc atoms form covalent bonds with copper atoms, which removes the free electrons it had before
Spandex stretches to about five times its length and springs back. Which structure explains both, Zee?
- Soft coiled segments straighten when pulled; hard segments anchor the chains and pull them back
- Hard segments stretch while soft segments hold the chains in place, so the fiber returns afterward
- Cross-links melt when the fiber is stretched and re-form when it is released again