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?
Esme has 56 g of copper. How many grams of zinc must be added to make brass, which is 70% copper by mass?
Read this first
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?
- PVC: its 5,000 bends at 25 °C show it is tough enough for a winter job too
- Polyethylene: its 6,000 bends at 25 °C is the top result of the three
- Natural rubber: it survives 3,500 bends at −20 °C, the most of the three
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
- Supported: low friction means the material is soft and weak throughout, so PTFE is weak
- Not supported: slipperiness is weak attraction to other surfaces, not weak bonds in PTFE
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 does not change with zinc, so the claim is baseless and wrong
- Overstated: hardness rises to 40% zinc, then falls at 50%, so more can be softer
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?
- Overstated: silver conducts about 6% better than copper at about 80 times the cost
- 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
Brass is harder than copper but conducts electricity worse. Which single structural idea explains both, Ren?
- Zinc atoms of a different size disturb the rows, blocking sliding layers and scattering electrons
- Zinc adds extra free electrons, which strengthens the bonds but slows the current somewhat overall
- Zinc atoms form covalent bonds with copper atoms, which removes the free electrons it had before
Rubber stiffens at −20 °C. Which structural idea explains it, Tala?
- The cross-links break in the cold, so the chains lock together
- The chains shrink to a shorter length, which makes the rubber stiff
- The chains have too little motion to uncoil, so the rubber stiffens
Spandex stretches to about five times its length and springs back. Which structure explains both, Zee?
- Cross-links melt when the fiber is stretched and re-form when it is released again
- Hard segments stretch while soft segments hold the chains in place, so the fiber returns afterward
- Soft coiled segments straighten when pulled; hard segments anchor the chains and pull them back