Why does platinum metal make a good catalytic surface for reactant molecules? it causes reactant molecules to be less reactive. it strengthens bonds between reactant molecules. it prevents products from breaking away from the surface. it holds reactant molecules in a good position for them to react.

It holds reactant molecules in a good position for them to react.

Explanation: Catalysts are substances which increases the rate of reaction by taking the reaction through a different route which involves lower activation energy and do not get itself consumed.

Platinum metal has active sites on its surface and thus more reactant molecules can be brought into closer contact with one another. When more molecules can be brought closer together, there are better chance of an effective collision , i.e. more reactants can be converted to products. Thus the rate of reaction increases and thus platinum act as good catalytic surface.

a. a primary source combines several different accounts of an event. b. a primary source generally benefits from having been written after an event.

explanation:

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied