Which phrase best describes a chemical reaction? a. mixing two substances b. the combustion of a substance c. forming or breaking bonds d. the decomposition of particles

Answer is: C. forming or breaking bonds.

In a chemical reaction, chemical bonds are forming and breaking and this cause the transformation of one group of chemical substances to another

For example synthesis of water from its elements: 2H₂ + O₂ → 2H₂O, nonpolar bonds between hydrogen and oxygen atoms are breaking and new polar bonds are forming between hydrogen and oxygen in molecule of water.

(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

the objects have the same charge.