At 298 k and 1 atm, bromine is a liquid with a high vapor pressure, whereas chlorine is a gas. this provides evidence that, under these conditions, the forces among br2 molecules are than those among cl2 molecules

Explanation:

In liquids, the molecules are held by less strong intermolecular forces of attraction as compared to solids. Due to which they are able to slide past each other. Hence, they have medium kinetic energy.

In gases, the molecules are held by weak Vander waal forces. Hence, they have high kinetic energy due to which they move rapidly from one place to another leading to more number of collisions.

So, when at 298 K and 1 atm exists in liquid state and exists as a gas then it means there occurs strong force of attraction between the molecules of due to which it exists in liquid form.

Thus, we can conclude that at 298 K and 1 atm, bromine is a liquid with a high vapor pressure, whereas chlorine is a gas. This provides evidence that, under these conditions, the forces among molecules are greater than those among molecules.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds