Match the following.

1. to bend
-
opaque
-
2. not allowing light to pass through
-
refract
-
3. only partially clear
-

translucent
4. clear
transparent

1. to bend ==>  refract

2. not allowing light to pass through   ==>  opaque

3. only partially clear ==> translucent  

4. clear  ==>  transparent

Explanation:

1. to bend ==>  refract

When a substance (like water) or a surface (like a mirror) changes the direction of the light, it refracts it.

2. not allowing light to pass through   ==>  opaque

Usually a solid but also a thick/dark liquid can be an opaque barrier preventing the passage of light.

3. only partially clear ==> translucent  

Think about a white plastic or a film-coated glass pane, they will let you see there's light on the other side, but not letting it pass through completely.

4. clear  ==>  transparent

Think like a window or a anything similar that allows the light to pass through without any significant obstruction.

the reaction mixture contains some ammonia, plus a lot of unreacted nitrogen and hydrogen. the mixture is cooled and compressed, causing the ammonia gas to condense into a liquid. the liquefied ammonia is separated and removed. the unreacted nitrogen and hydrogen are then recycled back into the reactor .