「increase」と「become」の違い

Somebody was asking me about the difference between these two. We were talking about how people deal with cold weather.

× Cold weather becomes the demand for hot water bottles.
○ Cold weather increases the demand for hot water bottles.
○ Demand for hot water bottles becomes greater in cold weather.
○ Normally low demand becomes high demand in cold weather.

• hot water bottle 湯たんぽ (definition from Weblio)

The key point to remember is that "increase" means a number is growing, while "become" can talk about any change. We can talk about "demand" as a number, so we can use "increase".

• increase (数量・程度などが)ふえる，増加する (definition from Weblio)
• become〈…に〉なる (definition from Weblio)

Another example we talked about was related to North Korea. We were discussing some possibilities, and these sentences came up:

× The crisis will increase more severe. <- a "crisis" is not a number
○ The crisis will become more severe.
○ A less-serious situation becomes a severe crisis.
○ The severity of the crisis will increase. <- "severity" can be ranked on a numeric scale

• crisis 危機，決定的段階，重大局面 (definition from Weblio)
• severe ひどい，猛烈な (definition from Weblio)
• severity 重症度 (definition from Weblio)

I have been practicing making this five-spice tofu for a few weeks. It is becoming better each time I make it. The number of dishes that I can make is increasing, but I think I still can't become a restaurant owner. Not yet, anyway.