when the combustion engine was invented it had many positive effects on society, but years later it has been discovered that the burning of oil and coal has one major negative effect on the environment. what is that negative effect?

Several negative effects of the combustion engine are : 
- It Defects air quality
- It uses nonrenewable Resources ( which means that one day the resource will be extinct)
- It causes holes in the ozone which will lead to increase in earth temperature

hope this helps

The RATE of producing, moving, converting, or using energy is "power".
The unit is "watt".  1 watt means 1 joule of energy per second.