# Author Archives: evantoh

## The project to remove 88,000 tons of plastic from the Pacific has begun

Glad to see such projects which benefit the environment.

## Disappearing test tube

## Watch “CeramicSpeed DrivEN 99% Efficient Drive Shaft // Chain Free Bike // Eurobike 2018” on YouTube

## Another P1V1 = P2V2 question

Solution: Option C

## When to use the concept PV = constant and P1V1 = P2V2 to solve?

When **temperature is constant** (for o-level), when a __fixed mass of gas (fixed number of air molecules)__ is __compressed__ in a closed system (e.g. piston), the __volume V decreases__ and __pressure P increases__, and vice versa.

But when you multiply pressure and volume, PV, it is always a constant.

**PV = constant**

Hence we can always equate the PV of the first scenario = to the PV of the second scenario, provided there is no addition or removal of air molecules from the system.

Hence, you have **P1V1 = P2V2**

The followings are 4 different questions which require this concept to solve. Do revise them.

**Solutions: Option D** (refer to the worked solutions below)

**Solutions: Option D**

**Solutions: A**

4)

**Solutions:**

5)

**Solution: Option C**