How can a small spark start a huge explosion? using electric forces and molecules

Molten iron fills a mould, which has a volume of 200 cm cubed. calculate the volume when the iron cools and solidifies.

What are two different ways you could find the value of a? explain these methods.

Which of the following is not a means to accelerating? question 4 options: a)increase speed b)remain still c)decrease speed d)change direction