What dose it mean for a material to be brittle?

Answer explain why it is not possible to deduce a complete order of reactivity.

Sandy is building a small toy car. he wants to use a balloon to power the toy car. he fills a balloon with air and then attaches a straw to the balloon. he tapes the balloon-straw combination to the car and then releases the end of the balloon. the toy moves forward as the air from the balloon comes out the back of the straw. what can sandy do to make the toy car move faster? a) use less air in the balloon. b) blow up the balloon more. c) use a longer straw. d) use larger tires.

)a children’s liquid cold medicine has a density of 1.23 g/ml. if a child is to take 2.5 tsp in a dose, what is the mass in grams of this dose? (1 tsp = 5 ml)