Which model below represents a pure substance?

question 1 options:

neither figure 1 nor figure 2 are pure substances.

figure 1, because it is a compound.

both figure 1 and figure 2 are pure substances.

figure 2, because it is a compound

In which situation is the acceleration of a car negative? question 5 options: a)the velocity of a car was 75 km/hr over 4 hours. b)the velocity of a car reduced from 50 km/hr over one minute. c)the velocity of a car increased from 40 km.h to 75 km/h over 15 minutes. d)the velocity of a car was 45 km/hr at 2: 00pm and at 4: 00pm its velocity was 85 km/ht.