Brainlies 1. which statement is true about oxygen and rocks? both are mixtures. both are pure substances. oxygen is a mixture and a rock is a pure substance. oxygen is a pure substance and rocks are mixtures. 2. it takes 1 minute for a certain amount of potassium phosphate (kh2po4) to dissolve in 100 grams of water at 50 °c. which of the following will most likely happen if the same sample of potassium phosphate is dissolved in 100 grams of water at 20 °c? the sample will dissolve in exactly 1 minute. the sample will dissolve in more than 1 minute. the collision between particles of the sample will increase. the collision between particles of the sample will remain constant.