How are mixtures different than pure substances?

Question 5 options:

Mixtures contain only one type of atom.

Mixtures can be separated physically.

Mixtures are less dense than pure substances.

Mixtures have lower boiling points.

Harvey mixes two liquids. which observation of the new mixture most likely indicates a precipitate is forming?

Three alkali metals in group 1 are a. calcium, strontium, barium b. boron, aluminum, gallium c. sodium, potassium, rubidium d. fluorine, iodine, chlorine

Two metal blocks that have slightly different temperatures are placed next to one another. after five minutes, they both have lower but equal temperatures. according to the law of conservation of energy, what  most likelyhappened? energy was created inside the blocks. energy was destroyed inside the blocks. energy was absorbed into the blocks from outside the system. energy was transferred from the warmer block to the cooler block.