When liquids change into a solid, it is called freezing. This happens when energy is removed from the liquid. When liquids change into a gas, it is called boiling. This happens when energy is added to the liquid.
Signs of a chemical change include: color change (two clear liquids producing a yellow liquid), phase change (two liquids producing a solid precipitate or a gas), temperature change (two liquids combining and cooling the solution down or heating it up).
mixtures can be formed by physically putting two or more substances together. Mixtures can be formed between solids and liquids, solids and solids, liquids and liquids, solids and gas, liquids and gas, gas and gas