How many variables should be manipulated in a correctly performed scientific experiment?

There should be one manipulated variable in a science experiment to be consistent. One purposefully manipulated (Independent variable), something will change(dependent variable) because of that and something(s) will stay the same (constant variable)

There should only be 1...bc if u have more than 1 it would mess up the whole project

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.