A mixture is a system that is made up of two or more substances which are not combined chemically. A pure substance is a system that only has one substance. The following are classified as: 1.water : pure substance <span>2.blood : mixture</span> <span>3.the oceans : mixture</span> <span>4.iron : pure substance 5.brass : mixture</span> <span>6.uranium : pure substance</span> <span>7.wine : mixture</span> <span>8.leather : mixture</span> <span>9.table salt (NaCl) : pure substance</span>
Carbon forms compounds that make up about 18 percent of all the matter in living things. The processes by which organisms consume carbon and return it to their surroundings constitute the carbon cycle.
