5. : Dimension - Dimension is a property of a shape, and tells us if the shape has depth. A school playground is 3-D, but a drawing you make on a flat piece of paper is 2-D. Length - The edges of a shape have a certain length. The length of the edges of a shape is what gives it a certain size, and can be measured. The faces of both 2-D and 3-D shapes have edges of certain length. You experience this property when you measure the edge of something with a ruler. Area - The amount of space the surface of one face takes up is called the area. If you put a shape on a piece of graph paper, the number of squares the face covers is the area. The area of a shape can be measured in square centimeters (cm2) and is a property of both 2-D and 3-D shapes. You have experience with this property when you notice that your friend got a bigger slice of pizza than you did. Surface Area - If you add together all of the areas from the faces of a 3-D shape, then the total is the surface area. It is the total amount of space needed to cover the outer surface of the shape. This is a property of 3-D shapes, and you might have noticed it when you've tried to figure out how much wrapping paper to use to wrap a present. Volume - The amount of space that a 3-D shape takes up is called volume. Volume can either be filled with a solid (like the chocolate in a chocolate bar), a liquid (like the amount of milk in a glass), or a gas (like the amount of air in an empty box). Volume is a property of 3-D, but not 2-D, objects and can be measured in cubic centimeters (cm3) or in milliliters (mL). In fact, one cubic centimeter of water is also 1 milliliter of water! You experience volume when you help make cookies and measure out the ingredients with measuring cups