2. Moving Water Diffusion – The process by which materials move from an area of higher concentration to an area of lower concentration in order to reach equilibrium. This is one of the processes that a cell uses in order to take in food and other nutrients necessary for the cell’s survival, as well as a means to release waste products from the cell.

3. Moving Water Homeostasis – Through homeostasis, the cell maintains a balanced environment inside and outside the cell. When homeostasis is reached there is no net movement of water in or out of the cell.

4. Moving Water Osmosis – the movement of water across a membrane from an area of high concentration to an area of low concentration.

5. Moving Water Semi-Permeable Cell Membrane – The semi- permeable cell membrane is the outer membrane of the cell that regulates materials that go into and out of the cell. There are three ways a cell moves material across its membrane. They are active transport, passive transport and diffusion. The first two methods require energy, while diffusion does not. Our concern today is with the process of diffusion and how materials are moved across the membrane in this way.

6. Surface Area The measurement of the surface of a three dimensional solid. The area of a cube can be calculated by multiplying together the lengths of two adjacent sides and then multiplying that product by 6 which is the number of sides. Surface area is measured in square units.

7. Surface Area Example If S = 3 cm, then to calculate the surface area of the cube you first substitute 3 cm for S and then solve the formula for surface area. Surface Area = 6(3 cm) 2 Surface Area = 6(3 cm)(3 cm) Surface Area = 6(9 cm 2 ) Surface Area = 54 cm 2 S Surface Area = 6(S) 2, where S = the length of a side of the cube.

8. Volume The size of a three-dimensional space enclosed within or occupied by an object. Volume is measured in cubic units.

9. Volume Example If S = 5 cm, then use the formula Volume = S 3 to calculate the volume. Volume = S 3 Volume = (5 cm) 3 Volume = (5 cm)(5 cm)(5 cm) Volume = 125 cm 3 To calculate the volume of the cube you multiply the length, height, and width together. In the case of the cube, these measurements are all equal. s s s

10. Direct Variation When two variables are related in such a way that as one variable increases so does the other or as one variable decreases so does the other.

11. Inverse Variation When two variables are related in such a way that as one variable increases in value the other decreases in value and vice versa.