Activity 1. Shaping up—surface area to volume ratio and diffusion

In this activity, you will use a simulation to investigate the effect of surface area to volume ratio on the diffusion of substances and consider the importance of this on the efficient exchange of materials for organisms. The shapes of organisms will be simulated by blocks of agar jelly. The jelly is a pink colour due to the presence of sodium hydroxide (a base) and phenolphthalein indicator. Phenolphthalein is colourless in acid. When the blocks are placed in an acid solution, the acid diffuses into the jelly, causing a colour change from pink to clear. The time taken for a block to totally decolourise is a measure of the rate of diffusion of acid into the jelly.

 60 minutes

Elements always combine in a definite mass ratio to form compounds. In this experiment, magnesium metal is heated in oxygen to form the compound magnesium oxide. By finding the mass of the original magnesium and that of the magnesium oxide, the percentage of magnesium in magnesium oxide can be calculated. The mole ratio of magnesium to oxygen can also be determined so that the empirical formula can be derived. 

 100 minutes

Carbon dioxide is one example of a metabolic waste produced by cells. It is carried to the lungs via the bloodstream, where it is removed from the body during exhalation. Hydrogen peroxide (H2O2) is another waste product of cell metabolism. It is a potentially harmful chemical and must be removed immediately. The enzyme catalase operates in cells to continually break down hydrogen peroxide into harmless products. 

In this primary data investigation, you will investigate the potential for water loss from upper and lower surfaces of leaves of different kinds of plants and then take steps to verify your experimental outcomes. You will make inferences about the relationship between a plant’s stomatal distribution and its potential water loss.

 In this investigation, you will study the effect of different kinds of antibiotics on the growth of bacteria using Mastrings or Multodiscs. These are commercially produced discs impregnated with a variety of antibiotic substances. Each satellite on the Mastring contains a different antibiotic that is identified by either a colour or a letter code or both.