Monitoring and controlling chemical reactions Study Guide

Higher: Concentration is a fundamental concept in chemistry that quantifies the amount of solute present in a given volume of solution. It is typically expressed in grams per decimetre cubed (g/dm³). To fully grasp concentration, it's essential to understand the relationship between the mass of the solute and the total volume of the solution. The solute is the substance being dissolved, while the solvent is the substance doing the dissolving (often water). The solution is the homogeneous mixture formed when the solute dissolves in the solvent. A higher mass of solute dissolved in the same volume of solution will result in a higher concentration. Conversely, if the same mass of solute is dissolved in a larger volume of solution, the concentration will be lower because the solute particles are more spread out. The formula linking these quantities is: Concentration (g/dm³) = Mass of solute (g) / Volume of solution (dm³). This relationship allows for calculations to determine any one of these three variables if the other two are known. For example, if you know the desired concentration and the required volume of solution, you can calculate the mass of solute needed. Similarly, if you know the mass of solute and the concentration, you can find the volume of solution. It's crucial to ensure consistent units, particularly converting volumes from cm³ to dm³ (1 dm³ = 1000 cm³) before performing calculations to avoid errors in the final concentration value.

Enzymes are protein molecules that perform a vital role as catalysts in living organisms. A catalyst is a substance that increases the rate of a chemical reaction without undergoing a permanent chemical change itself. In biological systems, enzymes are highly specific, meaning each enzyme typically catalyses only one or a few very similar reactions. They work by providing an alternative reaction pathway with a lower activation energy, which is the minimum energy required for a chemical reaction to occur. This enables biological reactions to proceed at speeds necessary to sustain life at body temperature, where reaction rates would otherwise be too slow. Without enzymes, many metabolic processes, such as digestion, respiration, and synthesis of new molecules, would not be possible or would happen too slowly to sustain life. Enzymes are not used up in the reactions they catalyse, allowing them to be reused multiple times. They are crucial for maintaining the delicate balance of chemical reactions within cells and organisms.