The method and the results are on the rates of reaction lab. Do the analysis yourself first, then check the answers below.
Quick answer: The rate of reaction is how quickly reactants are used up or products form, measured as amount per unit time. These answers go with the Chemistry 9-10 lab on rates of reaction: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
Use the sample data to check your working. The exact times from your own group will differ, but the times should shorten steadily as the water gets hotter and the rate should grow by about 1.5 to 2 times for each 10 °C rise.
Level: Chemistry grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: HS-PS1-5
The rate rises as the temperature rises, and the line curves upwards, getting steeper at higher temperature. An upward curve.
Question 3 Factor per ten degrees
Factor from 20 °C to 40 °C = 40.0 ÷ 12.5 = 3.2. That covers two rises of 10 °C, so the average factor per 10 °C is √3.2 = 1.8. This is slightly lower than 2, so the doubling rule is only approximate. 3.2 overall; about 1.8 per 10 °C.
Question 4 Explain with collisions
At higher temperatures the particles have more energy and move faster, so they collide more often. A much larger fraction of collisions has at least the activation energy, so more collisions succeed and the rate rises. More successful collisions.
Question 5 Control variables
Volume of water (200 cm³), the type and mass of tablet, and whether it is whole or crushed. Each of these changes the number of particles or the surface area exposed, so it would change the rate and make the comparison unfair. Volume, tablet and size.
Question 6 Timing uncertainty
9 s: 1 ÷ 9 × 100 = 11%. 190 s: 1 ÷ 190 × 100 = 0.53%. The 9 s result is less reliable because reaction time of the person is a much larger fraction of the time. 11% and 0.5%.
Question 7 Improvements
The rate of reaction increases as temperature increases, by roughly 1.8 times for each 10 °C rise here. Improvements: repeat each temperature three times and take a mean; keep the water at constant temperature with a water bath, or use a data logger to detect when fizzing stops. Higher temperature gives a higher rate.
