Name one chemical barrier the human body uses to defend itself against pathogens.
A student investigated the effect of different concentrations of a disinfectant on the survival of bacteria.
This is the method used:
Table 1 shows some of the results.
| Time in hours | Number of live bacteria at disinfectant concentration | |||
|---|---|---|---|---|
| 0% | 1% | 2% | 4% | |
| 0 | 320 | 320 | 320 | 325 |
| 12 | 280 | Y | 80 | 16 |
Name one chemical barrier the human body uses to defend itself against pathogens.
What fraction of the bacteria present at 0 hours for 2% disinfectant survived for 12 hours? Give your answer in its simplest form.
How many more bacteria were killed at 4% disinfectant than at 0% disinfectant in 12 hours? Complete the following steps:
A student calculated value Y in Table 1 to be 180. Suggest how the student calculated this value.