05. Observations

OUTCOMES:

> use results from fair tests to make comparisons

> draw conclusions

Today we will carry out a simple investigation. The aim of the investigation is to make observations about an experiment and to use these observations with the data to draw conclusions.

In the experiment you will have 6 text tubes filled with acids. You will have a sheet which tells you how much of what acid each test tube contains. When you are told to, in your group you will add a piece of magnesium to each test tube and observe what happens. You will write your observations down to help you draw conclusions later.

SAFETY FIRST!

Acids are harmful - Wear Safety Glasses

Here is a video of what to do to start.

And here is a video of what to look for.

Based on your observations, write the answers to these questions in your science book under the heading: Drawing conclusions

• 1. Which test tube (A, B, C, D, E or F) do you think contained the strongest acid?

  2. WHY?

  3. Which test tube (A, B, C, D, E or F) do you think contained the weakest acid?

  4. WHY?

  5. Does the type of acid affect how quickly it reacts with the magnesium?

  6. What observations did you make that support your answer?

  7. Here is a diagram that summarises the experiment, it should help you answer the last few questions.

• 1. Choose two or more of the experiments A–F that would allow you to find out the answers to the following questions. Remember that you need to do fair tests.

a How does the volume of acid affect the amount of bubbles?

b How does the concentration of acid affect the amount of bubbles?

c Is ethanoic acid more hazardous than hydrochloric acid?

6. a Which experiment cannot be used as a fair comparison with any other test?

b Why not?

c Suggest how you could change the conditions in this tube to make it a fair comparison.

d What question would you then have evidence for?

7. Are the following conclusions true or false? Explain your answers using evidence from the table.

a The larger the volume of acid, the more bubbles are produced.

b A higher concentration acid is more hazardous.