Good morning, class. Before we start, I am going to distribute Activity Sheet 1.

Teacher has already displayed all the items found in Activity Sheet 1 on the teacher’s table.

Students, please come and examine these items on my table carefully. I want you to classify them into elements, compounds and mixtures by completing the task as required in Activity Sheet 1.

Students are given 5 –10 minutes to complete the activity.

Teacher displays the correct answers on a transparency.

Please check your answers. How many of you have got all the answers correct?

Teacher waits for students’ responses.

Excellent.
How do you classify the 20 items that were displayed?
Do you know what are elements, compounds and mixtures?
An element is a substance which cannot be broken down into two or more simpler substances by chemical methods.
Can any of you give examples of elements?

Teacher guides students until they get the following answers: Sulphur, iron, aluminium, charcoal, gold and silver.

Very good.

A compound is a substance which consists of two or more elements chemically combined together. Can any of you name some examples?

Teacher guides students until they get the following answers: Salt, sand, marble, wood, sugar, rice, carbon dioxide, plastic spoon and glass.

Good!

A mixture consists of two or more substances which are not joined together chemically. Can you give some examples?

Teacher guides students until they get the following answers: Diluted acid, syrup, petrol, air, coffee and crude oil.

You are given four petri dishes containing four different substances:
Petri dish A contains sulphur powder (yellow)
Petri dish B contains iron filings (black)
Petri dish C contains salt (white) and
Petri dish D contains sand (brown)

Follow the instructions in Activity Sheet 2a, 2b and 3. Carry out the activities in groups and write your observations in the tables given.

Teacher facilitates the class activities.

After the students have completed activities 2a, 2b and 3, teacher discusses the results.

Leader of group 1, please come out and present your results.

While the group representatives present their results, teacher writes the results of each group on the board (for comparison purposes). After all the groups have presented their results, teacher continues the discussions.

Now look at the board. Are there any differences between the results presented by all the groups?

Teacher waits for students’ responses.
From the results from Activity 2, iron filings can be separated from the mixture of sulphur powder and iron filings using a bar magnet before heating the mixture. After they are heated, they become a new subtance which is called a compound. This new substance cannot be separated by a magnet. Why is it so?

Teacher guides students until they get the following answer:
When a mixture of sulphur powder and iron fillings is heated, a chemical reaction has taken place. The iron filings and sulphur powder are combined together chemically and formed a
new substance with properties totally different from their original substances.

Very good. So now you know one difference between a compound and a mixture.

Let us look at the results of Activity 3. What is the purpose of this activity?

Teacher guides students until they get the following answer: To separate the components of a mixture.

Excellent! This is another method to separate the components of a mixture and it is called filtration. So you have learnt two ways of separating the components of a mixture. What are the two ways?

Teacher guides students until they get the following answers:
1. separation by magnet.
2. separation by filtration.

Let us look at the questions in Activity Sheet 2. Let us go through it together.

Can you identify the original colour of iron filing and sulphur powder?

Teacher waits and listens to students’ responses.

Does the color of the substances remain the same after heating?

Teacher waits and listens to students’ responses.

Why is there a change in colour?

Teacher waits and listens to students’ responses.

Can the iron filings and sulphur powder be separated using bar magnet:
a) before heating?
b) after heating?
Teacher waits and listens to students’ responses.

What substances can be attracted by a bar magnet?

Teacher waits and listens to students’ responses.

Name the new substance formed after heating?

Teacher waits and listens to students’ responses.

What is the conclusion of this activity?

Teacher waits and listens to students’ responses.

Let us now look at the questions in Activity Sheet 3b.

Why do we need to use filter paper to separate the mixture?

Teacher waits and listens to students’ responses.

What is the product left in the evaporating dish?

Teacher waits and listens to students’ responses.

What happens to the water in the filtrate?

Teacher waits and listens to students’ responses.

After all the activities you have done today, give other examples of a compound and mixture?

Teacher waits and listens to students’ responses.

State the differences between compounds and mixtures?

Teacher waits and listens to students’ responses.

Did you enjoy today’s science lesson?

Teacher waits and listens to students’ responses.

For your home work, please show the differences between mixture and compound in a table and also visit the web site below:

http:richthornley.tripod.com/ehemistry/onlinehomework/
elemcompmixtures/online.ner.htm

Those who do not have computers at home, can use the facilities in the school computer laboratory.

Teacher distributes “ 3 in 1” coffee mixture to each student.

Class, now each of you are given “3 in 1” coffee mixture.
Try to separate it at home.

Tell me the result in the next lesson.
Before you leave the laboratory, make sure you clean your table and return all the apparatus to their respective places.

Thank you. See you all tomorrow