Introduction to the Lesson-Note-Third-Term-Week-2-3-Basic-Science-Primary-5
This lesson introduces the pupils to elementary chemistry – the concepts of atom, chemical elements and then the two key chemicals – acids and bases. Well presented, the pupils will starts to develop some basic skills in scientific method – the act of questioning and providing logical or scientific answers to questions.
To Basic Science and Technology (BST) Teachers
Basic-Science-Technologies teachers must understand that this is a practical subject. Hence, the success of its delivery stretches beyond the cognitive objectives. A BST teacher is a demonstrator, mind influencer and a motivator that inspires his/her student to DO. As a result, s/he delivers the class by demonstration and motivation while measuring his/her performance by what the pupils are able TO DO at the end of the lesson.
Acids and bases – Meaning, types, examples, properties and uses of acids and bases
By the time this lesson end, the pupils should have attained the following objectives:
- Define both acid and base;
- list the types and examples of acids/bases;
- mention some physical properties of acid and base;
- use the properties to differentiate between acids and bases; and finally
- state some uses of acids and bases
- Develop some safety consciousness in handling unknown substances
- Grow awareness of the danger of “rampant consumption” of [unripe] fruits – which is common in this part of the country.
- Develop increased curiosity at changes in the environment
- the pupils should be able to apply scientific method in finding scientific answers to question
- Carry out acid/base identification experiment on a number of substances.
The teacher presents the lesson in order of steps as given below:
Step 1: Introduction: the concept of acids and bases
To introduce the lesson, the teacher goes walks into the class with a dry cell and liquid soap: say dettol. Thereafter, the teacher calls the attention of the pupils and informs them that s/he (the teacher) is hungry and thirsty. Following, the teacher demands the pupils if s/he may eat the dry cell or drink the liquid. This should obviously induce an echoing no! To this the teacher asks why s/he may not eat/drink the specimens. The teacher receives as many answer as possible. Tendencies are that the pupils will say because the specimens harm or kill. In response to this, the teacher asks what makes the specimens harmful. Proximate answer will be that “because the specimens are chemicals”.
Why dry cell and liquid soap are harmful
Upon receiving this or similar response, the teacher affirms the harmfulness of the specimen. S/he also explains that the specimens are harmful because they contain chemicals. Thereafter, the teacher explains that they shall, in the topic of the week, learn more about two of the most common chemicals – acid and bases.
Afterwards, the teacher writes the topic on the board then asks who among the pupils had seen or heard about either of acid or base in the past. If there is any, the teacher engages the pupil(s) in a short interaction then asks them what they would say acid/base is. After the ensuing discussion or if none of the pupils indicated to have heard of acid or base, the teacher explains that acids and bases are chemicals which they are going to learn about. After that, the teacher lists and explains the lesson objectives.
Sources of acids and bases
Succeeding the explanation of the lesson objectives, the teacher briefly notes that acids and bases may be of natural or artificial (that is, man-made or synthetic) sources. Natural acids are acids that are present in nature – animals and things that are not made by man such as trees and rocks.
The teacher stresses on with the synthetic-ability of acids. S/he explains that scientists are able to make acids and bases in the laboratory. This should raise question such as “how are the scientist able to make acids?”
How do scientists make acids and bases in the laboratory?
In response to the question, the teacher explains that scientists are curious people – people that like to learn about the things around them and as such who ask a lot of questions. The teacher continues that scientists even have a special way of answering their questions. And that this special way of answering questions is known as scientific method. In conclusion of the explanation, the teacher explains that through this scientific method, scientists are able to study natural acids – and how nature formed those acids. After discovering how nature forms natural acids, scientists found a way of imitating nature and are able to form synthetic or artificial acids in the laboratory.
In continuation, s/he explains that since acid and base can be the product of the works of scientists, to understand the chemicals very well they have to learn how scientists think and work – perhaps one or two of them will like to become a scientist too! The teacher thereafter proceeds to step 2.
Step 2: Scientific Method
In follow up of step 1, the teacher explains scientific method in the most elementary way. S/he explains as below:
There are a standard steps that every scientist adopts in their works. These set of steps are collectively known as scientific method. There many steps in scientific method can be summarized into 6. These are explained with an illustration using a pseudo-narration of how a scientist made the first perfume from a vanilla plant (flower).
|STEPS IN SCIENTIFIC METHOD
||ILLUSTRATION WITH VANILLA
||Careful Observation and Questioning:
Scientists use all their senses to observe something carefully then asks a lot of questions
|The scientist walked along a flower orchard then perceives the scent of the flowering vanilla plants. He stopped and asked “what’s this sweet scent I perceive?” and “Where is it coming from?”The scientist moved forth and hence, trying to get the direction of the scent. Finally, he is convinced that the sweet scent was coming from the vanilla plants – how? Then he asked himself another question: “which part of the plant is producing the scent – leaf, petal or the nectar?” He believes if only he could get the scent into bottles, it will help a lot of people by giving them sense of importance after wearing it. In turn, he will also get money from the sale of the perfume. So to achieve the objective of getting the scent into bottles, the great scientist moved to step 2.
This means to repeatedly search different people’s work to find out what they think about what you are looking for, and then compare with what you think so that you can choose the best option. When scientists research, they write down all the other people’s work they search so that they can proof their final decision.
|The scientist went to the library and read many books on vanilla plant then asked some people. In the end, he found out that the leaf, bark, root, petal and nectar of vanilla plant are all capable of producing scent.
After finding out what other people think about what they are looking for and comparing with theirs, scientists will make thoughtful guesses
|Since the scientist is interested in removing the scent from the plant and put it into bottles, he has to find out the part in which it will be easiest to remove the scent. In this regard, he thought for a long time then assumed that it will be possible to extract the scent into bottles thus:
1. The nectar will be the easiest part from which the scent can be extracted but the volume of the scent will not be much.
2. The petals will be the next in line of ease of extracting the nectar but the quality of the scent will be low.
3. It will be difficult to extract the scent from the root
||Performing Experiment or Experimentation
This is to practically or physically test the hypotheses or thoughtful guesses so as to know whether it is correct or not
|To confirm his assumptions, the scientist took some of the flower to the laboratory. And taking each part at a time, the scientist tried to extract the scent into bottles. After each extraction, he measured and recorded the length of time, quality and quantity of the scent.
After experiment, scientists study the record or result of the experiment to see if it meets their assumptions
|After extracting the scent the scientist studied his record carefully so that he can make final decision
After a careful study of the record or result, the scientist will choose whether to his assumptions were correct or not. If correct, he tell others about it and if not, he go back and start from step 2 again
|After studying his record carefully, the scientist saw that his guesses were correct – he extracted vanilla scent from vanilla plant. So he told a lot of people about and they bought it from him.
Stage Evaluation Question on Scientific Method
Following the explanation of scientific method, the teacher guides the pupils to apply scientific method to spurn curiosity and provide answer to questions. See the example below.
- A boy noticed that ice melt quit fast in water. So he became curious and asked “Does ice melt faster in other liquid? Use scientific method to answer the boy’s question.
- First, select the “other liquid” you want to test – in this case let us choose juice. Now the next step in scientific method after observation is research. So, go and find out (from science books and adults) about melting of ice.
- What causes ice to melt? Answer: _________________________________
- Does ice melt at the same speed in other liquid like juice as it does in water? Answer: _________________________________
- What makes ice to melt faster in one liquid than in another? Answer: _________________________________
- Next step is to develop hypothesis – make a thoughtful guess or prediction.
- Based on the information you gathered from your research, do you think ice will melt faster in juice than it does in water? _________________________________
- Why do you think so? _________________________________
- Now, test your hypothesis by carrying out this experiment:
- Get a glass of juice, a glass of water, two cubes of ice and a stopwatch. If possible get a thermometer. Make sure the volume of water and juice are equal. Also use your thermometer to measure and make that the temperature of the juice and water are equal. Finally, the sizes of the ice cube should be the same – e.g. 15cm3.
- Starting with the glass of water, measure and record the temperature and volume of the water – say 35cl each.
- Then set your stopwatch to 00:00 – zero minute and zero second.
- Finally, while starting the stopwatch, place the ice cube in the water and allow it to stay until it melts.
- After about 15 minutes, inspect the ice cube and record how much it has melted.
- Note when the ice cube melt completely and record the time.
- Repeat step ii through VI with the other liquid – juice.
- Following the experiment is data analysis. Study what you have recorded and compare the results.
- In which liquid did more ice melted after 15 minutes?
- In which of the liquids did it take longer for the ice to melt completely?
- Finally, draw your conclusion.
- Was your hypothesis correct?
- What is your final conclusion?
- If your hypothesis was not correct, what do you think caused it?
- The teacher may give the pupils other simple experiments to do. For this reason, check out some kids science project websites. I recommend Little Bins for Little Hands and Kids Academy.
- S/he may also allow the pupils to come up with their observation and try it out.
Step 3: Concept of Atoms
The teacher having explained scientific method in step one above, now continues the lesson with concept of atoms and elements.
With reference to the earlier discussion under how scientists make acid and bases in step one above, the teacher informs the pupils that they will learn the findings (conclusions) of the scientists about acids and bases and how they are naturally formed.
Meaning of matter
To explain the findings of earlier scientist with respect to acids and bases, the teacher first of all explains that the quests of these scientists were not really about acids and bases. Instead, the curiosity of the scientists emanated from the origin of matter.
The teacher thereafter explains what matter is – anything that has mass and occupies space. The teacher may simplify this by telling the pupils that matter is the scientific name for “something or anything they can see, perceive or feel”. That is, anything they can see like book, tree, human being, e.t.c; perceive like perfume, smoke, e.t.c, and feel is matter. The teacher wraps this by telling the pupils that matter is sometimes referred to as substances.
Discovery of Atom and Atomic Theory
Following the explanation of matter, the teacher explains that the discovery of how nature forms acids and bases started from origin of matter.
Democritus’ theory of the universe
Following this, the teacher explains a very long time ago, at about 400BC, a man called Democritus wanted to know how matter is formed or what make up matter. He thought that if you take a piece of matter and divide it and continue to divide it you will eventually come to a point where you could not divide it any more. This indivisible part of matter is what Democritus called atom.
Democritus also wrote some theories about atom. He called this the theory of the universe. A theory to a scientist is a rule statement of a hypothesis that is proven by experiments. Two among the rule statement of Democritus’ theory of the universe are:
- All matter consists of atoms, which are bits of matter too small to be seen.
This rule statement means all matter (that is, everything) is made up of extremely small pieces of itself and these extremely small pieces of any matter is called atoms of that matter. For example, an orange is made up of extremely small pieces of the orange, combined to form the whole orange. These extremely small pieces of the orange may be called atoms of the orange – and it cannot be seen.
- Each atom (of a different substance) is different in size, weight and shape
This second rule statement of Democritus’ theory of the universe means that all atoms are not the same. The atoms of an orange are different from the atoms of a stone – in size, weight and shape.
Dalton’s atomic theory
Many people believed Democritus’ theory of the universe. And many scientists continue to experiment it even long after he died. In 1808, another man named John Dalton experimented and formed his own theory about atom which is known as Dalton’s Atomic theory.
Two among the rule statements of Dalton’s atomic theory are:
- Atoms are indivisible particles
- Atoms can neither be created nor destroyed
- All chemical changes result from the combination or separation of atoms
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