Acids, bases, salts

The Acids, bases, salts SAILS inquiry and assessment unit aids students to explore acids, bases and salts as substances that are used in everyday life. The seven activities outlined seek to motivate students to understand basic chemical properties and how to detect acids and bases through experimentation using an indicator. Prior knowledge of terms like chemical elements, compounds, molecular structure, dissolution, is necessary for students to interact effectively with the new material. The unit complies with the curricula of lower second level schools, ages 12-15 years, and the suggested amount of time needed to complete all the activities is about 4 hours.

The students are given the opportunity to develop a number of inquiry skills such as planning investigations, developing hypotheses, forming coherent arguments and working collaboratively. In addition, they have the opportunity to enrich their scientific literacy and reasoning capabilities through making justified arguments and presenting evidence to back up conclusions. Assessment opportunities include teacher observation, formative assessment during class, assessment of student artefacts, use of rubrics and student self assessment.

This unit was trialled in Greece, Turkey and Slovakia, producing six case studies. The teaching approach in all case studies was that of guided inquiry. Inquiry skills assessed were planning investigations, scientific reasoning and forming coherent arguments. Use of a broad range of assessment methods is detailed, including classroom dialogue, peer- and self-assessment and evaluation of student artefacts.

Unit booklet

Key content / concepts

Acids, bases and salts in everyday life
Chemical properties – how to detect acids and bases
Use of indicators

Level

Lower

Inquiry skills and competencies assessed

Planning investigations
Developing hypotheses
Forming coherent arguments
Working collaboratively
Scientific reasoning
Scientific literacy

Assessment methods

Classroom dialogue
Teacher observation
Peer-assessment
Self-assessment
Worksheets
Student devised materials
Other assessment items

The Acids, bases, salts SAILS unit was developed by the team at the University of Piraeus Research Centre (UPRC), as part of the SAILS project. The unit includes seven learning activities aimed at lower second level students, aged 12-15 years. The first phase is an introduction to the concepts of acids, bases and salts. Activity A: Introduction serves as an opportunity to review prior knowledge and develop hypotheses. The second phase is experimental investigation of proposed hypotheses, in which the students plan investigations and implement them. In this phase, students investigate qualitative and quantitative measurement of pH for commonplace acids and bases (activities B-C), before being introduced to salts in Activity D: Identifying salts. The final experimental investigation, Activity E: Acids dissolve salts, bases dissolve fats, enables students to distinguish between acids, bases and salts, based on their solubility properties. The third phase of the unit focuses on drawing conclusions – in Activity F: Conclusions, students consolidate and interpret their results, and relate them to their initial hypothesis. The final phase of this unit, Activity G: Everyday application, looks at application of the acquired knowledge in everyday life, enhancing students’ scientific literacy through understanding of real world applications of acids, bases and salts.

There are many worksheets provided in each phase to collect evidence of both content knowledge and development of inquiry skills. Provided within the unit are a set of dedicated assessment tools. For example, rubrics that may be used for assessing developing hypotheses and forming coherent arguments are included. Evaluation of the pH scale can be assessed through peer-assessment (using a rubric), while scientific literacy and content knowledge is assessed through examining the answers given to questions about acids and bases in everyday life (peer-assessment using a rubric). Assessment of working collaboratively is achieved through peer- and self-assessment.

Below you can find the full inquiry and assessment unit for download, as well as an archive with classroom materials, including student worksheets and assessment tools for teachers to be used during the activities if available.

Unit booklet Classroom materials

Activity A: Introduction

Concept focus	Reviewing background to the task Theoretical introduction
Inquiry skills focus	Developing hypotheses
Scientific reasoning	Classification of substances as acids and bases
Assessment methods	Classroom dialogue Worksheets

In this initial activity students are introduced to examples of acids and bases from everyday life, e.g. lemon juice, vinegar, baking soda, toothpaste. Properties of acids and bases are explored initially using the senses (taste, smell, appearance), and then group discussions are used to develop scientific classification of the substances. Students use this knowledge to develop hypotheses, which they can investigate through experimentation.

Activity B: Qualitative classification of substances using a pH indicator extracted from red cabbage

Concept focus	Features of acids and bases pH and indicators
Inquiry skills focus	Planning investigations Forming coherent arguments Working collaboratively
Scientific reasoning	Making predictions Classification of substances as acids or bases Drawing conclusions
Scientific literacy	Evaluate and design scientific inquiry
Assessment methods	Classroom dialogue Worksheets Student devised materials

In this activity, students use a red cabbage indicator to carry out qualitative measurement of pH of a range of everyday acids and bases. The activity can begin with preparation of the indicator, before planning an investigation to use the indicator to investigate the hypotheses proposed in Activity A: Introduction. Students can use their results to classify the samples based on colour change.

Activity C: Measurement of the numerical value of the pH

Concept focus	Features of acids and bases pH and indicators
Inquiry skills focus	Planning investigations Forming coherent arguments Working collaboratively
Scientific reasoning	Making predictions Classification of substances as acids or bases Drawing conclusions
Scientific literacy	Evaluate and design scientific inquiry
Assessment methods	Classroom dialogue Worksheets Student devised materials

In this activity, students measure the numerical value of the pH for each sample substance. For this purpose they can use a pH meter, universal indicator or other suitable methods. They can compare the numerical results to the classification by colour carried out in Activity B and construct a pH scale of their results.

Activity D: Identifying salts

Concept focus	pH and indicators Identifying salts
Inquiry skills focus	Planning investigations Forming coherent arguments Working collaboratively
Scientific reasoning	Making predictions Classification of substances as acids or bases Drawing conclusions
Scientific literacy	Evaluate and design scientific inquiry
Assessment methods	Classroom dialogue Worksheets Student devised materials

During this experiment students will be able to ascertain the existence of salts by using the red cabbage indicator. They investigate chalk and cooking salt using red cabbage indicator, and observe that these substances do not behave like acids or bases. Building on this observation, students come to understand that there is an additional category of substances – salts.

Activity E: Acids dissolve salts, bases dissolve fats

Concept focus	Features of acids and bases pH and indicators Identifying salts
Inquiry skills focus	Planning investigations Forming coherent arguments Working collaboratively
Scientific reasoning	Making predictions Classification of substances as acids or bases Drawing conclusions
Scientific literacy	Evaluate and design scientific inquiry
Assessment methods	Classroom dialogue Worksheets Student devised materials

In this experiment students will find out how salts can be identified through their basic property of dissolution in the presence of acids. Conversely, they observe experimentally the property of bases to dissolve fats.

Activity F: Conclusions

Concept focus	Reviewing results of experiments Drawing conclusions
Inquiry skills focus	Forming coherent arguments
Scientific reasoning	Drawing conclusions based on evidence
Scientific literacy	Interpret data and evidence scientifically
Assessment methods	Classroom dialogue Worksheets

During this phase, groups summarise through discussion their observations from the previous activities. They draw conclusions based on the evidence they have collected, and relate this to their original hypotheses.

Activity G: Everyday application

Concept focus	Drawing conclusions Knowledge transfer
Inquiry skills focus	Forming coherent arguments
Scientific reasoning	Forming conclusions based on evidence
Scientific literacy	Understanding how things relate to real world context
Assessment methods	Classroom dialogue Worksheets Other assessment items

In this phase gained knowledge is connected with everyday life. Each group will have to answer some questions, which involve acids and bases related to everyday life. The exercise ends with an individual test.

This unit was trialled in three countries producing six case studies of its implementation (CS1 Greece; CS2 Turkey; CS3-CS6 Slovakia). All the case studies were implemented by teachers who had some experience in teaching through inquiry. However, the students involved had not been taught through inquiry before except for the case studies CS4 Slovakia (one lesson experience from CS3 Slovakia), and CS6 Slovakia (one lesson experience from CS5 Slovakia).

The ages of the students involved in the case studies were 12-15 years: 12 years for CS1 Greece, 14-15 years old in CS2 Turkey and 13-14 years in CS3-CS6 Slovakia. The students in each class were of mixed ability and mixed gender. CS1 Greece was implemented in 4.5 hours, while CS2 Turkey, CS3 Slovakia and CS4 Slovakia were implemented in one hour each. Finally, CS5 and CS6 (both Slovakia) were implemented in a total of five lessons.

Opportunities for assessment of the key SAILS skills and competencies were identified throughout the activities, and assessment methods include classroom dialogue, peer- and self-assessment and evaluation of student artefacts (worksheets, pH charts). CS1 Greece includes a post-implementation test.

The inquiry approach used in all the case studies was that of guided inquiry, where the teacher identifies the problem and poses multiple questions that lead the students to answer inquiry questions. In this mode of inquiry, students are able to exploit pre-existing knowledge in order to formulate initial hypotheses, which will then help them structure their research (plan investigations). The students in all the case studies worked in groups throughout the lessons but there was variation in both how the groups were chosen and the group size.

The starting point for the case studies CS1 Greece and CS2 Turkey was Activity A: Introduction. CS1 Greece implemented all activities, while CS2 Turkey was focused on activities A-E (introduction and experimental). CS3 Slovakia was based on activities B-C (experimental, qualitative and quantitative measurement of pH), and the same class later participated in CS4 Slovakia, where the starting activity was Activity D: Identifying salts. Finally, CS5 and CS6 (both Slovakia) include activities that the teacher proposed as adaptations of Activity D: Identifying salts. The teacher applied these activities into the teaching of topics "Exploring acidity of solutions" and "Exploring alkalinity of solutions" within the unit "Chemical compounds" with students of 8th grade at primary school.

Within the six case studies, the inquiry skills of developing hypotheses, forming coherent arguments, planning investigations, and working collaboratively were assessed in different ways. Additionally the content knowledge and evidence of scientific literacy and scientific reasoning was assessed. While the case studies highlighted the development of several inquiry skills, assessment was only described for a few of these skills. For some skills, the assessment was carried out after class and was based on a written artefact produced in class. In other situations, formative assessment guided the student learning during the class.

Below you can find the full inquiry and assessment unit for download (excluding the case studies), as well as an archive containing all the case studies.

Unit booklet Case studies

CS1 Greece

Concept focus	Features of acids and bases pH and indicators Understanding salts
Activities implemented	Introduction Qualitative classification of substances using a pH indicator extracted from red cabbage Measurement of the numerical value of the pH Identifying salts Acids dissolve salts, bases dissolve fats Conclusions Everyday application
Inquiry skills assessed	Planning investigations Developing hypotheses Forming coherent arguments Working collaboratively
Scientific reasoning	Drawing conclusions
Scientific literacy	Everyday applications of acids and bases
Assessment methods	Classroom dialogue Teacher observation Peer-assessment Self-assessment Worksheets Student devised materials Other assessment items
Level	Lower
Age	12
Prior experience with inquiry	No experience

This case study describes full implementation of the Acids, bases, salts SAILS inquiry and assessment unit. Each of the inquiry skills and competencies identified in the SAILS project were assessed, through a combination of classroom dialogue, peer-assessment, self-assessment, evaluation of student artefacts and a post-implementation test. The teacher prepared student rubrics for peer-assessment, and a self-assessment tool for evaluation of developing hypotheses.

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CS2 Turkey

Concept focus	Features of acids and bases pH and indicators
Activities implemented	Introduction Qualitative classification of substances using a pH indicator extracted from red cabbage Measurement of the numerical value of the pH Identifying salts Acids dissolve salts, bases dissolve fats Conclusions
Inquiry skills assessed	Planning investigations
Scientific reasoning	Observation Classification Making comparisons
Scientific literacy	Understanding acids and bases that are found in everyday life
Assessment methods	Classroom dialogue Teacher observation Student devised materials
Level	Lower
Age	14-15
Prior experience with inquiry	No experience

In this implementation, the teacher did not provide worksheets and instead students prepared their own documentation for the inquiry. Assessment of student’s skills in planning investigations was achieved through teacher observation. Students’ scientific reasoning capabilities and scientific literacy were assessed through classroom dialogue. The teacher identified five key criteria for success – students’ answers to questions, measurements, categorisation of samples, understanding of use of pH paper and suitable examples from daily life.

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CS3 Slovakia

Concept focus	Features of acids and bases pH and indicators
Activities implemented	Qualitative classification of substances using a pH indicator extracted from red cabbage Measurement of the numerical value of the pH
Inquiry skills assessed	Developing hypotheses
Scientific literacy	Explaining phenomena scientifically Designing scientific inquiry
Assessment methods	Classroom dialogue Self-assessment Worksheets
Level	Lower
Age	14
Prior experience with inquiry	No experience

Two activities from the Acids, bases, salts SAILS inquiry and assessment unit were chosen as part of the thematic unit Chemical Compounds in the Slovakian state curriculum for chemistry. The assessment focus was on developing hypotheses and enriching scientific literacy, looking at students’ ability to explain phenomena scientifically and to design scientific inquiry. Assessment methods include classroom dialogue, evaluation of student devised materials and self-assessment.

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CS4 Slovakia

Concept focus	Neutral solutions Neutralisation reactions
Activities implemented	Identifying salts Acids dissolve salts, bases dissolve fats
Inquiry skills assessed	Working collaboratively
Scientific reasoning	Addressing problem through logic and use of evidence Forming conclusions
Assessment methods	Classroom dialogue Self-assessment Worksheets
Level	Lower
Age	14
Prior experience with inquiry	Some experience

In this case study, students investigated salts and neutralisation. The students were asked to explain two key observations; first, the indicator did not change its colour in solutions of powdered chalk and kitchen salt and secondly, mixing of an alkaline and acidic solution created a neutral solution. The teacher evaluated students’ responses to assess their scientific reasoning capabilities. Skill in working collaboratively was self-assessed, using the assessment tools from the original unit.

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CS5 Slovakia

Concept focus	How can chemists recognise an acid? Getting to know indicators
Activities implemented	Qualitative classification of substances using a pH indicator extracted from red cabbage Measurement of the numerical value of the pH
Inquiry skills assessed	Developing hypotheses
Scientific literacy	Explaining phenomena scientifically Designing scientific inquiry
Assessment methods	Classroom dialogue Self-assessment Worksheets
Level	Lower
Age	13-14
Prior experience with inquiry	No experience

The teacher wanted to make students aware that acids are everywhere in everyday life, and not simply dangerous substances. The task “how can chemists recognise an acid?” was designed to allow students to measure the pH of common substances and laboratory acids. Students’ skill in developing hypotheses and their scientific literacy were assessed, through evaluation of responses in worksheets and self-assessment.

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CS6 Slovakia

Concept focus	How can chemists distinguish acid from base?
Activities implemented	Identifying salts
Inquiry skills assessed	Developing hypotheses
Scientific reasoning	Drawing conclusions
Scientific literacy	Explaining phenomena scientifically
Assessment methods	Classroom dialogue Self-assessment Worksheets
Level	Lower
Age	13-14
Prior experience with inquiry	Some experience

This case study describes a lesson focusing on bases, in which a modified version of Activity D: Identifying salts was implemented. The students investigated the inquiry question, “How can chemists distinguish an acid from a base?” The teacher provided a worksheet, to guide the students through the inquiry process and to use for evaluation after the lesson. Key skills assessed were developing hypotheses, scientific reasoning and scientific literacy.

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Acids, bases, salts

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