Topic: Percent concentration of the solution - density

Target group

Elementary school student (grades 7. and 8.)

Core curriculum:

Elementary school. Chemistry.

V. Water and aqueous solutions. Student:

7) performs calculations using the following notions: solubility, percent concentration (mass percentage), mass of substance, solvent mass, mass of solution, solution density (using solubility table or solubility plot).

General aim of education

The student solves the tasks with regard to density

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to calculate the mass of the indicated solution volume based on its density;

• to calculate the dissolved substance content in a given unit of volume of the solution.

Methods/techniques

• activating

  • discussion.

• expository

  • talk.

• exposing

  • film.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• projector;

• interactive whiteboard, tablets/computers;

• methodician or green, yellow and red cards.

Lesson plan overview

Introduction

1. The teacher hands out Methodology Guide or green, yellow and red sheets of paper to the students to be used during the work based on a traffic light technique. He presents the aims of the lesson in the student's language on a multimedia presentation and discusses the criteria of success (aims of the lesson and success criteria can be send to students via e‑mail or posted on Facebook, so that students will be able to manage their portfolio).

2. The teacher together with the students determines the topic – based on the previously presented lesson aims – and then writes it on the interactive whiteboard/blackboard. Students write the topic in the notebook.

3. Health and safety – before starting the experiments, students familiarise themselves with the safety data sheets of the substances that will be used during the lesson. The teacher points out the need to be careful when working with them.

Realization

1. The teacher, in order to remind students about the percentage concentration of the solution, asks to define the concept of density, giving its formula including units for its calculation. Displays abstract tasks on the multimedia board and analyzes their solutions with students.

2. The teacher presents on the multimedia board a presentation presenting a stepwise solution of the task for calculating the percentage concentration with regard to density (example task in the methodical commentary).

3. The lecturer gives the students successive tasks, asking those willing to solve them at the board (example task in the methodical commentary). The others solve tasks in notebooks - work in pairs.

4. Students perform interactive exercises from the abstract (individual work).

Summary

1. The teacher asks the students to finish the following sentences:

   • Today I learned ...

   • I understood that …

   • It surprised me …

   • I found out ...

   The teacher can use the interactive whiteboard in the abstract or instruct students to work with it

Homework

1. Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

2. Make at home a note from the lesson using the sketchnoting method.

Methodical commentary

Examples of tasks to be solved during the lesson:

Excercise 1.

What is the percentage concentration of solution obtained after dissolving 10 g of substance in 90 cm3 of gasoline? The gasoline density is 0.7 g/cmIndeks górny 3³.

Re. After dissolving 10 g of substance in 90 cm3 of gasoline, a solution of 13,(7)% was obtained.

Exercise 2.

How many grams of sulfuric acid(VI) are in a 0.7 dmIndeks górny 3³ solution with a concentration of 48.3%? The density of this solution is 1.3 g/cmIndeks górny 3³.

Re. In 0.7 dm 3 of the 48.3% solution, there are 439.53 g of sulfuric acid(VI).

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Percent concentration of the solution - density

The density of the solution is a physical quantity and means the mass of a given volume unit of the solution. This value changes with temperature. If the solution has a density of $1.05\frac{\mathrm{g}}{{\mathrm{cm}}^3},$, it means that 1 cm Indeks górny 3³ of the solution has a mass of 1.05 g.

The density of the solution can be calculated using the formula: ${\text{d}}_{\text{r}}\text{=}\frac{{\text{m}}_{\text{r}}}{{\text{V}}_{\text{r}}}$

${\text{m}}_{\text{r}}$ – mass of the solution
${\text{V}}_{\text{r}}$– volume of the solution

The density of the solution can be expressed in different units, for example: $\frac{\text{g}}{{\text{cm}}^{\text{3}}}$, $\frac{\text{g}}{{\text{dm}}^{\text{3}}}$, $\frac{\text{kg}}{{\text{dm}}^{\text{3}}}$. In our calculations we will use the following unit $\frac{\text{g}}{{\text{cm}}^{\text{3}}}$.

• The density of the solution can be calculated using the formula: ${\text{d}}_{\text{r}}\text{=}\frac{{\text{m}}_{\text{r}}}{{\text{V}}_{\text{r}}}$

• If the density of the solution is known, it is possible to determine the mass of given volume.

• The density of the solution can be expressed in different units, for example: $\frac{\text{g}}{{\text{cm}}^{\text{3}}}$, $\frac{\text{g}}{{\text{dm}}^{\text{3}}}$, $\frac{\text{kg}}{{\text{dm}}^{\text{3}}}$.