DESIGNING CALORIMETER MADE FROM VARIOUS WASTES

A research has been conducted which aims to design a waste-based calorimeter as an alternative to measuring heat for chemistry practicum in schools. Research products developed through the steps of design-based research comprising the steps of analysis, design, and development. The resulting product is a waste-based calorimeter equipped with an automatic stirrer. The container to store the reagent solution on the calorimeter is made of Styrofoam, paper, plastic, melamine, PVC and bamboo. Optimization tool was conducted to determine the heat capacity of the calorimeter and the enthalpy of neutralization. The highest accuracy calorimeter value between 78-97%. Bamboo calorimeter has the highest accuracy value (97%). Styrofoam calorimeter has the lowest accuracy values (78%). Based on the results of the validation and feasibility test it can be concluded that the product is declared valid and feasible.


INTRODUCTION
Chemistry is one branch of science that is very closely related to life so it needs to be learned by students. The concepts in chemistry are very broad, from simple concepts to very complex and abstract concepts [1].
The concept of chemistry is also obtained from experimental activities whose development is obtained through research activities.
Therefore, practicum or experimental activities are needed in studying chemistry [2].
Practical activities make it easier for students to understand the concepts being learned [3].
Through practicum, students make direct observations of chemical phenomena [4].
One of the concepts of chemistry that needs to be studied accompanied by practicum is thermochemistry. The concept of thermochemistry is a concept learned in Class XI in high school. Based on the national curriculum, the basic competencies of thermochemistry include aspects of knowledge that is understanding of various types of reaction enthalpy, Hess's law and the concept of bond energy [5] . The skill aspect developed is the determination of the change in reaction enthalpy by applying Hess's Law based on the enthalpy of formation or bond energy.
Determination of the reaction enthalpy based on the results of heat measurement using calorimetry [6].
Generally, the determination of the heat of reaction in the school laboratory using a simple colorimetric insulator is made of Theoretically, the calorimeter should absorb heat and the value of the resulting heat capacity is positive [8], [9]. Allegedly, this is due to the stirring rotation manually is not constant. In addition, the hand directly touches the ring-shaped stirrer resulting in heat transfer.
Several studies have used a calorimeter made of styrofoam [7], [10], [11], paper [12], and plastics [13]. These studies use automatic magnetic stirrers which produce high measurement accuracy. At school, the use of magnetic stirrers is an obstacle. Not all school laboratories have a magnetic stirrer.
The price of magnetic stirrer is quite expensive and can only be used in places that have electricity sources. Thus, the use of magnetic stirrers is less economical and practical. However, replacing the insulator material on the calorimeter using Styrofoam, paper, and plastic can be followed. These materials are easily obtained in everyday life and often become waste that pollutes the environment.
Based on this, the researcher considers it important to innovate a simple calorimeter used in school laboratories. The calorimeter isolator material is replaced with a variety of used materials available in the environment (other than those previously studied) and is equipped with self-made automatic stirrers.
The innovation is expected to be developed in schools by teachers and students, thus providing an alternative tool or medium to carry out lab work more interesting and fun [14], [15].

METHODS
The research product was developed using design-based research (DBR) [16].
This method consists of five stages, namely analysis, design, development, implementtation, and evaluation. However, in this study only three steps were carried out, namely the analysis, design and development stages. [17].
The analysis phase is a theoretical and empirical study to get the results of the needs analysis. At the design stage, product design, tool and material determination and product packaging. At the development stage carried out: product optimization in the laboratory, validation and feasibility test. The product validation test was conducted by three chemists, while the eligibility test was conducted by 12 prospective teacher students. Data collected from the results of the validation test products were processed and analyzed by comparing the value of r count with critical r value set that is equal to 0.3 [18]. The feasibility value (r count) is determined using equation (1).

= .
(1) The feasibility test data were analyzed by changing the frequency of answers from the questionnaire respondents into percentages.
The questionnaire obtained from the respondent is given a score and then presented with equation (2): Data obtained from the feasibility test are then interpreted using Table 1.

RESULTS AND DISCUSSION
The prototype design of the Calorimeter was made to facilitate the process of making products that meet the validity and eligibility criteria. The design is outlined in the form of images that display concrete ideas that are attractive, efficient, and effective according to the usability criteria of the product [20], [21]. The intended product Such materials cannot transfer heat from the system to the environment or vice versa [22].
Insulator material must be easily obtained in everyday life or utilize waste that can still be recycled. It is intended that products that are created are environmentally friendly and have low prices [23], [24] .   . container size specifications can be seen in Table 2.  Figure 3.      in thickness of the material used also affects the data produced [22], [32] .  Table 6.  Table 7.  [11]. This is in accordance with that stated that the teaching aids that are made must be in accordance with the subject matter so as to make it easier for students to understand the subject matter [33].
In removable. This is in line with the fact that using technology makes things easier [34] .
In the aspect of display and durability of the tool, the results of the validation have a calculated value of 0.75 and are supported by the feasibility results with a percentage of 87.50% so that it shows that calorimeters from various simple materials have a good appearance and durability so as to attract students' interest in the products used and the product can be used for a long time.
The making of calorimeter from various simple materials is adjusted to the calorimeter design that has been made as shown in Figure 2 so as to create a product that has a good appearance. Appearance becomes the main thing as a support for a work that can be enjoyed [35]. In addition to the props that have a good display can increase the attractiveness of students so that students do not get bored when using props [21].