Scientific Method | Physics for EmSAT Achieve PDF Download

Introduction

The objective of science is to provide accurate explanations for observed natural events or phenomena. Scientists employ the scientific method as a systematic approach to their work, which involves the following steps:

• Proposing a hypothesis: This is an initial theory or explanation put forward to account for an observation.
• Making predictions: Based on the hypothesis, scientists make predictions that suggest how changing certain factors will influence the outcome.
• Planning an experiment: An experiment is designed to test the predictions and the underlying hypothesis. It is crucial to carefully select appropriate apparatus, materials, and techniques for the experiment.

Apparatus:

• Various containers such as test tubes, boiling tubes, beakers, and flasks are commonly used.
• Measuring apparatus like timers, rulers, thermometers, burettes, pipettes, and measuring cylinders are employed.
• Heating and electrical apparatus, including Bunsen burners, electric heating mantles, water baths, power packs, and associated accessories like leads, crocodile clips, and electrodes, may be required.

Chemicals:

Different types of chemicals are utilized, including salts, acids, alkalis, metals, organic compounds (such as alkanes, alkenes, and alcohols), and solvents for analysis, such as indicators and substances for chemical tests.

Techniques

• Standard measurement techniques are employed using specific apparatus. Examples include using thermometers to measure temperature, pH meters for pH, timers for time, digital balances for mass, measuring cylinders for liquid volume, burettes for liquid volume in titration, and gas syringes for gas volume.
• Methods of analysis are employed, including chromatography, flame tests for identifying metal ions, chemical tests for identifying gases or ions, and titration.
• Methods for carrying out reactions involve test tube reactions, various heating methods like Bunsen burners, electric heating mantles, and water baths, as well as electrolysis.
• By following the scientific method and employing these techniques, scientists are able to gather data and draw meaningful conclusions about the natural world.

Ensuring Valid Measurements

When planning to collect measurements, it is crucial to ensure their validity.

Controlling Factors:

• To establish the validity of the experiment's conclusions, it is necessary to ensure that the observed and measured effects are indeed caused by the claimed factor.
• It is important to consider and account for other influencing factors. These factors that require control should be identified, and the experimental plan should outline the strategies for controlling them.

Solved Questions

Q.1. Two students are investigating the impact of acid concentration on the rate of reaction between marble chips and acid. They conduct tests for the first two concentrations on one day and the remaining concentrations on a hotter day the following week. Why is any conclusion drawn from this experiment considered invalid?

The conclusion cannot be deemed valid due to the difference in surrounding temperatures on the two testing days. An increase in the reaction rate could be attributed to the reaction mixture being significantly hotter, rather than solely caused by a change in concentration.

Q.2. What factors should the students have controlled?

The students should have also controlled for factors such as surface area and temperature, as these variables can affect the rate of reaction.

Q.3. How could the students ensure repeatability of their results?

To ensure repeatability, the students should consistently use the same volume of acid and the same mass of marble chips for each test.

Deciding on the Measurement Range

The range of measurements taken must be wide enough to draw valid conclusions. If the measurements are too closely spaced, it becomes challenging to have confidence in any observed trend.

How can the students enhance the experiment to obtain a wider range of results?

To collect a broader range of results, the students could extend the measurement time period, allowing for larger volumes of gas to be collected. They could also consider using higher concentrations of acid, if it is safe to do so, and increase the mass of marble chips used.

Planning for precise and accurate measurements:

• Precision: Measurements are considered precise when the results are very close in value. The choice of measuring apparatus can impact the precision of the collected data. For instance, when performing titration, using a pipette to measure the volume of sodium hydroxide in the flask would result in more precise readings compared to using a measuring cylinder, which may lead to variations between repeats and less precision.
• Accuracy: The accuracy of a numerical result refers to how close it is to the true value. For example, when monitoring the rate of reaction by measuring loss of mass, readings from a balance with two decimal places would be more accurate compared to readings from a balance with no decimal places. Accuracy ensures that the results are close to the true value.

Identifying hazards and minimizing risks:

• Chemistry experiments involve substances that can be hazardous, potentially causing harm to the eyes, skin, or respiratory system. To minimize the risk, it is advisable to use the lowest concentration of solutions, wear eye protection and gloves, and perform experiments in a fume hood.
• Procedures can also present hazards. Precautions should be taken to avoid touching hot equipment, and loose clothing or hair should be kept away from flames to reduce the risk of accidents.