This page outlines the procedure for making salts required practical in AQA GCSE Chemistry.

Steps to make a soluble salt:

1. Add 50cm³ dilute acid to a beaker and warm gently with a Bunsen burner
2. Add insoluble oxide to the hot dilute acid and stir until the base is in excess
3. Filter the mixture into an evaporating basin to remove excess base
4. Gently heat the solution in a water bath or with an electric heater to evaporate water and saturate the solution
5. Check for saturation by dipping a cold glass rod into the solution to see if crystals form
6. Leave the filtrate in a warm place to dry and crystallize
7. Decant excess solution and allow crystals to dry

Highlight: This method is one of the 4 methods of preparing soluble salts commonly taught in GCSE Chemistry.

Required Practical 2: Titration

This section describes the titration process, which is crucial for determining the concentration of an acid or alkali.

Steps for titration:

1. Measure a known volume of alkali into a conical flask using a volumetric pipette
2. Add a few drops of acid/base indicator to the solution and swirl
3. Rinse a burette with distilled water and add some acid
4. Record the initial burette reading and release a small amount of acid into the flask
5. Swirl the flask and continue adding acid until the reaction is complete
6. Record the process at least 3 times, discarding anomalous results

Vocabulary: Concordant results in titration are those within 0.1cm³ of each other, indicating precision.

Highlight: Titration is a key topic in both GCSE and A Level Chemistry, appearing in both Chemistry Paper 1 required practicals and Chemistry Paper 2 required practicals.

This page details the electrolysis required practical, an important experiment in the AQA GCSE Chemistry specification.

Procedure for electrolysis:

1. Add about 50cm³ of copper chloride solution to a beaker
2. Place the lid and insert electrodes through the holes, ensuring they don't touch
3. Attach crocodile leads to the electrodes and connect to a low voltage DC power supply
4. Set the power supply to 4V and switch on
5. Use forceps to hold litmus paper near the positive electrode
6. After a few minutes, turn off the power supply and observe the negative electrode
7. Record observations at both electrodes

Safety: Goggles must be worn, and the room should be well-ventilated due to the potential production of chlorine gas.

Highlight: Electrolysis is a process where salt solutions can be __________ to produce soluble salts and other products.

Required Practical 4: Investigating Temperature Changes

This practical focuses on observing and measuring temperature changes during chemical reactions.

Steps:

1. Place 25cm³ of hydrochloric acid solution into a calorimeter using a measuring cylinder
2. Measure and record the initial temperature of the solution
3. Add 5cm³ of dilute HCl and stir
4. Measure and record the new temperature of the solution
5. Repeat steps 1-4, increasing the amount of acid by 5cm³ each time

Safety: Eye protection should be worn during this experiment.

Highlight: This practical helps students understand exothermic and endothermic reactions, which are key concepts in AQA GCSE Chemistry Required practicals Revision.

This page covers methods for investigating how changes in concentration affect reaction rates, a crucial topic in AQA GCSE Chemistry Required practicals Paper 1.

Methods to monitor reaction rates:

1. Measuring mass change:

   • Place the reaction flask on a balance
   • Record the decrease in mass at regular time intervals
   • Plot a graph of time vs mass

2. Measuring gas volume:

   • Connect a syringe to the reaction flask
   • Measure the volume of gas formed at regular intervals
   • Plot a graph of volume vs time

3. Monitoring color change or turbidity:

   • Use sodium thiosulfate solution and hydrochloric acid
   • Place the flask over a paper with a black cross
   • Record the time taken for the cross to become invisible

Example: To investigate the effect of concentration on reaction rate using sodium thiosulfate:

1. Add 10 ml of sodium thiosulfate solution and 40 ml of water to a conical flask
2. Add 10 ml of hydrochloric acid and start timing
3. Record the time taken for the cross to disappear
4. Repeat, changing the concentration of sodium thiosulfate

Highlight: Control variables in this experiment include the volume and concentration of hydrochloric acid.

Vocabulary: Turbidity refers to the cloudiness of a solution, which increases as the reaction progresses in the sodium thiosulfate experiment.

This practical demonstrates key concepts in reaction kinetics, essential for understanding Chemistry Paper 2 required practicals and answering Making salts Required practical exam questions.

Example: Measuring gas volume or mass changes over time to track reaction progress.

Highlight: Different methods can be used to monitor reaction progress, including mass loss and gas collection.

Definition: Rf value is the ratio of the distance traveled by a substance to the distance traveled by the solvent.

Vocabulary: Capillary tube - a thin glass tube used for applying small samples in chromatography.

Highlight: Each gas has a specific test and characteristic reaction.

Example: Carbon dioxide turns limewater milky, while hydrogen produces a 'pop' sound with a burning splint.

Vocabulary: Precipitate - an insoluble solid formed during a chemical reaction in solution.

Example: Lithium produces a crimson flame, while sodium produces a yellow flame.

This page discusses methods to enhance the quality of scientific experiments in chemistry. It covers key concepts such as accuracy, precision, validity, and reliability.

Definition: Accuracy is the degree to which a result conforms to its correct value, while precision refers to the consistency of repeated measurements.

To increase accuracy:

• Use more precise equipment
• Reduce systematic errors

To increase precision:

• Use equipment with higher resolution (e.g., a stopwatch measuring to 0.01s)

Highlight: Validity in experiments refers to how appropriate the experiment is for obtaining the desired aim.

To improve reliability:

• Repeat experiments
• Add more control variables
• Have multiple people conduct the experiment
• Remove anomalous results

Vocabulary: Systematic errors are consistent inaccuracies in measurement, while random errors are unpredictable inaccuracies.

To address systematic errors:

• Use better quality equipment
• Remove anomalies
• Repeat using different techniques

For random errors:

• Take multiple readings and calculate the mean

Example: Zero error occurs when a measurement is read from a starting value other than zero. This can be addressed by using different equipment or recalibrating.