Acids, Bases and Salts. 2. CHAPTER. You have learnt in your previous classes that the sour and bitter tastes of food are due to acids and bases, respectively. Acids, Bases and Salts. 5. We use in our daily life a large number of substances such as lemon, tamarind, common salt, sugar and vinegar. Do they have. Chapter Acids, Bases, and Salts. Key topics: pH scale; acid-base properties of water. Ka = acid ionization constant; Kb = base ionization constant. Polyprotic.
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1 Acids and Bases. 2 Strength of Acids and Bases. Lab Acid Concentrations. 3 Salts. Lab Be a Soda Scientist. Virtual Lab How is the acidic concentration of a. X – Science. AK. Class CHAPTER – 2. ACIDS, BASES AND SALTS (Notes). ❑. Acids. Bases. – Sour in taste. – Bitter in taste. – Change the blue litmus to red. ACIDS, BASES AND SALTS. Before we discuss the ways in which chemists manage to classify all of the various substances in the universe, we should spend .
Universal Indicator: This is a substance that changes color when added to another substance depending on its pH.
The indicator and the substance should be in aqueous form. Litmus Paper or Solution: This indicator is present in two colors: red and blue.
We use blue litmus if we want test a substance for acidity. We use red litmus if we want to test a substance for alkalinity. If it is used as solution it turns purple.
Note: use damp litmus paper if testing gases. Phenolphthalein: This is an indicator that is used to test for alkalinity because it is colorless if used with an acidic or neutral substance and it is pink if it is used with a basic substance. Methyl Orange: This indicator gives fire colors: Red with acids, yellow with neutrals and orange with bases.
Acids: Acids are substances made of a hydrogen ion and non-metal ions. All acids must be in aqueous form to be called an acid. For example Hydrochloric acid is hydrogen chloride gas dissolved in water.
This is called ionization or dissociation. The more ionized the acid is the stronger it is, the lower its pH. It is fully ionized.
It is a weak acid. It is partially ionized. Note: Acids with pH 3 or 4 can be considered moderate in strength.
Solutions of strong acids are better conductors of electricity than solutions of weak acids. Try repeating their answers using the correct language. With practice, students can manage their own practical talk within their group. Structured talk activities should have a strict time limit. Scaffolding, such as sentence stems, encourage both listening and responding to each other. Use the video as a prompt to draw out ideas of corrosion. Degradation is a change in the bulk properties of a material, which will look different, become weaker or even break apart because of chemical changes.
This description encourages students to see materials at both the macroscopic bulk level and the submicroscopic particle level. For example, the sodium hydroxide solution is added to the aluminium can, which breaks apart with the release of gas macroscopic , because the sodium hydroxide particles are reacting with the aluminium particles to form an aluminium salt and hydrogen gas sub-microscopic.
This will make it harder for students to develop a solid understanding of how and why chemical reaction proceed. Concept mapping is a useful tool for reinforcing how this topic links across the curriculum. Provide students with opportunities to practice both longer answer four and six mark and multiple-choice questions one mark in preparation for exams. Display the question and give the students two minutes to write their answer on mini-whiteboards.
Importantly, ask them to write why they chose their answer. This provides the opportunity to identify miscomprehension and provide immediate feedback. In 14—16 teaching, a more sophisticated model of acidity is used, based on hydrogen and hydroxide ions. Neutralisation is defined as the reaction of hydrogen ions and hydroxide ions to produce water.
Finally, there are specific apparatus and techniques that must be used and understood including rates of reaction and titration see our guides to practical work in GCSE specifications.
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Naomi Hennah suggests ideas, resources and activities for your classroom. What students need to know Acids are hydrogen-containing substances with a sour taste that form solutions with pH values less than 7. Bases are a group of substances that neutralise acids. Soluble bases are called alkalis. They have a slippery, soapy feel and form solutions with pH values greater than 7. Common examples include sodium hydroxide, magnesium hydroxide, sodium hydrogen carbonate sodium bicarbonate , sodium hypochlorite and ammonia.
Neutralisation is a reaction between an acid and an alkali that forms a salt and water. Salts are odourless and have a salty taste, and many are soluble in water. Common examples include sodium chloride, potassium iodide, calcium carbonate and copper sulfate.
Citric acid is what makes the sour taste of lemons, oranges and other citrus fruits, while acetic acid gives vinegar its sour taste.
An acid will turn litmus paper red.
Litmus is a vegetable dye that turns red to indicate an acid and blue to indicate a base. Acids also contain combined hydrogen. According to the website Journey Into Science, when metals such as zinc are placed in an acid, a reaction will occur. The acid and zinc will bubble and release hydrogen gas. Acids will release hydrogen in water as well.
Acids also conduct electricity and react with bases to form water and salt. Acids are classified as being either strong or weak. A strong acid detaches or separates in a water solution and a weak acid does not. Bases taste bitter and are slippery when dissolved in water.