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- (b) Certain chemical reactions are characterised by a change in the colour of the reactants. When a few pieces of iron are dropped into a blue coloured copper sulphate solution, the blue colour of the solution fades and turns into light green.
www.knowledgeboat.com/learn/class-8-icse-concise-chemistry-selina/solutions/BAe97V/chemical-reactionsChapter 6: Chemical Reactions | Selina Solutions Concise ...
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A change of state of matter, change in colour, odour, solubility, etc. all are examples of physical change. During a physical change, neither the composition nor the chemical nature of matter is changed. During this change, molecules rearrange themselves without affecting the internal composition.
- Law of Conservation of Mass Questions - BYJU'S
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- Selina Solutions Class 8 Concise Chemistry Chapter 2 Physical ...
Define: (a) Physical change (b) Chemical change. Solution:...
- Law of Conservation of Mass Questions - BYJU'S
- Define: (a) Physical change. (b) Chemical change. Solution: (a) Physical Change: A physical change is a temporary change in which no new substance is formed, and the chemical composition remains the same, even though its physical properties like colour, state, shape, size etc.
- Classify the following as a physical or a chemical change. (a) Drying of wet clothes. Solution: Physical change. (b) Manufacture of salt from seawater.
- Fill in the blanks. Solution: (a) The process of a liquid changing into a solid is called freezing. (b) A change, which alters the composition of substances, is known as a chemical change.
- Given reason: (a) Freezing of water to ice and evaporation of water are physical changes. (b) Burning of a candle is both a physical and chemical change.
- Heat Or Light
- Colour Change
- Release of Gas
- Precipitate Formation
Many reactions involve a transfer of energy. In some cases the energy may be felt as heat energy or seen as light energy. Often, both light and heat can be observed at the same time! When a reaction gives off heat, we call this an exothermic reaction. This means that heat is transferred from the reactants to the external environment. When the oppos...
A change in colour is another sign that a chemical reaction has occurred. A good example of this is when something rusts. Pure iron is naturally silver in colour. We don’t usually observe it this way on Earth because it reacts easily with the oxygen in the air. The balanced chemical equationof this reaction is:
Sometimes a chemical reaction produces a gas as one of its products. When this happens, we can observe bubbles or fumes. An example of a chemical reaction that produces a gas is the reaction between baking soda and lemon juice (citric acid). If you mix baking soda with lemon juice (or vinegar), both substances quickly react to form bubbles. The bub...
Sometimes when two solutions undergo a chemical reaction, one of the new products formed from the reaction is not soluble. This means that it is not able to dissolve in the new solution. Instead, we can observe a solid that is distinct and separate from the solution. We call this solid a precipitate. You have probably heard the word “precipitation”...
Aug 12, 2022 · Chemical changes are frequently harder to reverse than physical changes. Observations that indicate a chemical change has occurred include color change, temperature change, light given off, formation of bubbles, formation of a precipitate, etc.
Get solutions of ICSE Class 8 Concise Chemistry Selina Chapter 2: Physical and Chemical Changes. Clear your Chemistry doubts instantly & get more marks in Chemistry exam easily. Master the concepts with our detailed explanations & solutions.
Aug 24, 2023 · Key Concepts. Whether a solution is acidic or basic can be measured on the pH scale. When universal indicator is added to a solution, the color change can indicate the approximate pH of the solution. Acids cause universal indicator solution to change from green toward red. Bases cause universal indicator to change from green toward purple.
16.State the colour of a strong acid with universal indicator Red 17.State the colour of a weak acid with universal indicator Orange/ yellow 18. State the colour of a neutral solution with universal indicator Green 19. State the colour of a weak alkali with universal indicator Blue 20. State the colour of a strong alkali with universal indicator
