One Marks Questions (1) Define a chemical change. (2) Give four examples of a chemical change. (3) Give four characteristics of a physical change. (4) Give an example of a chemical change that is reversible. (5) Define a physical change. (6) Classify as physical or chemical change: (i)Tearing of paper (ii)Production of biogas (iii)Butter going rancid (iv)magnetization of iron (v)Clotting of blood (7) Give four examples of a physical change. (8) Give four characteristics of a chemical change. (9) What do you understand by an exothermic chemical change Two Marks Questions Explain whether the following are physical or chemical changes. Give one reason for your answer. (1) Formation of curd (2) Ripening of fruit (3) Bending a glass tube by heating (4) Melting of wax (5) Formation of wine (6) Action of heat on blue vitriol is a physical as well as chemical change. Justify. (7) Is boiling of water, a chemical change? Give reason for your answer. (8) A person eats chocolate and then digests it. In doing so a physical and a chemical change takes place. Identify the changes and give reasons for your answer. (9) When we mix iron filings with sulfur and grind it, a physical change takes place. However, if we heat the mixture, a chemical change takes place. Explain why the former is said to be a physical change while the latter process is said to be a chemical change True and False statement (1)Chemical changes are generally accompanied by an exchange of energy. (2)A physical change is usually reversible. (3) When a magnesium ribbon burns brilliantly in air a physical change takes place. (4)Ammonium chloride dissolves in water with the absorption of heat. This is an exothermic. (1) Identify physical or chemical changes in the following: (a) A rock rolls down a slope (b) Baking of cake (c) Plucking of fruit (d) Burning of L.P.G (e) Cutting of carrots (2) Explain whether the addition of dilute sulphuric acid to iron is a physical or chemical change. (3) Heating of iodine crystals is considered to be a physical change. Explain. (4) Burning of a candle may be considered as showing physical and chemical changes occurring simultaneously. Explain
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Answer:
One Marks Questions (1) Define a chemical change. (2) Give four examples of a chemical change. (3) Give four characteristics of a physical change. (4) Give an example of a chemical change that is reversible. (5) Define a physical change. (6) Classify as physical or chemical change: (i)Tearing of paper (ii)Production of biogas (iii)Butter going rancid (iv)magnetization of iron (v)Clotting of blood (7) Give four examples of a physical change. (8) Give four characteristics of a chemical change. (9) What do you understand by an exothermic chemical change Two Marks Questions Explain whether the following are physical or chemical changes. Give one reason for your answer. (1) Formation of curd (2) Ripening of fruit (3) Bending a glass tube by heating (4) Melting of wax (5) Formation of wine (6) Action of heat on blue vitriol is a physical as well as chemical change. Justify. (7) Is boiling of water, a chemical change? Give reason for your answer. (8) A person eats chocolate and then digests it. In doing so a physical and a chemical change takes place. Identify the changes and give reasons for your answer. (9) When we mix iron filings with sulfur and grind it, a physical change takes place. However, if we heat the mixture, a chemical change takes place. Explain why the former is said to be a physical change while the latter process is said to be a chemical change True and False statement (1)Chemical changes are generally accompanied by an exchange of energy. (2)A physical change is usually reversible. (3) When a magnesium ribbon burns brilliantly in air a physical change takes place. (4)Ammonium chloride dissolves in water with the absorption of heat. This is an exothermic. (1) Identify physical or chemical changes in the following: (a) A rock rolls down a slope (b) Baking of cake (c) Plucking of fruit (d) Burning of L.P.G (e) Cutting of carrots (2) Explain whether the addition of dilute sulphuric acid to iron is a physical or chemical change. (3) Heating of iodine crystals is considered to be a physical change. Explain. (4) Burning of a candle may be considered as showing physical and chemical changes occurring simultaneously. Explain
1)Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. These processes are called chemical reactions and, in general, are not reversible except by further chemical reactions.
2)
- Burning of paper and log of wood.
- Digestion of food
- Boiling an egg.
- Milk going sour
- Chemical battery usage.
3) A physical change involves a change in physical properties. Examples of physical properties include melting, transition to a gas, change of strength, change of durability, changes to crystal form, textural change, shape, size, color, volume and density.
4)One example of a reversible reaction is the reaction of hydrogen gas and iodine vapor to from hydrogen iodide. ... In the forward reaction, hydrogen and iodine combine to form hydrogen iodide. In the reverse reaction, hydrogen iodide decomposes back into hydrogen and iodine.
5)Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes are used to separate mixtures into their component compounds, but can not usually be used to separate compounds into chemical elements or simpler compounds.