28, When a substance undergoes a physical change a) It changes its composition b

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28, When a substance undergoes a physical change a) It changes its composition but not its appearance b) It changes it appearance hut not its composition c) Changes both its appearance and composition d) None of the above 29, When a substance undergoes a chemical change a) The composition and color does not change b) A substance is converted to a new substance with similar properties c) A substance is converted to a new substance with different properties omposcs CALCULATION PROBLEMS 1. A metal object has a density of 0.785 g/ml and a volume of 75 ml. What is the objects' mass? 2. A metal object has a mass of 9.87 grams. When it was placed in a graduated cylinder containing 50.0 ml of water, the water level rose to 63 ml. What is the density of the metal A flame test for a white colored solution gives an orange color when the wire was placed at the flame. 3. When reacted with AgNO3 (silver nitrate) it gave a color change, and this color later disappeared when nitric acid HNO3 was added. What is the identity of the compound? 4. Indicate whether red blood cells will undergo hemolysis or crenation, or no change in each of the following solutions: water, 10% NaCl, and 2 % glucose 5. Predict what will happened when a solution that is mixed with Benedict solution and later heated turns 6. Predict what will happen when a solution that is mixed with the iodine reagent turns blue-black 7. Predict what will happen when a solution is mixed with silver nitrate AgNO3 and it forms a white precipitate 8. The pH of the body is between 7.35 and 7.45. In order to treat a person with pht disorders, the doctor recommends treatment with sodium hydrogen carbonate since the patients' pH in the blood is 7.29. Would this treatment increase or decrease the pH value? Explain 9. List the 4 criteria to identify when a chemical reaction occurs. 10. What is the difference between solutions, colloids, and suspensions? 1I. What evidence of a chemical reaction would you see on the following phenomenon a) Burning a stick b) Rusting of metal c) Dropping an alka-Seltzer in a glass of water d) Bleaching a stain. e) Mixing vinegar and baking soda f) Explosion of fireworks h) Milk going sour

Explanation / Answer

Ans 28 : b) It changes its appearance and not composition.

When the material undergoes physical change , its appearance changes. If it undergoes a change in composition , it is called as chemical change.

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