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The correct answers are options C, that is, silver tarnishes and becomes black when exposed to oxygen, and option E, that is, diesel fuel burns when it is heated.
Chemical changes refer to the modifications in which the chemistry at molecular level is modified as the initial substance gets transformed into a new and different final substance. This change occurs with the dissociation of old bond and production of new bonds respectively.
Silver gets tarnished and becomes black when exposed to oxygen. This refers to a chemical change as silver a white and lustrous substance gets transformed into a tarnish black final substance. However, silver does not easily react with oxygen at usual circumstances. It easily reacts with sulfur comprising components in the air and generates black compound as Ag₂S.
Burning of diesel fuel when it is heated. Diesel refers to a mixture of hydrocarbons varying approximately from C₁₀H₂₀ to C₁₅H₂₈. When these hydrocarbons get burnt they generate novel substances, that is, carbon dioxide and water. Hence, it is also a chemical reaction.
Answer: The correct answer is Heterogeneous mixture
Explanation:
Heterogeneous mixture are those mixture in which:
- Substance is distributed in non uniform manner.
- Two distinct layers are formed
Thus when water and dirt are mixed together it results in the formation of a heterogeneous mixture and after sometimes two different layers will be observed.
Hence, in the bottle there is a heterogeneous mixture of water and dirt.
Answer:
Photosynthesis removes carbon from the atmosphere, and cellular respiration releases carbon back into the atmosphere.
Explanation:
The first option clearly expresses the relationship between photosynthesis and cellular respiration.
Cellular respiration releases carbon back into the atmosphere whereas photosynthesis removes the carbon from the atmosphere.
Photosynthesis is the process whereby green plants manufacture their food using carbon dioxide and water.
In cellular respiration, the product of the photosynthesis is used by organisms to produce energy.
Answer:
See explanation
Explanation:
Iodine solution is used to test for starch. A positive test for starch gives a blue-black color.
The fact that the color of the apple remained the same is indicative of the fact that starch was not contained in the apple.
A change in the color of potato indicates the presence of starch in the potato.
The fact that iodine did not react with apple should not be taken to mean that apples contain no starch at all. Starch changes gradually to sugar as fruits ripen. This is why the apple gave a negative test for starch.
