The correct answer is (A)
Burning of wood is a chemical change as new substance is formed during the burning of wood which is not reversible.
Now, what happened during the burning of wood?
In the case of burning wood, stored potential energy( in the form of chemical energy) in the log is released due to heating by other excited atoms. This chemical reaction is called combustion that requires oxygen. We can also say that combustion is change of potential chemical energy into kinetic energy in the form of heat.
Babies typically do not show social smiles
until four to six weeks of age.
Any smiling before that time, it may not be deliberate. It's usually only a sign that the baby is
comfortable, either they just urinated or they just ate.
At
first, the baby smiles at every one but after
several months, most babies save their smiles for people they know.
Answer:
Limestome
Explanation:
I took the test u welcome
Hola amigo mi no hablas ingles mi only hablas español
Answer: The NEGATIVE CONTROl is the test tube that is filled with ONLY distilled water.
Explanation:
A negative control of an experiment is carried out alongside the main primary experiment except that the treatment is changed to something that is predicted to have no result. In the negative control, the student does not expect any response. This would help the student compare the result of a new experiment against an already known existing results.
Analysing the experiment carried out by the student, She filled two test tubes with distilled water and placed a piece of Elodea in one of the tubes, leaving the other without a plant. The other test tube that contains only distilled water is the negative control because she wasn't expecting any result from it. It's also served as a control sample to the primary experiment. This is observed as she blew in each tube to add carbon dioxide, which caused the distilled water to become more acidic. This would help the student know that the that experimental results are valid and to ensure that time is saved.