About 5 hours based on the cell. Hope this helped
A chemical change must have occurred in investigation B step 2 because a change in color occurred.
<h3>What is a chemical change?</h3>
A chemical change is said to occur when a new substance has been formed. The markers of the occurrence of a chemical change are signs such as;
- Evolution of a gas
- Appearance of a solid
- Change of color
- Change of temperature
Now a physical change does not involve the formation of a new substance. Physical change would always involve the change of a substance from one form to another such as the melting of ice.
As such, in looking our for the steps in which a chemical change occurred we must look out for the properties of a chemical change as mentioned above.
Now, a chemical change must have occurred in investigation B step 2 because a change in color occurred.
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Missing parts;
Investigations were carried out in a science lab to explore the topic of chemical and physical changes. Investigation A Step 1. Add 5 tsp. salt to 100 ml warm water and stir until most or all of the salt is no longer visible. Step 2. Heat the salt solution on a burner until only a white solid remains. Investigation B Step 1. Mix 10 tsp. white sugar into 100 ml water and stir until most or all of the sugar is no longer visible. Step 2. Heat the sugar solution on a burner until the solution thickens and turns brown. In which step(s) did a chemical change most likely occur?
I just took the test. Edgen says the answer is c. suffocation.
Answer:
The correct option is D.
Explanation: The options attached to this question are given below:
A) Bacteria from other animals replace those killed by the antibiotics.
B) The few surviving bacteria that are affected by the antibiotics develop immunity to the antibiotics, which they pass on to their progeny.
C) The antibiotics cause new mutations to occur in the surviving bacteria, which results in resistance to antibiotics.
D) The antibiotics kill susceptible bacteria, but the few that are naturally resistant live and reproduce, and their progeny repopulate the host animal.
E) The antibiotics persist in soil and water.
Antibiotics are sometimes used in animals to control infections. With time, the microbes that are been targeted with the antibiotics usually develop mutations, which makes the antibiotics to become ineffective, thus, the antibiotics will only be able to kill the susceptible microbes while the ones that have developed resistance will remain and give birth to young ones that are also resistant to antibiotics.