A scientist is performing an experiment on a powder. Which of the following is a sign that a chemical change has definitely occurred during his experiment?The powder catches on fire.
The powder releases bubbles.
The powder heats up.
The powder breaks apart into smaller particles.

Answers

Answer 1
Answer: The powder catches fire. The rest of the choices pertains to physical changes on the powder. When the powder catches fire a chemical change happens. For example, if the powder is organic, carbon dioxide and water will result during the combustion. 
Answer 2
Answer:

Answer:

➢ⅇ powder catches on fire

....….that would be your answer

Explanation:

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An atom of oxygen is in an excited state. When an electron in this atom moves from the third shell to the second shell, energy is(1) emitted by the nucleus
(2) emitted by the electron
(3) absorbed by the nucleus
(4) absorbed by the electron

Answers

An atom of oxygen is in an excited state. When an electron in this atom moves from the third shell to the second shell, energy is emitted by the electron. Hence, option B is correct.

What is an atom?

 The smallest piece of stuff that still retains its characteristics is an atom. A gold atom, for instance, is the smallest piece of that element that will still retain all of gold's properties and behaviors. When an atom is disassembled into its component parts, the subatomic particles found inside each have special characteristics that are not at all similar to those of the element the atom represents. Protons, neutrons, and electrons are the three different subatomic particle kinds.

The electron that transitioned from a higher to a lower level felt the change in energy level. Since the nucleus is unaffected, its energy levels are unaffected as well. Since it requires more energy to keep an electron at a higher energy level than a lower one, the shift in energy levels indicates that the electron released some energy.

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The change in energy level was experienced by the electron that moved from a higher to a lower level. This does not affect the nucleus, so the nucleus itself does not change energy levels. It takes more energy to hold an electron at a higher than a lower energy level, so the change in energy levels means that some energy was released by the electron, and this is choice (2).

A geologist was looking at a newmineral they found. The mineral

sample was gray, non-metallic, had

density of 3.8 g/mL, and a volume

of 48.3 mL

Of the observed properties listed

below, which is considered to be an

extensive property?

A Gray

B Metallic

C Density

D Volume

Answers

Answer:

D. Volume

Explanation:

Properties mentioned in the question;

colour = gray

Nonmetallic

Density = 3.8 g/mL

Volume = 48.3 mL

Of the mentioned, which is extensive ?

Extensive properties are those properties that are proportional to the amount of substance present.

The correct option is D. Volume. The other properties do not change with increasing or decreasing amount of the mineral

Final answer:

Volume is considered to be an extensive property.

Explanation:

The extensive property out of the observed properties listed is volume. An extensive property is one that depends on the amount of a substance. In this case, the volume of the mineral sample is directly proportional to the amount of the sample, so it is considered an extensive property.

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Hydrocarbons are separated from each other by a process called cracking distillation. a. True
b. False

Answers

True, cracking distillation is one process used to break hydrocarbons into smaller and more useful parts. This is achieved by using high temperatures and pressures with a catalyst. The most common catalyst used are the zeolites.

Answer:

Correct answer is FALSE I just tested it and it came out right.

Explanation:

Write the net ionic equation for the following reaction:

AgC2H3O2(aq) + CaCl2(aq) →

Answers

Answer:

2Ag^+(aq) + 2Cl^-(aq) --------> 2AgCl(s)

Explanation:

The net ionic equation reflects the main reaction that occurred in the system. It tells you the most important reaction that took place.

If we first put down the balanced molecular equation for the reaction, we have;

CaCl2(aq) + 2 AgC2H3O2(aq) ---------> 2 AgCl(s) + Ca(C2H3O2)2 (aq)

The net ionic equation is;

2Ag^+(aq) + 2Cl^-(aq) --------> 2AgCl(s)

As this reaction takes place at higher temperatures, it is observed that the equilibrium shifts toward the products. The reaction is

Answers

As this reaction takes place at higher temperatures, it is observed that the equilibrium shifts toward the products. The reaction is an endothermic reaction since it requires energy for the reaction to proceed which describes an endothermic reaction.

The answer is: endothermic reaction.

This reaction is endothermic (enthalpy is higher than zero), which means that heat is added.  

According to Le Chatelier's principle when the reaction is endothermic heat is included as a reactant and when the temperature increased, the heat of the system increase, so the system consume some of that heat by shifting the equilibrium to the right, producing more products.

Write the formula of the following chemical compounds: i. Calcium phosphate ii. Ammonium carbonate

Answers

i - Ca3(PO4)2
ii- (NH4)2CO3