1: Which of the following is the best example of a valid hypothesis?A. Children like brand X peanut butter better than brand Y peanut butter.
B. If I add substance X, then it will lower the temperature at which water freezes.
C. People should eat vegetables.
D. Bananas are better for you than chocolate. 2: Kobe is testing whether 100 g of substance A, 100 g of substance B, or 100 g of substance C produces more oxygen in a chemical reaction at 25°C. What is the independent variable?
A. the masses of the substances
B. the temperature of the substances
C. the amount of oxygen produced
D. the nature of the substances 3: A chemist measures the amount of mercury in sediment samples from three areas of a river (the source, the midway point, and the mouth). Which of the following is the most reasonable hypothesis for the chemist's experiment?
A. If a chemical plant near the source of the river is dumping mercury, then the mercury levels should be highest at the source and lowest at the mouth.
B. If a chemical plant near the source of the river is dumping mercury, then the mercury levels should be highest at the mouth and lowest at the midway point.
C. If a chemical plant near the source of the river is dumping mercury, then the mercury levels should be highest at the mouth and lowest at the source.
D. If a chemical plant near the source of the river is dumping mercury, then the mercury levels should be the same all along the river.

Answers

Answer 1

Answer: Below are the answers:

1. The best example of valid hypothesis is B which is "If I add substance X, then it will lower the temperature at which water freezes."

2. The answer for number 2 is D which is "the nature of the substances"

3. Its B which is " If a chemical plant near the source of the river is dumping mercury, then the mercury levels should be highest at the mouth and lowest at the midway point."

Answer 2

Answer:

The correct options are as follows:

1. B.

In scientific investigation, an hypothesis refers to a supposition that is put forward to explain an observed phenomenon. A hypothesis is described as valid if it fulfilled five different conditions. The conditions are as follows:

1. It must be capable of empirical verification.

2. It must be express clearly and it must be definite and certain.

3. It must be specific and it is predictions must be clearly expressed.

4. It must be formulated in such a way that its content can easily be translated to understand the observed phenomenon that give birth to the hypothesis.

5. It should possess theoretical relevance.

2. D.

Scientific investigations usually make use of two major variables, these are dependent variables an independent variables. The dependent variable refers to the variable whose value depend on that of another variable. The independent variable on the other hand refers to that variable whose variation does not depend on the value of another variable. In the question given above, the natures of the three substances is the independent variable because their variation is not determined by any variable.

3. B.

If a chemical plant near the source of a water body is dumping mercury inside the water, then the highest amount of mercury will be found at the mouth of the river while the lowest quantity of mercury will be found at the middle of the water. This is because as the water waves are carrying the mercury deposits away from the mouth of the river, they will disperse it evenly in the river and thus its concentration will reduce compare to that present at the mouth of the river. The highest amount of mercury is found at the mouth of the river because that is where the mercury enters the water.

Answer:

D) The geosphere, hydrosphere, and atmosphere

Explanation:

During the carbon cycle, various processes move carbon from the geosphere to the atmosphere such as volcanic eruptions release carbon dioxide from molten rock beneath the earth's surface to the atmosphere. Carbon can leave the soil through soil respiration which releases CO2, or by erosion which can carry it into rivers or the ocean, where it then enters the hydrosphere. Carbon is found in the hydrosphere dissolved in ocean water and lakes and hence the cycle continues.

The carbon cycle is the biogeochemical cycle which involves an exchange of carbon among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Carbon is the most important component of the biological compounds such as limestone. Also, during soil respiration, Carbon can leave the soil through it which releases $CO_(2)$ , which carries it into the rivers or the ocean, where it then enters the hydrosphere.

Thus, option D is correct.

How is controlling the rate of a chemical reaction useful to a chemical engineer, physician and chef?

Answers

It should be noted that controlling the rate of a chemical reaction is useful to the professions to improving production.

What is a chemical reaction?

It should be noted that a chemicalreaction simply means the process by which substances are converted to another substance.

In this case, controlling the rate of a chemical reaction is useful to the professions to improving production.

By finding out how fast products are made, one can develop methods to into such production.

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Controlling the rate of chemical reactions is crucial to a chef because that is what gives food its flavor. Bread that rises too fast or slow (yeast cells converting glucose into carbon dioxide) will taste awful compared to correctly risen bread. Flambé undergoes a very fast, but brief, chemical reaction when the alcohol in which it is smothered is ignited, caramelizing the creme on top. A slow reaction would melt it all, while an even faster reaction could cause the dish to explode.

Chemistry is best defined as the study of what

Answers

the science that systematically studies the composition, properties, and activity of organic and inorganic substances and various elementary forms of matter.

basically studying chemicals

Final answer:

Chemistry is the study of the properties, composition, and structure of substances, and the transformations they undergo. It also deals with the energy exchanges in these processes. As "The Central Science", chemistry interrelates with numerous other scientific disciplines.

Explanation:

Chemistry, often referred to as "The Central Science", is a branch of science that deals with the properties, composition, and structure of substances (defined as elements and compounds), the transformations they undergo, and the energy that is released or absorbed during these processes. It plays a vital role in multiple disciplines such as biology, medicine and environmental science. It allows us to understand the makeup of substances, from the atomic level to complex molecules, and how they interact through chemical reactions.

One example of a branch of Chemistry is thermochemistry, which focuses on relationships between heat, work, and other types of energy in physical and chemical processes. Dalton's atomic theory, investigating quantitative and qualitative aspects of chemistry, also developed the concept of atomic mass units, allowing for the calculation of formula mass and the quantitative description of substances.

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Which physical change is endothermic?(1) CO2(s)-->CO2(g) (3) CO2(g)-->CO2(l)
(2) CO2(l)-->CO2(s) (4) CO2(g)-->CO2(s)

Answers

Answer: The correct option is 1.

Explanation:Endothermic reactions are the reactions in which heat is provided to break down the reactant molecules.

In option 1:

The stronger intermolecular forces between the particles in solid molecule are broken down to convert into gaseous form. Hence, some energy in the form of heat is provided to move them far apart. Therefore, it is considered as an endothermic reaction.

In option 2, 3 and 4:

All the other processes involves the formation of bonds and thus there is no need to provide any energy.

The physical change that is endothermic is $\boxed{\left( 1 \right){\text{ C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)}$ .

Further explanation:

Changes are of two types:

(A) Physical changes:

It is the process in which the physical properties of the system are affected. These changes can also be reversed by physical methods. In these kinds of changes, the molecular composition of the substance remains the same. These are reversible in nature and no new substances are formed. For example, boiling of water, chopping of wood, melting of wax are physical changes.

(B) Chemical changes:

In this change, new substances are formed by the chemical combination of the previous substances. The chemical properties of substance changes when it undergoes a chemical change. These are irreversible in nature. For example, fermentation of grapes, burning of wood, rusting of iron are chemical changes.

Endothermic reactions are those in which more energy needs to be supplied to the system than that released by it.

Exothermic reactions are those in which more energy is released by the system than that supplied to it.

(1) ${\text{C}}{{\text{O}}_{\text{2}}}\left( s \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( g \right)$

In this reaction, solid carbon dioxide is converted into gaseous carbon dioxide. The strong intermolecular force of attraction in solid needs to be broken down and energy is supplied for this purpose. Hence this is an endothermic process.

(2) ${\text{C}}{{\text{O}}_{\text{2}}}\left( l \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)$

In this reaction, liquid carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in liquid molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(3) ${\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( l \right)$

In this reaction, gaseous carbon dioxide is converted into liquid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in liquid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

(4) ${\text{C}}{{\text{O}}_{\text{2}}}\left( g \right) \to {\text{C}}{{\text{O}}_{\text{2}}}\left( s \right)$

In this reaction, gaseous carbon dioxide is converted into solid carbon dioxide. The intermolecular forces in gas molecules are weaker than that present in solid molecules and are broken down easily so energy is released during the process. Hence this is an exothermic process.

Learn more:

1. Which of these is an extensive property? brainly.com/question/1398514

2. Which of the phase changes is an exothermic change? brainly.com/question/1875234

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Physical and chemical changes

Keywords: physical change, chemical change, CO2, endothermic, exothermic, solid, liquid, gaseous, intermolecular forces, strong, weaker.

How many moles of CaO form when 98.60 g CaCO3 decompose

Answers

The balanced reaction is:

CaCO3 = CaO + CO2

We are given the amount of CaCO3 to decompose when heated. This will be our starting point.

98.60 g CaCO3 ( 1 mol CaCO3 / 100.09 grams CaCO3) (1 mol CaO / 1 mol CaCO3 ) ( 56.08 g O2 / 1 mol CaO) = 55.25 g CaO

0.9851mol. This is the rt answer just did it

Identify the following as a compound or a mixture: quartz (SiO2)

Answers

quartz (SiO2) is a compound. A compud is the combination of two or more elements. It is a compound because three elements are formed, the silicon and the two atoms of oxygen.

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