A blacksmith melts and shapes a block of iron into a blade. She then sets the blade, whose edges are molten, outside, where it is raining slightly. The blade's outer edges both solidify and then rust. Which of the following has happened to the iron throughout the day? a. The iron has undergone a physical change only. b. The iron has undergone a chemical change only. c. The iron has undergone both a physical and chemical change. d. The iron has not undergone any changes.

atoms are always in motion. i took the test and got it correct

Answer:

The correct answer is (D) Atoms are always in motion is not a part of Dalton's atomic theory because Dalton never sated about atomic motion in his atomic theory. Other options are the part of Dalton's atomic theory.

Explanation:

According to Dalton's atomic theory:

1. Every element is made up of tiny atoms.

2. The atom of the same element shares the same property.

3. The atoms of different elements differ in properties.

4. Atoms cannot be seen and are indestructible.

Dalton never describe the motion of atoms in his theory

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A pure substance is a sample of matter with a constant composition and with all specimens possessing the exact same properties. Pure substances can either be elements, with only one type of atom, or compounds, composed of two or more types of atoms.

A sample of matter is considered a pure substance when it has a constant composition and all specimens have exactly the same properties. Pure substances can be classified into two categories: elements and compounds. Elements are pure substances that consist of only one type of atom and cannot be broken down by a chemical change while compounds are pure substances that consist of two or more types of atoms. For instance, any sample of sucrose (table sugar) is a pure substance consisting of 42.1% carbon, 6.5% hydrogen, and 51.4% oxygen by mass, having the same physical properties like melting point, color, and sweetness, irrespective of its source.

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The answer to your question is (B) because it does requires the least amount of force for the bicycle to climb the hill.

One mole of any substance is equal to Avogadro’s number, 6.023 x 10²³  

A mole of magnesium = a mole of iron = Avogadro’s number, 6.023 x 10 ²³

One mole of any element contains 6.023 x 10²³ number of atoms.  

One mole of any substance contains 6.023 x 10²³ number of atoms, molecules, ions, or formula units.

Answer : Option A) independent variable.

Explanation : The dark closet (N) was a part of independent variable as it's variable does not depends on any other variable.

Also, growth factor which was the major aim of study was the dependent variable as it was dependent on closet where it was placed.

Constant was the water as the quantity of water was same for both the plants.

Control was the plant that was used for this experiment, as this was the standard that was used for the comparison of the growth.

The main ideas in Dalton's atomic theory are: all atoms of a given element have the same mass and other properties, each element is composed of tiny, indestructible particles called atoms, and atoms combine in simple, whole-number ratios to form compounds.

The main ideas in Dalton's atomic theory are:

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About 10% of the energy at one trophic level is transferred to the next, with the rest being used for metabolism or lost as heat, explaining why there are typically no more than four trophic levels in a food chain. Hence option A is correct.

The figure that represents the percent of energy transferred from one trophic level to the next is generally about 10%. Energy is passed up a food chain or web from lower to higher trophic levels, and it is depicted by an energy pyramid. The other 90% of the energy is used for metabolic processes or given off to the environment as heat. This significant loss of energy at each step explains why typically there are no more than four trophic levels in a food chain or web, because there isn't enough energy left to support more levels.Hence option A is correct.

First convert mass to number of moles. Molar mass of H2C2O2 • 2H2O = 94 / mol

1.89g / (94 g / mol) = .02 mol H2C2O2 • 2H2O

Then we divide by 0.1 L, or 100 mL, and we get a concentration of 0.2 M.

Since there are two positive ions (2 H+), therefore normality is:

0.4 N

Answer:

CH2

Explanation:

Divide by 2 and you get the answer

Explanation:

When zinc chemically reacts with hydrochloric acid in chemical reaction then it leads to the formation of zinc chloride along with evolution of hydrogen gas.

Chemical equation which represents this chemical reaction is as follows.

        [tex]Zn + HCl \rightarrow ZnCl_{2} + H_{2}[/tex]

Number of atoms on reactant side are as follows.

Zn = 1

H = 1

Cl = 1

Number of atoms on product side are as follows.

Zn = 1

H = 2

Cl = 2

Hence, to balance this equation we will multiply HCl by 2 on reactant side. Therefore, the balanced chemical equation is as follows.

              [tex]Zn + 2HCl \rightarrow ZnCl_{2} + H_{2}[/tex]

Answer:

Independent: exercise.

Dependent: concentration.

Explanation:

Hello,

In this case, as the statement says that the experiments is towards the effects of the exercise on concentration it is clear that the independent variable is the exercise as the concentration depends on the performed exercise. Therefore, the dependent variable is the concentration as it changes as a function of the specified exercise.

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In water Sodium carbonate dissociates to form Sodium hydroxide and carbon dioxide.

The dissociation reaction for Sodium carbonate is

[tex]\rm \bold{ Na_2CO3 \rightarrow 2 Na^(^+^) + CO_3^(^2^-^)}[/tex]

In water the sodium ion will react with [tex]\rm \bold {OH^-}[/tex] ion of water to form Sodium Hydroxide.

[tex]\rm \bold{ Na_2CO3_(_a_q_)+H_2O \rightarrow 2 NaOH + CO_2}[/tex]

Hence we can conclude that in water, Sodium carbonate dissociates to form Sodium hydroxide and carbon dioxide.

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In a neutral atom, the number of protons equals the atomic number, which also indicates the same number of electrons.

For a neutral atom, the number of protons is also equal to the atomic number. Atoms are neutral in electrical charge because they have the same number of negative electrons as positive protons. Therefore, the atomic number of an atom also tells you how many electrons the atom has. For instance, hydrogen has an atomic number of 1, which means it has 1 proton and 1 electron. Manganese, with an atomic number of 25, has 25 protons and also 25 electrons when neutral. The atomic number not only signifies the number of protons in an atom but also, by default, the number of electrons in a neutral atom.

The ability to react with acid is a type of chemical property, therefore the correct answer is option C.

A chemical reaction is a process in which one or more substances, also known as reactants are converted to one or more different substances, known as products.

There are differences between the chemical and physical properties of any material.

The ability to react with acid is a type of chemical property,

While on the other hand ability to conduct heat, the ability to become magnetic, and the ability to conduct electricity are the physical properties of any material.

Thus, the ability to react with acid is a type of chemical property the correct answer is option C.

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Answer:

Aluminium reacts with dilute sulfuric acid based on the following reaction:

2Al + 3H2SO4 ..............> Al2 (SO4)3 + 3H2

From the periodic table:

mass of aluminium = 27 grams

mass of hydrogen = 1 gram

mass of oxygen = 16 grams

mass of sulfur = 32 grams

Therefore:

molar mass of aluminium = 27 grams

molar mass of sulfuric acid = 2(1) + 32 + 4(16) = 98 grams

From the balanced chemical equation:

2 moles of aluminium react with 3 moles of dilute sulfuric acid.

This means that 34 grams of Al react with 294 grams of the acid

To get the amount  of aluminium that reacts with 5.890 g of sulfuric acid, we will do cross multiplication as follows:

amount of Al = (5.890 x 34) / 294 = 0.6811 grams

Explanation:

Answer:

physcial chemist

Explanation:

k12 user. for all of those who understand nothing about this quiz.

As water freezes or evaporates, the salinity of the remaining ocean water increases. This is due to the separation of pure water molecules from the dissolved ions during both evaporation and the crystallization process of freezing, leaving behind a higher concentration of salts in the water.

When water freezes or evaporates, the salinity of the remaining ocean water increases. During the process of evaporation, only the water molecules transition from a liquid state to gas and subsequently condense to form clouds, leaving the dissolved ions like salt behind. This concentration effect also occurs when water freezes. Ice crystallizes and incorporates very little of the dissolved salts, thus also leaving behind more concentrated salty water.

In the context of desalination, one can observe how these natural processes of phase change can separate the water from its dissolved substances. While the evaporative process is a distillation that produces almost pure water, the freezing process excludes salts from the solid ice phase. As a result, methods such as evaporation, condensation, and freezing are employed to purify water and reduce its salinity.

Moreover, in temperature dynamics during the freezing of water, the heat released keeps the temperature steady at the melting point while the rest of the water turns into ice. This phenomenon has implications for the thermodynamic properties of water and how such changes affect the surrounding environment.