What property is used to organize elements on the periodic table?

The atoms are both isotopes of calcium (atomic number 20). One isotope has a mass number of 40 (40Ca), which means it has 20 neutrons, while the other isotope has a mass number of 44 (44Ca), which means it has 24 neutrons.

When two different atoms have the same number of protons but different mass numbers, they are known as isotopes of the same element. In this case, since both atoms have 20 protons, they are isotopes of the element with the atomic number 20, which is calcium.

The identity of an atom is defined by its number of protons, which is the atomic number. For calcium, the atomic number is indeed 20. The mass number, which is given as 40 and 44 in the two variants, represents the total number of protons and neutrons in the nucleus. To find the number of neutrons in each isotope:

Therefore, the isotopes of calcium can be represented as 40Ca (20 protons and 20 neutrons) and 44Ca (20 protons and 24 neutrons).

Answer:

The mass of the rubbing alcohol is 14.77 g

Explanation:

The formula to be used here is that of density which is shown below

Density = Mass ÷ volume

The density of the rubbing alcohol (also known as isopropyl alcohol) is given in the question as 0.79 g/ml while the volume of same is given as 18.7ml. The mass of this rubbing alcohol is the unknown (which we can derive from the formula given earlier).

Hence,

Mass = Density × volume

Mass = 0.79 × 18.7

Mass = 14.77 g

Answer:

bottom left corner

Explanation:

These are where their located

The metals in the bottom left corner of the periodic table are the most active in the sense that they are the most reactive. For example, lithium, sodium, and potassium all react with water.

The periodic table is a tabular array of chemical elements organized by atomic number, beginning with hydrogen and progressing to oganesson, which has the highest atomic number.

An element's atomic number is the number of protons in the nucleus of an atom of that element. There is one proton in hydrogen and 118 in oganesson.

Caesium, the most reactive metal in the periodic table, reacts violently, which is why it cannot be demonstrated in a classroom. When other common metals, such as iron and copper, are dropped into water, they produce no reaction.

Thus, The most reactive metals in the bottom left corner of the periodic table.

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Answer:

Fluorine

Explanation:

Enzymes work by lowering the activation energy, making the reaction faster. They bind to reactants, presenting them in a manner that speeds up the bond breaking/formation. Enzymes don’t change the free energy; they only reduce the activation energy.

Enzymes work by lowering the activation energy of a chemical reaction, thus speeding up the reaction rate. Enzymes accomplish this by binding to the reactant molecules and positioning them in a manner that facilitates the bond-breaking and bond-forming processes more readily. They essentially act as catalysts within a cell.

The enzyme contains an active site that provides a unique chemical environment made up of amino acid R groups. This active site is perfectly suited to convert particular chemical reactants known as substrates into unstable intermediates called transition states. The binding of enzymes and substrates follow an induced-fit model, where the enzyme undergoes slight adjustments upon substrate contact, resulting in full, optimal binding.

Contrary to some misconceptions, enzymes don't alter the free energy of the reactants or the products. They only reduce the activation energy required for the reaction to proceed. After the reaction, the enzyme itself does not undergo any change and can participate in other reactions.

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The student's measurement is 13.486% less than the true value. The percent error is 13.486%.

Given information:

Measured value = 6.80 [tex]\rm \frac{g}{cm^3}[/tex]

True value = 7.86 [tex]\rm \frac{g}{cm^3}[/tex]

Percent error is a measurement of the discrepancy between an experimental or estimated value and a true or accepted value.

The percent error is calculated using the following formula:

[tex]\rm Percent \ error = |\frac{(measured \ value - true\ value)}{true \ value}| \times 100[/tex]

In this case, the measured value is 6.80 g/cm3 and the true value is 7.86 g/cm3. So, the percent error is:

[tex]\rm Percent \ error = |\frac{(6.80 - 7.86)}{7.86}| \times 100%[/tex]

Percent error = -13.486005089058532 %

The negative sign indicates that the measured value is less than the true value. So, the percent error is 13.486%. The student's measurement is 13.486% less than the true value.

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Final answer:

The percent error in the calculated density of iron compared to the actual value is approximately 13.49%. The correct density of iron is 7.86 g/cm³, which can be converted to 7860 kg/m³ for different unit requirements.

Explanation:

The student is asking how to calculate the percent error in the measured density of iron. The percent error can be found using the formula: percent error = |(experimental value - actual value) / actual value| × 100%.

In this case, the experimental value of density is 6.80 g/cm³ and the actual value from the handbook is 7.86 g/cm³. Plugging these values into the formula gives us: percent error = |(6.80 - 7.86) / 7.86| × 100% ≈ 13.49% (rounded to two decimal places).

To convert the correct density of iron from g/cm³ to kg/m³, multiply the density in g/cm³ by 1000 to convert grams to kilograms and by (100)^3 to convert cm³ to m³, resulting in 7.86 g/cm³ × 1000 kg/g × (100)^3 cm³/m³ = 7860 kg/m³.

Which of the following measurements is equal to 2.3 dL?

23 L

The correct measurement equal to 2.3 dL is 230,000 µL.

To find the equivalent measurement, we need to understand the relationship between different units of volume in the metric system. The prefixes used in the metric system are as follows:

- deci- (d) means one-tenth (1/10)

- centi- (c) means one-hundredth (1/100)

- milli- (m) means one-thousandth (1/1000)

- micro- (µ) means one-millionth (1/1000000)

Now, let's convert 2.3 dL to liters, then to centiliters, milliliters, and micro liters:

1. Since 1 deciliter (dL) is equal to 0.1 liters (L), we have:

[tex]\[ 2.3 \text{ dL} = 2.3 \times 0.1 \text{ L} = 0.23 \text{ L} \][/tex]

2. To convert liters to centiliters (cL), we know that 1 L is equal to 100 cL:

[tex]\[ 0.23 \text{ L} = 0.23 \times 100 \text{ cL} = 230 \text{ cL} \][/tex]

3. To convert liters to milliliters (mL), we know that 1 L is equal to 1000 mL:

[tex]\[ 0.23 \text{ L} = 0.23 \times 1000 \text{ mL} = 230 \text{ mL} \][/tex]

4. To convert liters to micro liters (µL), we know that 1 L is equal to 1,000,000 µL:

[tex]\[ 0.23 \text{ L} = 0.23 \times 1,000,000 \text{ µL} = 230,000 \text{ µL} \][/tex]

Given these conversions, we can now match the equivalent measurement to the options provided:

- 23 L is incorrect because 2.3 dL is equivalent to 0.23 L, not 23 L.

- 2,300 cL is incorrect because 2.3 dL is equivalent to 230 cL, not 2,300 cL.

- 23,000 mL is incorrect because 2.3 dL is equivalent to 230 mL, not 23,000 mL.

- 230,000 µL is correct because 2.3 dL is equivalent to 230,000 µL.

Therefore, the correct answer is 230,000 µL.

Answer:

flowers

rocks

blood

water

bacteria

sugar

skin

An ice water slush mixture is used to calibrate thermometers at 0°C because it guarantees the temperature stays constant due to the thermal equilibrium between the melting ice and water, providing a precise reference for calibration.

To calibrate a thermometer at 0°C, it is necessary to use an ice water slush mixture rather than just ice. The reason for this is that the mixture of ice and water will be in thermal equilibrium, ensuring that the temperature remains consistently at 0°C. This equilibrium state occurs because the melting ice absorbs heat without a change in temperature until it completely transitions to liquid water.

The presence of ice ensures that any heat added to the system does not increase the temperature but instead is utilized to change the phase of the ice to water. This phenomenon is why a cup of water with ice cubes remains at 0°C on a hot day and why it is essential for the mixture to have both ice and liquid water to create an accurate calibration point for the thermometer.

Final answer:

A physical change involves no bonds being broken or formed and the properties of the substances remain the same. Examples of physical changes include dissolving sugar in water and melting ice. A chemical change occurs when one or more substances change into different substances with different properties. Examples of chemical changes include burning wood and rusting of iron.

Explanation:

Physical Change

Physical changes are changes in which no bonds are broken or formed. This means that the same types of compounds or elements that were there at the beginning of the change are there at the end of the change. Because the ending materials are the same as the beginning materials, the properties (such as color, boiling point, etc.) will also be the same. Physical changes involve moving molecules around, but not changing them. Some types of physical changes include:

Chemical Change

Chemical changes occur when one or more substances change into different substances. During a chemical change, new substances are formed with different properties. Chemical changes are often harder to reverse than physical changes. Some examples of chemical changes include:

The green color copper turns when exposed to air is due to a chemical change. This happens because of a reaction between copper and the oxygen in the air, resulting in copper(II) oxide, or patina. The resulting green layer passivates, or protects, the copper from further corrosion.

The tendency of copper to turn green when exposed to air is a chemical change. This color change happens due to a chemical reaction between copper and the oxygen in the air, resulting in the formation of a new compound known as copper(II) oxide, which has a characteristic blue-green color, often referred to as patina. This green layer forms a protective barrier, preventing further corrosion of the underlying copper in a process known as passivation.

For instance, the iconic Statue of Liberty has a characteristic green color because it is made of copper, and the copper has reacted with the elements to form a patina or green covering. This is not merely a physical change, but a chemical reaction between copper and the elements in its surroundings.

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Answer:the answer is 2. he noticed that his flashlight stopped working

1. he suspected that the batteries could be dead

3. he replaces the batteries in the flashlight with new batteries

4.his flashlight works again. he writes a note to himself to buy extra batteries

Explanation:

The correct order of steps followed by Jason with respect to the scientific method would be 2, 1, 3, and 4.

The scientific method is a rational order to steps through which phenomena are understood. The steps are;

Thus, in the case of Jason:

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The process of early mineral formation involves their crystallization and settling, reducing their amount in the remaining magma. This changes the magma's composition, making it richer in lighter elements leading to the formation of different minerals.

The crystallization and settling of the earliest formed minerals is a process called fractional crystallization. This affects the composition of the remaining magma significantly. As the early forming minerals, usually heavier ones like olivine and pyroxene, crystallize, they often sink towards the bottom due to their higher density. This reduces the amount of these components in the remaining magma, essentially changing its composition. The leftover magma typically becomes gradually enriched in lighter elements, such as silicon, aluminum, potassium, and sodium, leading to the formation of different minerals such as feldspars and quartz.

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The crystallization and settling of early-formed minerals in magma lead to changes in the composition of the remaining melt, resulting in the formation of different igneous rock types.

The crystallization and settling of early-formed minerals within magma significantly influence the remaining melt's composition in a process known as fractional crystallization. As magma cools, minerals with higher melting points crystallize first, gradually removing them from the molten portion. These early crystallizing minerals, often denser than the remaining magma, tend to settle to the magma chamber's bottom.

This settling process results in the depletion of certain elements and compounds from the melt, making it more evolved or differentiated. The remaining magma continues to cool and may form late-crystallizing minerals with a composition reflecting this evolution. The end result is the formation of igneous rocks with distinct mineral compositions, influenced by the sequential crystallization and settling of minerals.

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Answer

79 ml

Explanation

You have 237 237 ml of​ ammonia, whose strength is​ 100%.

If you want to make it 75%, then;

let 75%  ⇒ 237 ml of ammonia and

   25% ⇒  x ml of water.

∴ x = (25% ×237) / 75%

       = 5,925/75

         = 79 ml of water.

0.1409 moles of propane (C3H8) are present in 6.2g of propane.

Atomic mass of propane is 44.1g

6.2g of C3H8 ( 1mol C3H8/44.1g C3H8 )

= 0.1409 mol C3H8.

Hence, option B is the answer.

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