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Citrus2011 [14]
2 years ago
7

In this activity, several changes will be made to samples of matter. Your challenge will be to decide if the change is physical

or chemical. You will also have to defend your choice. Remember that when a physical change occurs to a substance, the identity of the substance and its physical properties do not change. However, when a chemical change occurs to a sample, the original material is converted to a new form of matter. This substance has a unique set of physical and chemical properties.
Write a summary paragraph discussing this experiment and the results. Use the following questions to help guide the content of your paragraph.

Submit your recorded observations for each step.
Step 1: Burning Candle - record the mass and write your observations

Step 2: Cooling Candle - record the mass and write your observations

Step 3: Tearing paper - record your observations

Step 4: Wet paper - record your observations

Step 5: Burning pieces of paper - record your observations

Step 6: Salt and water in test tube - record your observations

Step 7: Baking soda and vinegar - record your observations

Answer the following questions.
What is the difference between a physical change and a chemical change?
What kind of change occurred in each test? What evidence do you have to support your decision? Be brief, but be sure to defend your conclusion with data.
Chemistry
1 answer:
Rus_ich [418]2 years ago
8 0

Answer:

Step 1: Burning Candle - Mass- 2.19 The wick of the candle changed colors, from white to black. The shape and height of the candle changed.

Step 2: Cooling Candle - Mass- 2.18, The shape of the has a flat surface.

Step 3: Tearing paper - The paper is somewhat easy to tear, and its edges change shape. It does take a bit to tear it into pieces though.

Step 4: Wet paper - It absorbed the water easily. It became very fragile.

Step 5: Burning pieces of paper - The paper burned fast, it changed color and folded inward and downward.

Step 6: Salt and water in test tube - The water changed color and even bubbled. Small particles of salt dissolve.

Step 7: Baking soda and vinegar - The substance bubbled and changed to a white yet somewhat transparent color.

In chemical changes, composition is the factor that changes, and it's sometimes harder to identify a chemical change as it can't always be seen. Whereas physical changes are more easily identifiable because they include smell, color, anything to do with appearance.

In the candle tests, it was a physical change because its physical appearance changed, such as its height, mass, and color of the wick. The tearing paper test was a physical change too because its physical appearance changed. It’s shape being the main change. I think the burning the paper was both physical and chemical because its physical appearance, the color and shape, changed. But the properties of it changed too, because it went from being paper to being ashes. The salt & water and the baking soda & vinegar were both chemical changes because some properties changed and they formed new substances. Both things caused a gas like substance to form which caused the bubbling formation of both.

Explanation:

..........

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A gas cylinder filled with nitrogen at standard temperature and pressure has a mass of 37.289 g. The same container filled with
andrew-mc [135]

Answer:

Molar mass = 3.9236 g/mol ≅ 4 g/mol

This corresponds to Helium gas.

Explanation:

Let the moles of nitrogen gas = x moles

Moles of carbon dioxide = x moles ( As both are filled at same temperature and pressure conditions )

Given:

Mass_{Container}+Mass_{Nitrogen\ gas}=37.289\ g

Molar mass of nitrogen gas, N_2 = 28.014 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

x\ moles= \frac{Mass}{28.014\ g/mol}

Mass of nitrogen gas = 28.014x g

So,

Let, Mass_{Container}=y

y+28.014x=37.289

Similarly,

Mass_{Container}+Mass_{Carbon\ dioxide\ gas}=37.440\ g

Molar mass of nitrogen gas, CO_2 = 44.01 g/mol

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

x\ moles= \frac{Mass{44.01\ g/mol}

Mass of nitrogen gas = 44.01x g

So,

y+44.01x=37.440

Solving the two equations, we get :

Mass_{Container}=y=37.025\ g

x = 0.00943 moles

Thus, Given:

Mass_{Container}+Mass_{Unknown\ gas}=37.062\ g

37.025\ g+Mass_{Unknown\ gas}=37.062\ g

Mass of the gas = 0.037 moles

Moles = 0.00943 moles

The formula for the calculation of moles is shown below:

moles = \frac{Mass\ taken}{Molar\ mass}

Thus,

0.00943\ moles= \frac{0.037\ g}Molar mass}

Molar mass = 3.9236 g/mol ≅ 4 g/mol

This corresponds to Helium gas.

7 0
2 years ago
A sample of element X contains 90% X-35 atoms, 8.0% X-37 atoms, and 2.0% X-38 atoms. The average atomic mass will be closest to
Ne4ueva [31]

To find average atomic mass you multiply the mass of each isotope by its percentage, and then add the values up.

35 * 0.90 + 37 * 0.08 + 38 * 0.02 = 35.22

Average atomic mass closest to 35.22 amu.

6 0
2 years ago
Read 2 more answers
What is the pH of a solution of 0.400 M CH₃NH₂ containing 0.250 M CH₃NH₃I? (Kb of CH₃NH₂ is 4.4 × 10⁻⁴)
Karolina [17]

Answer:

\boxed{\text{10.84}}

Explanation:

A solution of a weak base and its conjugate acid is a buffer.

The equation for the equilibrium is

\rm CH$_3$NH$_2$ + H$_2$O $\, \rightleftharpoons \,$ CH$_3$NH$_2$+ H$_{3}$O$^{+}$\\\text{For ease of typing, let's rewrite this equation as}\\\rm B + H$_2$O $\longrightarrow \,$ BH$^{+}$ + OH$^{-}$; $K_{\text{b}}$ = 4.4 \times 10^{-4}$

The Henderson-Hasselbalch equation for a basic buffer is

\text{pOH} = \text{p}K_{\text{b}} + \log\dfrac{[\text{BH}^{+}]}{\text{[B]}}

Data:

   [B] = 0.400 mol·L⁻¹

[BH⁺] = 0.250 mol·L⁻¹

    Kb = 4.4 × 10⁻⁴

Calculations:

(a) Calculate pKb

pKb = -log(4.4× 10⁻⁴)  = 3.36

(b) Calculate the pH

\text{pOH} = 3.36 + \log \dfrac{0.250}{0.400} = 3.36 + \log 0.625 = 3.36 - 0.204 = 3.16\\\\\text{pH} =14.00 -3.16 = \mathbf{10.84}\\\\\text{The pH of the solution is }\boxed{\textbf{10.84}}

4 0
2 years ago
At one point in the video, someone is balancing a chemical reaction. The person writes a coefficient of 2 in front of Fe2O3 but
mario62 [17]

answer: the 4 is the product and the other numbers are reactants

Explanation:

i’m pretty sure that’s the answer . i did this last week :)

8 0
2 years ago
How much silver can be produced from 125g of Ag2S
rosijanka [135]

Answer:

108.9g of Silver can be produced from 125g of Ag2S

Explanation:

The compound Ag2S shows that two atoms of Silver Ag, combined with an atom of Sulphur S to form Ag2S. We can as well say the combination ration of Silver to Sulphur is 2:1

•Now we need to calculate the molecular weight of this compound by summing up the molar masses of each element in the compound.

•Molar mass of Silver Ag= 107.9g/mol

•Molar mass of Sulphur S= 32g/mol

•Molecular weight of Ag2S= (2×107.9g/mol) + 32g/mol

•Molecular weight of Ag2S= 215.8g/mol + 32g/mol= 247.8g/mol

•From our calculations, we know that 215.8g/mol of Ag is present in 247.8g/mol of Ag2S

If 247.8g Ag2S produced 215.8g Ag

125g Ag2S will produce xg Ag

cross multiplying we have

xg= 215.8g × 125g / 247.8g

xg= 26975g/247.8

xg= 108.85g

Therefore, 108.9g of Silver can be produced from 125g of Ag2S

3 0
2 years ago
Read 2 more answers
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