True or false: scientists make observations very carefully science

Tell me what happens during Observing a chemical change

worty [1.4K]

Explanation:

Gas bubbles can appear, there may be a color change, there may be a temperature change, there could be the production of light, volume change, change in smell or taste, or formation of a precipitate.

In a chemical change, atoms react with each other to form a new substance/product.

6 0

3 years ago

During an experiment, 575 mL of neon gas at 101 kPa were compressed in a cylinder to a volume of 144 mL.

Ne4ueva [31]

Answer:

403.3 kPa is the new pressure

Explanation:

This problem is solved by this formula:

P₁ . V₁ = P₂ . V₂

101kPa . 575 mL = P₂ . 144mL

(101kPa . 575 mL) / 144 mL = P₂

403.3 kPa = P₂

8 0

3 years ago

Which of the following is a polar molecule?

mixer [17]

the answer is option b

7 0

3 years ago

When cream mixes with coffee, is this a chemical or physical change?

svlad2 [7]

It is a physical change when cream mixes with coffee, it changes the color of the coffee. When you add more or less cream there is a color change depending on the consistency of cream. The properties are not changes and a no new compound is formed as in chemical change with a reaction of two compounds, a new compound is formed with different properties. So it is a physical change.

7 0

2 years ago

Why is a homogeneous mixture not considered a pure substance? Question 6 options: A pure substance can be separated by physical

krok68 [10]

1. Why is a homogeneous mixture not considered a pure substance?

Answer:

A pure substance can be separated by chemical means, while a mixture can be separated by physical means.

2. What is true if mass is conserved in a reaction?

Answer:

There are equal numbers of atoms on both sides.

3. Methane reacts with oxygen then what are the products?

Answer:

carbon dioxide and water

4. Which one of the following is not a homogeneous mixture?

Answer:

vegetable soup

5. The substance is not uniform in appearance and each part of the mixture contains a combination of different ingredients in different ratios.

Answer:

heterogeneous mixtures

6. If a solution is saturated, which of these is true?

Answer:

More solvent can be dissolved

7. Which of these substances are molecules?

Answer:

All compounds are molecules but not all molecules are compounds. Molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. So correct option is 3 and 4.

8. What makes a solution a homogeneous mixture?

Answer:

It is uniform in composition.

9. When a solute is added to a solution, why does it remain homogeneous?

Answer:

The solute dissolves.

10. The chemical formula of glucose is C6H12O6, so it is classified as a(n)

Answer:

pure substance.

11. How many chlorine (Cl) atoms would be in 4 molecules of salt (4 NaCl)?

Answer:

4

12. In a solution of salt and water, which component is the solute?

Answer:

Salt

13. These substances are all H2O2, Li , NaCl , O2

Answer:

Pure Substances

14. If you have 5 grams of product after a chemical reaction, how many grams of reactants did you have at the start of the reaction?

Answer:

5

15. What is the difference between a compound and a mixture?

Answer:

A compound is a pure substance, but a mixture is not.

16. A firework exploding would be an example of a(n) ________.

Answer:

Exothermic reaction

17. If Lavoisier heated 100 grams of powdered mercuric oxide to produce 93 grams of liquid mercury, how much oxygen would be released?

Solution

2HgO ==> 2Hg + O2

Mass of HgO = 100 g

Molar mass of HgO = 216.59 g/mol

Moles = mass/molar mass = 0.46 moles

From balance chemcial equation

HgO : O2

2 = 1

0.46 = (1 × 0.46 ) ÷ 2 = 0.23 moles

mass of O2 = moles× molar mass = 0.23 × 32 = 7.36 g

18. Using the Law of Conservation of Matter, determine the number of grams of iron sulfide (FeS) that will be produced in this reaction.

Solution

12g Fe + 64g S → _____ g FeS

According to Law of Conservation of Matter, The total mass of reactant is equal to total mass of product , so the number of grams of iron sulfide (FeS) that will be produced in this reaction as follow.

12 + 64 = 76 g of FeS

Hope this Help.

3 0

3 years ago

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