Q: A sample of copper metal is heated from $25^\circ C$ to $75^\circ C$. If the mass of copper is 50 g and its specific heat is $0.385 \ \mathrm{J/g\cdot ^\circ C}$, how much heat is absorbed?

$q = 0.385 \times 50 \times (75-25) = 962.5 \ \mathrm{J}$

Question 1

Which of the following best describes a chemical property?

Accepted Answer

The ability of iron to rust when exposed to oxygen

Question 2

A sample of table salt (NaCl) is classified as which of the following?

Accepted Answer

A pure substance and a compound

Question 3

Which of the following is an example of a physical change?

Accepted Answer

Water boiling to form steam

Question 4

Which statement about elements and compounds is correct?

Accepted Answer

A compound always contains two or more elements chemically combined in a definite proportion by mass

Question 5

Which of the following best explains why it takes more heat to raise the temperature of 200 g of water by 10°C than 100 g of water by the same amount?

Accepted Answer

The amount of heat required is directly proportional to the mass of the substance, as shown by $q = sm\Delta t$

Question 6

Which of the following is a correct statement about the law of conservation of mass and energy?

Accepted Answer

In a chemical reaction, the total amount of mass and energy remains constant

Question 7

A student mixes sand and salt together in a beaker. Which statement best describes the resulting mixture?

Accepted Answer

It is a heterogeneous mixture because the components retain their individual properties and can be separated by physical means

Question 8

Which of the following is an example of an endothermic reaction?

Accepted Answer

Photosynthesis in plants, where energy is absorbed from sunlight

Question 9

A sample of copper metal is heated from $25^\circ C$ to $75^\circ C$. If the mass of copper is 50 g and its specific heat is $0.385 \ \mathrm{J/g\cdot ^\circ C}$, how much heat is absorbed?

Accepted Answer

$q = 0.385 	imes 50 	imes (75-25) = 962.5 \ \mathrm{J}$

Question 10

Which of the following best describes the difference between a crystalline solid and an amorphous solid?

Accepted Answer

A crystalline solid has a regular, repeating arrangement of particles, while an amorphous solid does not

Question 11

Which of the following is a chemical change that occurs in everyday life?

Accepted Answer

Milk turning sour due to bacterial action

Question 12

Which of the following best describes the particulate nature of matter?

Accepted Answer

Matter is composed of tiny particles such as atoms and molecules that are in constant motion

Question 13

A chemical equation is written as $2H_2O \rightarrow 2H_2 + O_2$. Which of the following statements is true?

Accepted Answer

Water is decomposed into hydrogen and oxygen gases

Question 14

Which of the following is a correct conversion between temperature scales?

Accepted Answer

$K = ^\circ C + 273.15$

Question 15

Which of the following best explains why gases can be compressed much more than solids or liquids?

Accepted Answer

The particles in a gas are far apart and move independently of each other

Question 16

Which of the following is an example of the law of multiple proportions?

Accepted Answer

Carbon and oxygen can form both CO and $CO_2$, with different ratios of carbon to oxygen

Question 17

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to the surroundings

Question 18

A beaker contains 100 g of water at $20^\circ C$. How much energy (in joules) is required to raise the temperature to $30^\circ C$? (Specific heat of water = $4.184 \ \mathrm{J/g\cdot ^\circ C}$)

Accepted Answer

$q = 4.184 	imes 100 	imes (30-20) = 4184 \ \mathrm{J}$

Question 19

Which of the following is NOT a characteristic of a chemical change?

Accepted Answer

A change in shape or size

Chapter 3: Matter and Energy – Foundations of Chemistry

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