Q: A sample of iron is heated from $$25\ ^\circ\mathrm{C} to$$ $$75\ ^\circ\mathrm{C}. If $$the mass of the iron is $$50\ \mathrm{g}$$ and the specific heat of iron is $$0.452\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$, how much heat (in joules) is absorbed by the iron?

$$q = 50 \times (75-25) \times 0.452 = 1130\ \mathrm{J}$$

Q: A 100 g sample of water is heated from $$20\ ^\circ\mathrm{C} to$$ $$80\ ^\circ\mathrm{C}. $$The specific heat of water is $$4.18\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}. $$How much heat is absorbed?

$$q = 100 \times (80-20) \times 4.18 = 25080\ \mathrm{J}$$

Q: A 25 g sample of a metal absorbs $$200\ \mathrm{J} of $$heat, causing its temperature to increase from $$20\ ^\circ\mathrm{C} to$$ $$40\ ^\circ\mathrm{C}. $$What is the specific heat of the metal?

$$SH = \dfrac{200}{25 \times (40-20)} = 0.4\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$

Question 1

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more different elements in a fixed ratio that can be separated into simpler substances by chemical means.

Question 2

Which of the following is an example of a heterogeneous mixture?

Accepted Answer

A chocolate chip cookie

Question 3

Which statement about elements is correct?

Accepted Answer

Elements are the fundamental building blocks that make up all matter.

Question 4

A sample of iron is heated from $$25\ ^\circ\mathrm{C} to$$ $$75\ ^\circ\mathrm{C}. If $$the mass of the iron is $$50\ \mathrm{g}$$ and the specific heat of iron is $$0.452\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$, how much heat (in joules) is absorbed by the iron?

Accepted Answer

$$q = 50 	imes (75-25) 	imes 0.452 = 1130\ \mathrm{J}$$

Question 5

Which of the following is a chemical property?

Accepted Answer

Flammability

Question 6

A student dissolves sugar in water. Which type of change is this, and why?

Accepted Answer

Physical change, because the sugar and water can be separated by evaporation.

Question 7

Which of the following statements about the states of matter is correct?

Accepted Answer

Solids have a definite volume and maintain their shape regardless of the container.

Question 8

Convert a temperature of $$68\ ^\circ\mathrm{F} to $$Celsius using the correct formula.

Accepted Answer

$$T_\mathrm{C} = \dfrac{68 - 32}{1.8} = 20\ ^\circ\mathrm{C}$$

Question 9

Which of the following best illustrates the law of conservation of energy?

Accepted Answer

A ball at the top of a hill has potential energy that is converted to kinetic energy as it rolls down.

Question 10

A 100 g sample of water is heated from $$20\ ^\circ\mathrm{C} to$$ $$80\ ^\circ\mathrm{C}. $$The specific heat of water is $$4.18\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}. $$How much heat is absorbed?

Accepted Answer

$$q = 100 	imes (80-20) 	imes 4.18 = 25080\ \mathrm{J}$$

Question 11

Which of the following is a correct statement about mixtures?

Accepted Answer

Mixtures can be separated into their components by physical means.

Question 12

Which of the following is a physical property?

Accepted Answer

Boiling point

Question 13

A 25 g sample of a metal absorbs $$200\ \mathrm{J} of $$heat, causing its temperature to increase from $$20\ ^\circ\mathrm{C} to$$ $$40\ ^\circ\mathrm{C}. $$What is the specific heat of the metal?

Accepted Answer

$$SH = \dfrac{200}{25 	imes (40-20)} = 0.4\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$

Question 14

Which of the following is a correct conversion for nutritional Calories?

Accepted Answer

$$1\ \mathrm{Cal} = 1000\ \mathrm{cal}$$

Question 15

Which of the following best describes potential energy?

Accepted Answer

The energy stored due to an object's position or composition

Question 16

A sample of gold (specific heat $$0.129\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}) $$and a sample of water (specific heat $$4.18\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}) $$are both heated by the same amount of energy. Which will experience the greater temperature change, assuming equal masses?

Accepted Answer

The gold, because it has a lower specific heat.

Question 17

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

Accepted Answer

Paper burning to produce ash and gases

Question 18

A 10 g sample of a substance at $$25\ ^\circ\mathrm{C}$$ absorbs $$420\ \mathrm{J} of $$heat and its temperature rises to $$45\ ^\circ\mathrm{C}. $$What is the specific heat of the substance?

Accepted Answer

$$SH = \dfrac{420}{10 	imes (45-25)} = 2.1\ \mathrm{J}/\mathrm{g}\ ^\circ\mathrm{C}$$

Chapter 3: Matter and Energy – Introduction to Chemistry Study Notes

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