1.
When you cook pasta, you add salt to the water because:
Correct Answer
B. Because it raises the boiling point of the water, so that it will be hotter when it boils and the pasta will cook faster.
Explanation
Adding salt to the water when cooking pasta raises the boiling point of the water. This means that the water will reach a higher temperature before it boils, allowing the pasta to cook faster. The higher temperature also helps to ensure that the pasta cooks evenly and thoroughly. Therefore, adding salt to the water has a practical effect on the cooking process, rather than just being for taste.
2.
The relative randomness of molecules in the states of matter is best indicated by:
Correct Answer
D. gas > liquid > solid
Explanation
The correct answer is gas > liquid > solid. This is because gas molecules have the highest amount of kinetic energy and are able to move freely and randomly. Liquid molecules have less kinetic energy and are more confined in their movement compared to gas molecules. Solid molecules have the least amount of kinetic energy and are tightly packed together, resulting in less randomness in their movement.
3.
Which statement is true concerning solids
Correct Answer
C. A crystalline solid has an ordered structure, while an amorpHous solid has no ordered arrangement.
Explanation
A crystalline solid has an ordered structure, while an amorphous solid has no ordered arrangement. This means that in a crystalline solid, the atoms, ions, or molecules are arranged in a regular, repeating pattern, giving the solid a distinct shape and structure. On the other hand, in an amorphous solid, the atoms, ions, or molecules are randomly arranged, resulting in a lack of a specific shape or structure. This difference in arrangement affects the physical properties of the solids, such as their melting and boiling points.
4.
The state of matter that has
no definite size or shape is
Correct Answer
C. gas
Explanation
Gas is the state of matter that has no definite size or shape. Unlike solids and liquids, gases do not have a fixed volume or shape and can expand to fill the space available to them. Gas particles are in constant random motion and are not held together by strong forces, allowing them to move freely and occupy any space.
5.
The changing of a solid to a
liquid is called
Correct Answer
A. melting
Explanation
The process of changing a solid into a liquid is known as melting. During melting, the solid absorbs heat energy, causing the particles to gain enough energy to break their rigid structure and transition into a more fluid state. This results in the solid turning into a liquid.
6.
What happens during evaporation?
Correct Answer
C. A liquid changes to a gas
Explanation
During evaporation, a liquid changes to a gas. This process occurs when the molecules of a liquid gain enough energy to break free from their bonds and escape into the surrounding atmosphere. As the liquid molecules gain energy, they move faster and collide with each other, eventually breaking free and becoming a gas. Evaporation is a phase change that occurs at the surface of a liquid and is influenced by factors such as temperature, surface area, and the presence of air currents.
7.
Butter going soft and runny on a hot day is an example of
Correct Answer
B. Melting
Explanation
On a hot day, the high temperature causes the butter to absorb heat energy from its surroundings. This increase in temperature causes the butter to change from its solid state to a liquid state, resulting in it becoming soft and runny. This process is known as melting, where a substance transitions from a solid to a liquid due to the absorption of heat energy.
8.
What is the missing word? When water is...., it starts to change from a liquid to a solid.
Correct Answer
A. Cooled
Explanation
When water is cooled, it starts to change from a liquid to a solid. Cooling refers to the process of reducing the temperature of a substance, in this case, water, causing it to lose heat energy and transition from a liquid state to a solid state, forming ice.
9.
Clouds are formed by
Correct Answer
C. Water vapour condensing
Explanation
Clouds are formed when water vapor in the air cools and condenses into tiny water droplets or ice crystals. This process occurs when warm air rises and expands, causing it to cool down. As the air cools, it can no longer hold as much water vapor, leading to the condensation of water droplets around tiny particles in the atmosphere. These condensed water droplets then come together to form clouds. Therefore, the correct answer is "water vapor condensing."
10.
We use the same water today that dinosaurs used when they lived on the Earth. Is this true or false?
Correct Answer
A. True
Explanation
This statement is true. Water is a renewable resource and has been on Earth for billions of years. The water cycle ensures that the same water is constantly recycled and reused. This means that the water we use today is the same water that existed during the time of dinosaurs. However, it is important to note that the composition of water may have changed over time due to various factors such as pollution and natural processes.
11.
A gas condenses into a liquid when it is...
Correct Answer
A. Cooled
Explanation
When a gas is cooled, its particles lose energy and slow down. As a result, the attractive forces between the particles become stronger and overcome their kinetic energy, causing them to come closer together. This leads to the formation of a liquid, as the gas condenses into a more compact state.
12.
Which process is the opposite of condensation?
Correct Answer
C. Evaporation
Explanation
Evaporation is the process in which a liquid changes into a gas, while condensation is the process in which a gas changes into a liquid. Therefore, evaporation is the opposite of condensation. Melting and freezing are processes that involve the change of state from solid to liquid and liquid to solid respectively, and are not directly related to condensation.
13.
Which of these statements is FALSE?
Correct Answer
B. Evaporation only happens at 100°C
Explanation
Evaporation is a process in which a liquid changes into a gas state. It occurs at all temperatures, not just at 100°C. The statement that "Evaporation only happens at 100°C" is false. Evaporation is influenced by factors such as temperature, surface area, humidity, and wind. Heat and wind help in increasing the rate of evaporation by providing energy to the liquid molecules and carrying away the water vapor respectively.
14.
The movement of water around and around our world is called...
Correct Answer
B. The water cycle
Explanation
The movement of water around and around our world is referred to as the water cycle. This process involves the continuous circulation of water through various stages, including evaporation, condensation, and precipitation. It is a vital natural process that helps maintain the Earth's water balance and ensures the availability of freshwater for various ecosystems and human activities.
15.
Which of these is NOT a part of the water cycle?
Correct Answer
C. When it rains, the clouds melt
Explanation
When it rains, the clouds do not melt. Instead, the water droplets in the clouds combine and become larger until they are heavy enough to fall as precipitation. This is a crucial part of the water cycle as it replenishes the Earth's water supply.