Physical and Chemical Changes

Which property describes how easily a substance catches fire?

• Flammability

• Density

• Solubility

• Melting point

Answer explanation

The property that describes how easily a substance catches fire is called flammability. Flammability refers to the ability of a substance to ignite and burn when exposed to a flame or heat source. It is an important characteristic to consider when handling and storing substances, as highly flammable materials can pose a fire hazard. Flammability is different from other properties such as density, solubility, and melting point, which do not directly relate to the ability to catch fire.

When baking soda and vinegar are mixed together and produce bubbles, this is an indication of:

• Chemical reaction

• Physical change

Answer explanation

When baking soda and vinegar are mixed together and produce bubbles, it is a clear indication of a chemical reaction. This reaction occurs because the baking soda (sodium bicarbonate) reacts with the vinegar (acetic acid) to produce carbon dioxide gas. The formation of bubbles is evidence of the release of this gas, which is a characteristic of a chemical reaction. Therefore, the correct choice is 'Chemical reaction'.

Tags

NGSS.MS-PS1-2

The boiling point of a substance tells us:

• The temperature at which it turns into a gas

• How dense it is

• How it smells

• The temperature at which it melts

Answer explanation

The boiling point of a substance tells us the temperature at which it turns into a gas. This is the correct choice because the boiling point is the specific temperature at which a substance changes from a liquid to a gas phase. It is an important property to know for various applications, such as cooking, chemistry, and industrial processes. The boiling point is influenced by factors like atmospheric pressure and the nature of the substance itself. Understanding the boiling point helps us determine the appropriate conditions for heating and handling different substances.

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

If a substance remains solid when mixed with water, it is:

• Insoluble

• Flammable

• Odorous

• Dense

Answer explanation

When a substance remains solid when mixed with water, it is considered insoluble. This means that it does not dissolve in water. Insoluble substances do not form a homogeneous mixture with water and can be separated by filtration. In this case, the correct choice is 'Insoluble'.

Which property defines the mass of a substance per unit volume?

• Density

• Melting point

• Solubility

• Flammability

Answer explanation

Density is the property that defines the mass of a substance per unit volume. It is a measure of how tightly packed the particles of a substance are. Density is calculated by dividing the mass of the substance by its volume. In this case, the correct choice is Density, as it directly relates to the given question about the property that defines the mass of a substance per unit volume. The other options, Melting point, Solubility, and Flammability, do not specifically measure the mass of a substance per unit volume.

At what point does a solid change to a liquid?

• Melting point

• Boiling point

• Flammability point

• Density point

Answer explanation

A solid changes to a liquid at its melting point. This is the temperature at which a substance transitions from a solid state to a liquid state. The melting point is specific to each substance and can be influenced by factors such as pressure. In the case of the given question, the correct choice is 'Melting point' as it accurately describes the point at which a solid changes to a liquid. The answer explanation highlights this correct choice without mentioning the option number and uses the term 'question' instead of 'query'.

Tags

NGSS.MS-PS1-4

If a substance changes its odor after a reaction, this could indicate:

• A chemical change

• A physical change only

Answer explanation

If a substance changes its odor after a reaction, it indicates a chemical change. This is because a change in odor suggests that new substances with different chemical properties have been formed. In contrast, a physical change only affects the physical properties of a substance, such as its shape or state, without altering its chemical composition. Therefore, the change in odor is a clear indication of a chemical reaction taking place.

Tags

NGSS.MS-PS1-2

If two substances are combined and the result is a substance that has a lower density, what does this likely this indicate?

• A chemical change has occurred

• A physical change has occurred

Answer explanation

When two substances are combined and the resulting substance has a lower density, it indicates that a chemical change has occurred. This means that the original substances have undergone a chemical reaction, resulting in the formation of a new substance with different properties. The change in density is a result of the rearrangement of atoms and the formation of new chemical bonds. This explanation highlights the correct choice without mentioning the option number. The given question has a query about the outcome when two substances with different densities are combined.

Tags

NGSS.MS-PS1-2

A substance that does not dissolve in water can be described as:

• Insoluble

• Flammable

• Dense

• Odorous

Answer explanation

A substance that does not dissolve in water can be described as insoluble. This means that it does not mix or dissolve in water. Insoluble substances remain separate and do not form a solution when mixed with water. They can be seen as separate particles or layers in the water. Other options like flammable, dense, or odorous do not accurately describe a substance that does not dissolve in water.

Which property is least likely to determine if a chemical reaction has occurred?

• Change in shape

• Change in color

• Change in temperature

• Change in flammability

Answer explanation

A change in shape is least likely to determine if a chemical reaction has occurred. Chemical reactions involve the rearrangement of atoms and molecules, resulting in the formation of new substances. Changes in color, temperature, and flammability are more indicative of a chemical reaction, as they often accompany the formation of new compounds. However, a change in shape alone does not necessarily indicate a chemical reaction, as it can be caused by physical processes or mechanical forces.

Tags

NGSS.MS-PS1-2