Measuring Matter

Measuring Matter

Middle School

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Learning Objectives

Key Vocabulary

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Mass

Mass is the amount of matter in an object; it remains constant regardless of its location.

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Weight

Weight is the force of gravity acting on an object; it changes depending on the location.

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Volume

Volume is the total amount of space that a specific object or a substance actually occupies.

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Density

Density is the mass of a substance per unit of volume, a key property for identification.

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Physical Property

This is a characteristic of a substance that can be observed without changing its chemical identity.

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Chemical Property

This property becomes evident during a chemical reaction, as the substance's chemical identity changes.

Key Vocabulary

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Chemical Reaction

A chemical reaction is a process that results in the formation of new chemical substances.

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Melting Point

The melting point is the specific temperature at which a solid substance turns into a liquid.

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Boiling Point

The boiling point is the specific temperature at which a liquid substance turns into a gas.

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Solubility

Solubility describes the ability of a solid, liquid, or gas to dissolve in a solvent.

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Flammability

Flammability is the property of a substance that describes how easily it can burn or ignite.

Mass, Weight, and Volume

• Mass is the amount of matter in an object and is always constant.

• Weight is the measure of gravity's force and can change with location.

• Volume is the space matter occupies, measured in cm³ or mL.

Multiple Choice

Which statement best defines an object's mass?

• The amount of matter in an object.

• The force of gravity pulling on an object.

• The amount of space an object takes up.

• The object's shape and texture.

Multiple Choice

What is the key difference between mass and weight?

• Mass is constant regardless of location, while weight depends on gravity.

• Mass is measured in mL, while weight is measured in cm3.

• Mass depends on an object's volume, while weight does not.

• Mass and weight are two different words for the same property.

Multiple Choice

An astronaut takes a rock from Earth to the Moon, which has much lower gravity. What will happen to the rock's properties?

• The rock's weight will decrease, but its mass and volume will stay the same.

• The rock's mass will decrease, but its weight and volume will stay the same.

• The rock's volume will increase, but its mass and weight will stay the same.

• The rock's mass, weight, and volume will all decrease.

How to Measure Volume

• For regular shapes, measure length, width, and height to find the volume.

• For irregular shapes, use the water displacement method to determine the volume.

• The volume of displaced water equals the volume of the submerged object.

Multiple Choice

What key characteristic of an object determines which method should be used to measure its volume?

• Its mass

• Its shape

• Its color

• Its texture

Multiple Choice

When using the water displacement method, what is the relationship between a submerged object and the water it displaces?

• The volume of the displaced water is equal to the volume of the object.

• The volume of the displaced water is less than the volume of the object.

• The volume of the displaced water is greater than the volume of the object.

• The volume of the displaced water is unrelated to the volume of the object.

Multiple Choice

A student calculates that a rectangular box has a volume of 24 cm³. They then use water displacement and find that a rock has a volume of 20 cm³. Which object has a greater volume and why?

• The rock, because it is an irregular shape.

• The box, because its calculated volume is greater.

• They both have the same volume.

• It is impossible to tell without weighing them.

Understanding Density

• Density is how much mass fits into a specific volume.

• To calculate density, you divide the mass of an object by its volume.

• An object's density determines if it will sink or float in water.

Multiple Choice

What is the definition of density?

• A measure of how much mass is contained in a specific volume.

• The total weight of an object on a scale.

• The amount of space an object occupies.

• The force of gravity acting on an object.

Multiple Choice

How is the density of an object calculated?

• By multiplying the object's mass by its volume.

• By dividing the object's mass by its volume.

• By adding the object's mass to its volume.

• By dividing the object's volume by its mass.

Multiple Choice

If two objects have the exact same volume, but one has more mass than the other, what can you conclude?

• The object with more mass will have a higher density.

• The object with more mass will have a lower density.

• Both objects will have the same density.

• The density cannot be determined without knowing the exact mass.

How Temperature Affects Density

• Heating makes most substances expand, decreasing their density.

• Cooling makes most substances contract, increasing their density.

• Water peaks in density at 4°C; freezing makes ice less dense.

Multiple Choice

What is the general relationship between heating a substance and its density?

• It decreases because the substance expands.

• It increases because the substance expands.

• It decreases because the substance contracts.

• It stays the same regardless of temperature.

Multiple Choice

How does the density of water change when it freezes into ice?

• It becomes less dense.

• It becomes more dense.

• Its density does not change.

• It reaches its peak density.

Multiple Choice

A solid block of wax sinks in liquid wax. Based on the principles of density, what will a block of ice do in liquid water and why?

• The ice will float because water is less dense as a solid than as a liquid.

• The ice will sink because cooling makes substances more dense.

• The ice will float because all solids are lighter than all liquids.

• The ice will sink because it is colder than the water.

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Physical vs. Chemical Properties

Physical Properties

• ​Characteristics observed or measured without changing the substance's identity.

• ​​These properties describe the substance itself, such as its color, density, or melting point.

• ​For example, an ice cube melting into water is a change in physical state.

Chemical Properties

• ​These properties describe how a substance can transform into a completely new substance.

• ​​They are only observable during a chemical reaction, which creates new materials.

• ​An example is flammability, as seen when wood burns and turns into ash and smoke.

Multiple Choice

Which statement best defines a physical property?

• A characteristic that can be observed or measured without changing the substance's identity.

• A property that describes how a substance can become a new substance.

• A characteristic that is only visible during a chemical reaction.

• A property that describes how a substance burns or rusts.

Multiple Choice

What is the key difference between how physical and chemical properties are observed?

• Physical properties describe color and density, while chemical properties describe melting and boiling.

• Physical properties can be observed without a chemical reaction, while chemical properties can only be observed during one.

• Physical properties involve a change in state, while chemical properties involve a change in color.

• Physical properties create new materials, while chemical properties do not.

Multiple Choice

Based on the provided information, which statement best explains the difference between an ice cube melting and wood burning?

• The melting of an ice cube is a physical change because the substance (water) does not change its identity, while burning wood is a chemical change because it creates new substances (ash and smoke).

• Melting is a chemical change because it requires energy, while burning is a physical change because the wood gets smaller.

• Both are chemical changes because the appearance of the original substance is altered in both scenarios.

• Both are physical changes because they are just changes in the state of matter.

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Using Properties to Identify Substances

• Every pure substance has its own unique set of characteristic properties.

• These properties act like a fingerprint to help identify the substance.

• To identify a substance, measure its properties and compare to known values.

• Gold has a density of 19.3 g/cm³ and melts at 1,064°C.

Multiple Choice

What is the primary purpose of using a substance's unique physical and chemical properties?

• To determine the identity of the substance.

• To change the substance into a new one.

• To increase the amount of the substance.

• To mix the substance with other things.

Multiple Choice

Why are the properties of a pure substance often compared to a fingerprint?

• They are unique to each substance and can be used for identification.

• They can be easily changed with little effort.

• They are identical for all substances under the same conditions.

• They describe the substance's color and shape only.

Multiple Choice

A student has a sample of an unknown metal. After measuring its density and melting point, what is the next logical step to identify the substance?

• Compare the measured properties to a list of known values for different substances.

• Assume the substance is water since it has no color.

• Mix the sample with gold to see if it changes.

• Measure the melting point of the substance and ignore its density.

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Identifying a Chemical Reaction

• A chemical reaction occurs when atoms rearrange to form completely new substances.

• ​Scientists analyze properties of substances before and after they interact to identify reactions.

• The new substances formed have different properties from the original substances.

• Burning steel wool creates a new, brittle powder, indicating a chemical reaction.

Multiple Choice

What is the primary result of a chemical reaction?

• They are rearranged to create entirely new substances.

• They are permanently destroyed and vanish.

• They are mixed together but keep their original properties.

• They are changed into a different state of matter, like melting.

Multiple Choice

How can scientists determine that a chemical reaction has created a new substance?

• By measuring the temperature of the substances.

• By seeing if the substances have mixed together.

• By comparing the properties of the substances before and after.

• By checking the initial color of the substances.

Multiple Choice

When steel wool is burned, it changes from a flexible metal to a brittle, dark powder. What is the best conclusion from this observation?

• The steel wool underwent a physical change, like melting.

• A chemical reaction occurred because a new substance with different properties was formed.

• The steel wool simply got dirty from the heat.

• The atoms in the steel wool were destroyed by the fire.

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Common Misconceptions

Misconception	Correction
Mass and weight are the same.	Mass is the amount of matter, while weight is the force of gravity.
Any change to a substance is a chemical reaction.	A physical change alters the state; a chemical reaction creates a new substance.
Heavy objects are denser than light objects.	Density is a ratio of mass to volume, not just weight.
Ice is denser than water because it is a solid.	Ice is less dense than its liquid form, which is why it floats.

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Summary

Poll

On a scale of 1-4, how confident are you about calculating mass, volume, and density?

• 1

• 2

• 3

• 4