Sycamore High Physical Science - Chapter 2

Front 1

Pure Substance

Back 1

Matter that always has exactly the same composition. Every sample of a given substance has the same properties because a substance has a fixed, uniform composition.

Front 2

Element

Back 2

A substance which cannot be broken down into simpler substances.

Front 3

Atom

Back 3

The smallest particle of an element. An element has a fixed composition because it contains only one type of atom.

Front 4

Compound

Back 4

A substance that is made from two or more simpler substances and can be broken down into those simpler substances. The simpler substances can be either elements or compounds. A compound always contains two or more elements joined in a fixed proportion.

Front 5

Mixtures

Back 5

A mixture is what you get when you combine two substances in such a way that no chemical reaction occurs between the substances and you can separate them again.

Front 6

Heterogenous Mixtures

Back 6

The parts of a mixture are noticeably different from each other. An example of a heterogenous mixture would be salsa or a fruit salad.

Front 7

Homogenous Mixtures

Back 7

The substances in the mixture are evenly distributed so it is difficult to distinguish one substance from another. Air and water are examples of homogenous mixtures.

Front 8

Classification of Mixtures Based on Particle Size

Back 8

1. Solution (smallest particle size)

2. Colloid (medium particle size)

3. Suspension (largest particle size)

Front 9

Solution

Back 9

When substances dissolve and form a homogenous mixture. Liquid solutions do not separate into distinct layers over time. Vinegar is an example of a solution.

Front 10

Suspension

Back 10

A heterogeneous mixture that separates into layers over time. Muddy water is an example of a suspension.

Front 11

Colloid

Back 11

A colloid is a mixture that contains particles that are intermediate in size between the small particles in a solution and large particles in a suspension. Colloids do not separate into layers. Homogenized mil is an example of a colloid.

Front 12

Physical Property

Back 12

Any characteristic of a material that can be observed or measured without changing the composition of the substances in the material.

Physical properties include viscosity, conductivity, malleability, hardness, melting point, boiling point, and density.

Front 13

Viscosity

Back 13

A liquid's resistance to flowing. The higher the viscosity, the slower the liquid moves. For example, honey is more viscous than water.

Front 14

Conductivity

Back 14

A material's ability to allow heat to flow. If a material is a good conductor of heat, it is usually also a good conductor of electricity.

Front 15

Malleability

Back 15

The ability of a solid to be hammered without shattering. Most metals are malleable.

Front 16

Hardness

Back 16

A material's hardness is its ability to resist being scratched by another material.

Front 17

Melting Point

Back 17

The temperature at which a substance changes from a solid to a liquid.

Front 18

Boiling Point

Back 18

The temperature at which a substance changes from a liquid to a gas.

Front 19

Density

Back 19

Density is the ratio of the mass of a substance to its volume.

Density (D) = mass (M) / Volume (V)

Front 20

Using Physical Properties

Back 20

Physical properties are used to identify a material, to choose a material for a specific purpose, or to separate the substances in a mixture.

Front 21

Filtration

Back 21

Filtration is a process that separates materials based on their particle size. Using a strainer is an example of filtration.

Front 22

Distillation

Back 22

Distillation is a process that separates substances based on their boiling points. Boiling seawater to separate fresh water is an example of distillation.

Front 23

Physical Change

Back 23

A physical change occurs when some of the properties if a material change, but the substances in the material remain the same. Crumpling a piece of paper and melting a stick of butter are examples of physical changes.

Front 24

Chemical Property

Back 24

Any ability to produce a change in the composition of matter. Chemical properties can be observed only when the substances in a sample of matter are changing into different substances. Flammability and reactivity are examples of chemical properties.

Front 25

Flammability

Back 25

Flammability is a material's ability to burn in the presence of oxygen.

Front 26

Reactivity

Back 26

Reactivity describes how readily a substance combines with other substances. Oxygen reacts with iron and water to form rust.

Front 27

Chemical Change

Back 27

A chemical change occurs when a substance reacts and forms one or more new substances.

Front 28

Evidence of Chemical Changes

Back 28

1. Change in color

2. Production of a gas

3. Formation of a precipitate

Front 29

Precipitate

Back 29

Any solid that forms and separates from a liquid mixture.

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Front 30

Chemical vs. Physical Change

Back 30

When matter undergoes a chemical change, the composition of the matter changes. When matter undergoes a physical change, the composition of the matter stays the same.