Physical and Chemical Changes

Physical Changes

1) Physical changes affect the physical properties of matter, (things like size, shape, appearance) but the substance is still the same substance. -ripping paper -changes of state -dissolving -crushing -cutting

2) ALL changes of state are physical changes A change of state is the change of a substance from one physical form to another

3) During a change of state, the energy of a substance changes, and particles speed up or slow down. speed up or slow down a)If energy is added to particles they speed up and spread out b) If energy is removed, particles slow down and come closer together.

4) Melting: change from a solid to a liquid. a) The temperature at which a substance will melt is called the “melting point.”

4b) When a solid absorbs more energy the particles will move faster and as they overcome their attraction to each other they transform into a liquid. Energy added – particles speed up and spread out

5) Freezing: change from a liquid to a solid. a)The temperature at which a substance will freeze is called its freezing point. b) The melting point and freezing point of a substance are the same temperature. In at least two sentences explain why the melting point and freezing point are the same temperature

5c) When liquids cool, they lose energy and the particles slow down and their attraction overcomes motion, and they become locked together to form a solid. Energy removed – particles slow down and come closer together

Turn to your neighbor and explain how melting and freezing occur because energy is transferred. Write at least two sentences in your notes explaining this.

6) Vaporization: change from a liquid to a gas. there are two types - boiling and evaporation a) boiling: liquid becomes gas throughout the liquid b) evaporation: liquid becomes gas only on the surface of the liquid

7) Condensation: change from gas to liquid a- energy is removed, and particles slow down b- condensation point – temperature at which gas will become liquid

Turn to your neighbor and explain how condensation and evaporation occur because energy is transferred. Write at least two sentences in your notes explaining this.

8) Sublimation: change from a solid directly to a gas

Copy the following diagram and fill in the appropriate term in the arrows solid liquidgas

9) Other physical changes include ripping, cutting, crushing and dissolving. a) When one substance is dissolved in another the particles of each are mixed together, but NOT bonded together to make a new substance.

Mixtures

1) A mixture is a combination of two or more substances that are not chemically combined, they are combined physically. Video Link

2) Substances in a mixture retain their identities and properties. Mixtures are created through physical changes.

When two things are combined in a mixture, they come out the same as they go in + += Mixing these two together did not change them into other things

3)The common types of mixtures: a) solutions b) suspensions c) colloids

Chemical Changes

1) Chemical changes: one or more substances are changed into an entirely new substance with different properties.

2) Clues to chemical change: a) color changes b) fizzing or foaming c) heat changes d) production of sound, light, color 3) Chemical changes cannot be undone using normal physical processes.

4) In a chemical change, the items that combine together are called reactants, the resulting substance is called a product Reactants React together….. Products are Produced +

5) The law of conservation of matter (mass) tells us that in any chemical reaction the mass of the products must always equal the mass of the reactants and that the same number of atoms of each element must occur on each side of an equation.

3-2-1: Write the following things in your notes: 3 -indicators of a chemical change 2 – names for objects in a chemical reaction 1 – law that explains what happens in a chemical reaction

Which type of change? ACTION TAKING PLACE PHYSICAL OR CHEMICAL Glass breaking Ice cube melting Candle burning Food digested in your stomach Glass breaking Marshmallow burning Lake freezing Bread baking Sugar dissolving Popsicle melting Gasoline burned in an engine Lake freezing

Compounds

1) A compound is a pure substance composed of two or more elements that are chemically combined. Ex: water, salt Compounds are considered pure, because each particle of NaCl is identical to every other particle of NaCl Water is considered pure. Even though it is made of both hydrogen and oxygen; each molecule of water is exactly the same as any other molecule of water.

2) Compounds are created through a chemical change and can be broken down through a chemical change + =

2) When two things are combined to make a compound, they come out as something completely different + =

3) Elements in a compound are combined in a specific ratio – each group of atoms bonded together is called a molecule. All the particles are the same so it is a pure substance Carbon dioxide (CO 2 ) will always have 2 atoms of oxygen for every one atoms of carbon