Chapter 5 - Unit review

what is the particle theory of matter?

All matter is made up of tiny particles that are always moving. 

what’s a pure substance?

Only one kind of particle (like gold or water). 

what’s a mixture?

Two or more substances  mixed together but not chemically joined. 

what is a mechanical mixture?

(heterogeneous): You can see the different parts (like salad or trail mix). 

what is a solution?

(homogeneous): Looks like one thing but has more than one substance mixed evenly (like salt water). 

what is an alloy?

A mixture of metals (like steel or bronze). 

what is a physical property?

Something you can observe or measure without changing what it is (like colour or shape). 

what is a qualitative property?

A property you can measure (like mass, volume, or temperature). 

what is a quantitative property?

A property you describe (like colour, smell, or texture). 

what is a characteristic physical property?

A special property that helps identify a substance (like density or melting point). 

what’s density?

How much mass is in a certain space (mass divided by volume). 

what’s a chemical property?

How a substance reacts with others (like flammability or rusting). 

what is a physical change?

The substance stays the same, but it looks different (like melting or cutting).

what’s a chemical change?

The substance changes into something new (like burning or rusting).

what is precipitate?

A solid that forms when two liquids react. 

classify matter.

We group matter as pure substances or mixtures.

How are properties used to describe and identify different substances?

We use physical properties and chemical properties to tell substances apart. 

Understanding the clues for physical and chemical change?

Physical changes changes appearance; chemical changes making new substances, bubbles, colour change or heat/light.

Simple chemical tests can identify common gases.

We can use easy tests to tell gases apart like seeing how they react with fire or other chemicals. 

Safety in science?

Always wear goggles, follow instructions, and don't touch or smell unknown chemicals.