Unit 2 Matter — Study Guide

matter

Anything that takes up space.

Tip: If it takes up space, it is matter — solids, liquids, and gases all count. Air is matter too!

Example: a rock, water in a cup, and air inside a balloon.

melting point

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

Tip: Think “melt” = solid → liquid. Ice’s melting point is 0°C (32°F).

freezing point

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

Tip: Freezing is the opposite of melting (liquid → solid). For water, freezing point is also 0°C.

physical properties

Anything you can observe about an object using one or more senses.

Tip: Look, touch, smell — color, hardness, shininess, weight, volume, magnetism, conductivity, solubility.

Example: a metal soup can looks shiny, hard, and reflective.

conservation of matter

The law that matter cannot be made or destroyed; matter can change into a new form.

Tip: Crush cookies, melt ice, or freeze water — the amount of matter stays the same.

Example: 36 g of cookies pushed into a ball still have 36 g. 50 g ice + 75 g water frozen → 125 g ice.

physical change

Shape or form changes, but the substance keeps the same chemical makeup.

Tip: Tear paper, melt ice, or dissolve sugar — you can often get the original substance back.

boiling point

The point at which matter changes from a liquid to a gas.

Tip: Water boils at 100°C (212°F) at sea level — liquid water → water vapor (gas).

mixture

A combination of two or more different substances that keep their identities.

Tip: You can usually separate the parts. Cereal + milk or spaghetti + sauce + meatballs = mixtures.

chemical change

A change caused by a reaction that forms new and different substances.

Tip: Look for clues like rust, burning, or a new color that won’t wash off. A shovel turning reddish in damp soil has rusted.

solution

A mixture with the same composition throughout because all parts are mixed evenly.

Tip: Sugar stirred into water until even is a solution. Metals mixed into an alloy can also be a solution. After water evaporates, sugar is left behind.

2. What is matter? Weight & more matter

Key ideas

Matter is anything that takes up space.
As matter is added to an object, its weight increases.
On a pan balance, the heavier object has more matter / more weight.
Best demo that air takes up space: blow up a balloon, tie it, and try to flatten it.

3. States of matter (solid / liquid / gas)

Compare the three states

Solid — definite shape and definite volume (example: ice). Particles are tightly packed in an ordered grid. A solid has its own shape.
Liquid — definite volume, but takes the shape of its container (example: liquid water).
Gas — no definite shape and no definite volume / does not take up a definite amount of space (example: water vapor).

Changing state (melting, freezing, boiling, evaporating) does not create or destroy matter — matter is neither lost nor gained.

4. Physical properties

What you can observe

Mass / weight — measured with a pan balance or scale.
Volume — measured with a graduated cylinder; for a rock, use water displacement (watch the water rise).
Conductivity — metals (like a metal fork) often conduct electricity; wood and plastic usually do not.
Solubility — demo: pour salt into water and see if it dissolves.
Other examples: magnetism, hardness, shininess / reflective surface.

5. Mixtures vs solutions vs alloys

Keep these straight

A mixture combines substances that keep their identities (spaghetti + sauce + meatballs; cereal + milk). No new substance forms; you can often separate the parts.
A solution is a special mixture mixed evenly throughout (sugar in water; metals in an alloy).
If sugar water evaporates, the sugar is left behind — it was not destroyed.

6. Physical vs chemical change

How to tell them apart

Physical change — shape or form changes; same substance (crushing, melting, freezing, dissolving, tearing).
Chemical change — a reaction makes new substances (rusting, burning).
Reddish shovel in damp soil → rusted (chemical change).

7. Conservation of matter

Matter is conserved

Matter cannot be made or destroyed; it can change form.
Cookies reshaped: mass stays the same.
Ice + liquid water frozen together: add the masses (50 g + 75 g = 125 g).
When water evaporates from a container, the remaining liquid’s weight and volume decrease (some water left as gas/vapor).
Changing states: matter is neither lost nor gained.

1. Vocabulary (10 terms)

matter

melting point

freezing point

physical properties

conservation of matter

physical change

boiling point

mixture

chemical change

solution

2. What is matter? Weight & more matter

Key ideas

3. States of matter (solid / liquid / gas)

Compare the three states

4. Physical properties

What you can observe

5. Mixtures vs solutions vs alloys

Keep these straight

6. Physical vs chemical change

How to tell them apart

7. Conservation of matter

Matter is conserved