2nd Grade Science
What is Matter?
Unit 3
Unit 3: What is Matter and How Does it Change?
Matter
What is matter?
Matter is anything and everything. If it takes up space and has mass, it is matter.
But...what's mass?
Mass is the amount of matter in an object. Confusing, right? Let's think of matter as "stuff" (it's really atoms), so mass is the measure of the amount of "stuff" in an object.
Properties of Matter
Other than mass, there are many properties (traits or qualities) of matter.
- color
- length: how long it is
- hardness: how difficult it is to scratch or break
- texture: how it feels
- absorbency: how much it is able to soak up water
Look how much this soaks up the blue liquid! It is very absorbent.
We can use texture to describe matter, like how smooth or rough something is.
States of Matter
We put matter into groups based on their state - whether they're a solid, liquid, or a gas. There's actually other states (like plasma), but we won't worry about them right now.
Changing the State of Matter
We can change the state of matter by adding energy to it, like heat. By heating it up, we can change it from a solid to a liquid, a liquid to a gas, and so on!
Ever had the ice in your drink melt? That's because it warmed up! Ice is the solid form of water. By heating it up, we can change its state of matter to a liquid.
Water, in its liquid (or regular) state, can be changed to a gas by adding heat. This is what happens when we boil water - we add heat to it, and steam forms. Steam is water in the gas state.
We can also change the state of matter by taking energy away from it, by cooling it down. This does the opposite of what heating matter does. For example, when you cool down a gas, like steam, you turn it back into a liquid!
Ever noticed your cold glass of water gets wet on the outside after a while? This is because hot air (which has steam in it) hits the cold glass. The cold glass cools down the air, turning it into a liquid. That's why your glass gets wet.
Quick Quiz!
How many states of matter do you see in this picture?
You should see 2. This is called a hot spring. There is liquid water, and steam (gas) rising off of it.
Permanent Changes
When we heat or cool down certain substances, like water, we can reverse the change. For example, if we cool down water to its solid form, ice, we can turn it back into liquid water by heating it again. Some changes, on the other hand, can't be taken back.
Watch this video lab and see how some changes are reversible, and some aren't. Then, answer the questions down below.
Is mixing cement and water a reversible change?
No. When you mix cement and water, it sets to make hard concrete. You can't turn concrete back into cement and water, so the change is not reversible.
Is mixing baking soda and vinegar a reversible change?
No. When you mix baking soda and vinegar, they react and form bubbles. The two substances become one new substance, and you can't turn it back into baking soda and vinegar. Bubbles are a good sign of an irreversible, or not reversible, change.
Is burning a reversible change?
No. When you burn something, like wood, you permanently change it. Burning wood makes ash. You can never turn ash back into wood.
A change is called irreversible if it cannot be changed back again.
In an irreversible change, new materials are always formed. Sometimes these new materials are useful to us.
For example, when we cook a raw egg by heating it, we cannot turn the cooked egg back into a raw one. This change is irreversible.
